html5/spec-ja/workers-non-normative.ja.html.u8


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  <title>Web Workers</title>
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   <p class="no-ja-translation"><a class=logo href="http://www.whatwg.org/" rel=home><img alt=WHATWG
    src="/images/logo"></a></p>

   <h1 id=web-workers class="no-ja-translation">Web Workers</h1>

   <h2 class="no-num no-toc has-ja-translation" id=draft><span class=en-original lang=en>Draft Recommendation &mdash; 27 August
    2008</span><span class=ja-translation lang=ja>勧告案<ins class=ja-note>の非公式和訳</ins> &mdash; 
<ins class=ja-note>(原文出版日)</ins> 2008年8月27日</span></h2>

   <p class="no-ja-translation">You can take part in this work. <a
    href="http://www.whatwg.org/mailing-list">Join the working group's
    discussion list.</a></p>

   <p class="has-ja-translation"><span class=en-original lang=en><strong>Web designers!</strong> We have a <a
    href="http://blog.whatwg.org/faq/">FAQ</a>, a <a
    href="http://forums.whatwg.org/">forum</a>, and a <a
    href="http://www.whatwg.org/mailing-list#help">help mailing list</a> for
    you!</span><span class=ja-translation lang=ja><strong>Web デザイナーのみなさん!</strong> みなさんのための <a
    href=http://blog.whatwg.org/faq/ lang=en>FAQ</a>、<a
    href=http://forums.whatwg.org/>掲示板</a>、<a
    href=http://www.whatwg.org/mailing-list#help>ヘルプ用メイリング・リスト</a>があります!

</span><p>

<!-- Japanese-translation-only notes -->
<ins class="ja-note cover-ja-note" lang=ja>
<p>この文書は、 WHATWG 仕様書の日本語訳です。
正式な仕様書は英語版だけであり、
この日本語訳はあくまで参考としてご利用ください。

<p lang=en>This document is a Japanese translation of
the WHATWG HTML5 specification.  Note that the only normative specification
for the HTML5 is the original English version and this Japanese
translation is non‐normative.

<p>日本語訳は <a href="edit/" rel=edit>Web 界面</a>を使って編集できます。
編集結果はおよそ3時間おきに反映されます。
また、原文の変更には毎日自動的に追随しています。

<p lang=en>The Japanese text can be edited using the <a href=edit/ rel=edit>Web
interface</a>.  Any modifications will be reflected to this translation
in about three hours.  Note that any changes to the original specification
will automatically be incorporated to this translation every day.

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<p><span><!-- dummy --></span></p>

   <dl>
    <dt class="has-ja-translation"><span class=en-original lang=en>This version:

    </span><span class=ja-translation lang=ja><ins class=ja-note>原文の</ins>この版</span><dd class="no-ja-translation"><a
     href="http://www.whatwg.org/specs/web-workers/current-work/">http://whatwg.org/ww</a>

    <dt class="has-ja-translation"><span class=en-original lang=en>Version history:

    </span><span class=ja-translation lang=ja><ins class=ja-note>原文の</ins>改版履歴:</span><dd class="no-ja-translation">Twitter messages (non-editorial changes only): <a
     href="http://twitter.com/WHATWG">http://twitter.com/WHATWG</a>

    <dd class="no-ja-translation">Commit-Watchers mailing list: <a
     href="http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org">http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org</a>

    <dd class="has-ja-translation"><span class=en-original lang=en>Interactive Web interface: <a
     href="http://html5.org/tools/web-workers-tracker">http://html5.org/tools/web-workers-tracker</a>

    </span><span class=ja-translation lang=ja>対話的 <span lang=en>Web</span> 界面: <a href="http://html5.org/tools/web-workers-tracker">http://html5.org/tools/web-workers-tracker</a></span><dd class="has-ja-translation"><span class=en-original lang=en>Subversion interface: <a
     href="http://svn.whatwg.org/webworkers/">http://svn.whatwg.org/webworkers/</a>

    </span><span class=ja-translation lang=ja><span lang=en>Subversion</span> 界面: <a href="http://svn.whatwg.org/webworkers/">http://svn.whatwg.org/webworkers/</a></span><dt class="has-ja-translation"><span class=en-original lang=en>Issues:

    </span><span class=ja-translation lang=ja>問題:</span><dd class="no-ja-translation">To send feedback: <a
     href="http://www.whatwg.org/mailing-list">[email protected]</a>

    <dd class="no-ja-translation">To view and vote on feedback: <a
     href="http://www.whatwg.org/issues/">http://www.whatwg.org/issues/</a>

    <dt class="has-ja-translation"><span class=en-original lang=en>Editor:

    </span><span class=ja-translation lang=ja>編集者:</span><dd class="no-ja-translation">Ian Hickson, Google, [email protected]
   </dl>

   <p class="copyright no-ja-translation">&copy; Copyright 2004-2008 Apple Computer, Inc.,
    Mozilla Foundation, and Opera Software ASA.</p>

   <p class="copyright no-ja-translation">You are granted a license to use, reproduce and create
    derivative works of this document.</p>
  </div>

  <hr>

  <h2 class="no-num no-toc has-ja-translation" id=abstract><span class=en-original lang=en>Abstract</span><span class=ja-translation lang=ja>概要</span></h2>

  <p class="has-ja-translation"><span class=en-original lang=en>This specification defines an API that allows Web application authors to
   spawn background workers running scripts in parallel to their main page.
   This allows for thread-like operation with message-passing as the
   coordination mechanism.

  </span><span class=ja-translation lang=ja>この仕様書は、 Web アプリケーションで、主たる頁とは並列に、
背景労働者スクリプトを走らせるための API を定義します。
これにより、メッセージ・パッシングによるスレッド的操作を協調機構として利用できるようになります。</span><h2 class="no-num no-toc has-ja-translation" id=status><span class=en-original lang=en>Status of this document</span><span class=ja-translation lang=ja>この文書の状態</span></h2>

  <p class="no-ja-translation"><strong>This is a work in progress!</strong> This document is changing
   on a daily if not hourly basis in response to comments and as a general
   part of its development process. Comments are very welcome, please send
   them to <a href="mailto:[email protected]">[email protected]</a>. Thank
   you.

  <p class="has-ja-translation"><span class=en-original lang=en>The current focus is in developing a first draft proposal.

  </span><span class=ja-translation lang=ja>現在の焦点は、第1案の開発です。</span><p class="no-ja-translation">Implementors should be aware that this specification is not stable.
   <strong>Implementors who are not taking part in the discussions are likely
   to find the specification changing out from under them in incompatible
   ways.</strong> Vendors interested in implementing this specification
   before it eventually reaches the call for implementations should join the
   <a href="/mailing-list">WHATWG mailing list</a> and take part in the
   discussions.

  <p class="no-ja-translation">This specification is also being produced by the <a
   href="http://www.w3.org/html/wg">W3C HTML WG</a>. The two specifications
   are identical from the table of contents onwards.

  <h2 class="no-num no-toc has-ja-translation" id=contents><span class=en-original lang=en>Table of contents</span><span class=ja-translation lang=ja>目次
</span></h2>
  <!--begin-toc-->

  <ul class=toc>
   <li class="no-ja-translation"><a href="#introduction"><span class=secno>1. </span>Introduction</a>
    <ul class=toc>
     <li class="no-ja-translation"><a href="#tutorial"><span class=secno>1.1 </span>Tutorial</a>
      <ul class=toc>
       <li class="no-ja-translation"><a href="#a-background"><span class=secno>1.1.1 </span>A
        background number-crunching worker</a>

       <li class="no-ja-translation"><a href="#a-worker"><span class=secno>1.1.2 </span>A worker for
        updating a client-side database</a>

       <li class="no-ja-translation"><a href="#worker"><span class=secno>1.1.3 </span>Worker used for
        backgroud I/O</a>

       <li class="no-ja-translation"><a href="#shared"><span class=secno>1.1.4 </span>Shared
        workers</a>

       <li class="no-ja-translation"><a href="#delegation"><span class=secno>1.1.5
        </span>Delegation</a>

       <li class="no-ja-translation"><a href="#providing"><span class=secno>1.1.6 </span>Providing
        libraries</a>
      </ul>

     <li class="no-ja-translation"><a href="#conformance"><span class=secno>1.2 </span>Conformance
      requirements</a>
      <ul class=toc>
       <li class="no-ja-translation"><a href="#dependencies"><span class=secno>1.2.1
        </span>Dependencies</a>
      </ul>

     <li class="no-ja-translation"><a href="#terminology"><span class=secno>1.3 </span>Terminology</a>
    </ul>

   <li class="no-ja-translation"><a href="#infrastructure"><span class=secno>2.
    </span>Infrastructure</a>
    <ul class=toc>
     <li class="no-ja-translation"><a href="#the-global"><span class=secno>2.1 </span>The global
      scope</a>
      <ul class=toc>
       <li class="no-ja-translation"><a href="#the-workerglobalscope"><span class=secno>2.1.1
        </span>The <code>WorkerGlobalScope</code> abstract interface</a>

       <li class="no-ja-translation"><a href="#dedicated"><span class=secno>2.1.2 </span>Dedicated
        workers and the <code>DedicatedWorkerGlobalScope</code> interface</a>
        

       <li class="no-ja-translation"><a href="#shared0"><span class=secno>2.1.3 </span>Shared workers
        and the <code>SharedWorkerGlobalScope</code> inteface</a>
      </ul>

     <li class="no-ja-translation"><a href="#base-urls"><span class=secno>2.2 </span>Base URLs and
      origins of workers</a>

     <li class="no-ja-translation"><a href="#the-queue"><span class=secno>2.3 </span>The queue of
      events</a>

     <li class="no-ja-translation"><a href="#the-workers"><span class=secno>2.4 </span>The worker's
      ports</a>

     <li class="no-ja-translation"><a href="#processing"><span class=secno>2.5 </span>Processing
      model</a>

     <li class="no-ja-translation"><a href="#creating"><span class=secno>2.6 </span>Creating
      workers</a>
      <ul class=toc>
       <li class="no-ja-translation"><a href="#the-abstractworker"><span class=secno>2.6.1 </span>The
        <code>AbstractWorker</code> abstract interface</a>

       <li class="no-ja-translation"><a href="#dedicated0"><span class=secno>2.6.2 </span>Dedicated
        workers and the <code>Worker</code> interface</a>

       <li class="no-ja-translation"><a href="#shared1"><span class=secno>2.6.3 </span>Shared workers
        and the <code>SharedWorker</code> interface</a>
      </ul>
    </ul>

   <li class="no-ja-translation"><a href="#apis-available"><span class=secno>3. </span>APIs available
    to workers</a>
    <ul class=toc>
     <li class="no-ja-translation"><a href="#importing"><span class=secno>3.1 </span>Importing scripts
      and libraries</a>

     <li class="no-ja-translation"><a href="#apis-defined"><span class=secno>3.2 </span>APIs defined in
      other specifications</a>

     <li class="no-ja-translation"><a href="#interface"><span class=secno>3.3 </span>Interface objects
      and constructors</a>

     <li class="no-ja-translation"><a href="#worker0"><span class=secno>3.4 </span>Worker locations</a>
      
    </ul>

   <li class="no-num no-ja-translation"><a href="#references">References</a>

   <li class="no-num no-ja-translation"><a href="#acknowledgements">Acknowledgements</a>
  </ul>
  <!--end-toc-->

  <hr>

  <h2 id=introduction class="has-ja-translation"><span class=en-original lang=en><span class=secno>1. </span>Introduction</span><span class=ja-translation lang=ja><span class=secno>1. </span>はじめに</span></h2>

  <h3 id=tutorial class="has-ja-translation"><span class=en-original lang=en><span class=secno>1.1 </span>Tutorial</span><span class=ja-translation lang=ja><span class=secno>1.1 </span>解説</span></h3>

  <p class="has-ja-translation"><span class=en-original lang=en><em>This section is non-normative.</em>

  </span><span class=ja-translation lang=ja><em>この節は規定の一部ではありません。</em></span><p class="has-ja-translation"><span class=en-original lang=en>There are a variety of uses that workers can be put to. The following
   subsections show various examples of this use.

  </span><span class=ja-translation lang=ja>労働者は色々なことに使えます。次の各節では、色々な使い方の例を示します。</span><h4 id=a-background class="has-ja-translation"><span class=en-original lang=en><span class=secno>1.1.1 </span>A background
   number-crunching worker</span><span class=ja-translation lang=ja><span class=secno>1.1.1 </span>数値処理背景労働者</span></h4>

  <p class="has-ja-translation"><span class=en-original lang=en><em>This section is non-normative.</em>

  </span><span class=ja-translation lang=ja><em>この節は規定の一部ではありません。</em></span><p class="has-ja-translation"><span class=en-original lang=en>The simplest use of workers is for performing a computationally
   expensive task without interrupting the user interface.

  </span><span class=ja-translation lang=ja>労働者の一番単純な用法は、計算的に高価な仕事を利用者界面を中断させずに実行することです。</span><p class="has-ja-translation"><span class=en-original lang=en>In this example, the main document spawns a worker to (na&iuml;vely)
   compute prime numbers, and progressively displays the most recently found
   prime number.

  </span><span class=ja-translation lang=ja>この例では、主たる文書が労働者を作って素数を (素朴な方法で) 計算させ、
新しく見つかった素数を順番に表示してゆきます。</span><p class="has-ja-translation"><span class=en-original lang=en>The main page is as follows:

  </span><span class=ja-translation lang=ja>主たる頁は次の通りです。</span><pre class="no-ja-translation">&lt;!DOCTYPE HTML>
&lt;html>
 &lt;head>
  &lt;title>Worker example: One-core computation&lt;/title>
 &lt;/head>
 &lt;body>
  &lt;p>The highest prime number discovered so far is: &lt;output id="result">&lt;/output>&lt;/p>
  &lt;script>
   var worker = new Worker('worker.js');
   worker.onmessage = function (event) {
     document.getElementById('result').textContent = event.message;
   };
  &lt;/script>
 &lt;/body>
&lt;/html></pre>

  <p class="no-ja-translation">The <code title=dom-Worker><a href="#worker2">Worker()</a></code>
   constructor call creates a worker and returns a <code><a
   href="#worker1">Worker</a></code> object representing that worker, which
   is used to communicate with the worker. That object's <code
   title=handler-Worker-onmessage><a href="#onmessage0">onmessage</a></code>
   event handler attribute allows the code to receive messages from the
   worker.

  <p class="has-ja-translation"><span class=en-original lang=en>The worker itself is as follows:

  </span><span class=ja-translation lang=ja>労働者自体は次の通りです。</span><pre class="no-ja-translation">var n = 1;
search: while (true) {
  n += 1;
  for (var i = 2; i &lt;= Math.sqrt(n); i += 1)
    if (n % i == 0)
     continue search;
  // found a prime!
  postMessage(n);
}</pre>

  <p class="no-ja-translation">The bulk of this code is simply an unoptimised search for a prime
   number. To send a message back to the page, the <code
   title=dom-DedicatedWorkerGlobalScope-postMessage><a
   href="#postmessage">postMessage()</a></code> method is used to post a
   message when a prime is found.

  <p class="has-ja-translation"><span class=en-original lang=en><a href="http://www.whatwg.org/demos/workers/primes/page.html">View this
   example online</a>.

  </span><span class=ja-translation lang=ja><a href="http://www.whatwg.org/demos/workers/primes/page.html">この例をオンラインで見る</a>。</span><h4 id=a-worker class="no-ja-translation"><span class=secno>1.1.2 </span>A worker for updating a
   client-side database</h4>

  <p class="has-ja-translation"><span class=en-original lang=en><em>This section is non-normative.</em>

  </span><span class=ja-translation lang=ja><em>この節は規定の一部ではありません。</em></span><p class="no-ja-translation">In this example, the main document spawns a worker whose only task is to
   listen for notifications from the server, and, when appropriate, either
   add or remove data from the client-side database.

  <p class="no-ja-translation">Since no communication occurs between the worker and the main page, the
   main page can start the worker by just doing:

  <pre class="no-ja-translation">&lt;script>
 new Worker('worker.js');
&lt;/script></pre>

  <p class="has-ja-translation"><span class=en-original lang=en>The worker itself is as follows:

  </span><span class=ja-translation lang=ja>労働者自体は次の通りです。</span><pre class="no-ja-translation">var server = new WebSocket('ws://whatwg.org/database');
var database = openDatabase('demobase', '1.0', 'Demo Database', 10240);
server.onmessage = function (event) {
  // data is in the format "command key value"
  var data = event.message.split(' ');
  switch (data[0]) {
    case '+':
     database.transaction(function(tx) {
       tx.executeSql('INSERT INTO pairs (key, value) VALUES (?, ?)', data[1], data[2]);
     });
    case '-':
     database.transaction(function(tx) {
       tx.executeSql('DELETE FROM pairs WHERE key=? AND value=?', data[1], data[2]);
     });
  }
};</pre>

  <p class="no-ja-translation">This connects to the server using the <code>WebSocket</code> mechanism
   and opens the local database (which, we presume, has been created
   earlier). The worker then just listens for messages from the worker and
   acts on them as appropriate, forever (or until the main page is closed).

  <p class="no-ja-translation"><a
   href="http://www.whatwg.org/demos/workers/database-updater/page.html">View
   this example online</a>. (This example will not actually function, since
   the server does not actually exist and the database is not created by this
   sample code.)

  <h4 id=worker class="no-ja-translation"><span class=secno>1.1.3 </span>Worker used for backgroud I/O</h4>

  <p class="has-ja-translation"><span class=en-original lang=en><em>This section is non-normative.</em>

  </span><span class=ja-translation lang=ja><em>この節は規定の一部ではありません。</em></span><p class="no-ja-translation">In this example, the main document uses two workers, one for fetching
   stock updates for at regular intervals, and one for fetching performing
   search queries that the user requests.

  <p class="has-ja-translation"><span class=en-original lang=en>The main page is as follows:

  </span><span class=ja-translation lang=ja>主たる頁は次の通りです。</span><pre class="no-ja-translation">&lt;!DOCTYPE HTML>
&lt;html>
 &lt;head>
  &lt;title>Worker example: Stock ticker&lt;/title>
  &lt;script>
   // TICKER
   var symbol = 'GOOG'; // default symbol to watch
   var ticker = new Worker('ticker.js');

   // SEARCHER
   var searcher = new Worker('searcher.js');
   function search(query) {
     searcher.postMessage(query);
   }

   // SYMBOL SELECTION UI
   function select(newSymbol) {
     symbol = newSymbol;
     ticker.postMessage(symbol);
   }
  &lt;/script>
 &lt;/head>
 &lt;body>
  &lt;p>&lt;output id="symbol">&lt;/output> &lt;output id="value">&lt;/output>&lt;/p>
  &lt;script>
   ticker.onmessage = function (event) {
     var data = event.message.split(' ');
     document.getElementById('symbol').textContent = data[0];
     document.getElementById('value').textContent = data[1];
   };
   ticker.postMessage(symbol);
  &lt;/script>
  &lt;p>&lt;label>Search: &lt;input type="text" oninput="search(this.value)">&lt;/label>&lt;/p>
  &lt;ul id="results">&lt;/ul>
  &lt;script>
   searcher.onmessage = function (event) {
     var data = event.message.split(' ');
     var results = document.getElementById('results');
     while (results.hasChildNodes()) // clear previous results
       results.removeChild(results.firstChild);
     for (var i = 0; i &lt; data.length; i += 1) {
       // add a list item with a button for each result
       var li = document.createElement('li');
       var button = document.createElement('button');
       button.value = data[i];
       button.type = 'button';
       button.onclick = function () { select(this.value); };
       button.textContent = data[i];
       li.appendChild(button);
       results.appendChild(li);
     }
   };
  &lt;/script>
  &lt;p>(The data in this example is not real. Try searching for "Google" or "Apple".)&lt;/p>
 &lt;/body>
&lt;/html></pre>

  <p class="no-ja-translation">The two workers use a common library for performing the actual network
   calls. This library is as follows:

  <pre class="no-ja-translation">function get(url) {
  try {
    var xhr = new XMLHttpRequest();
    xhr.open('GET', url, false);
    xhr.send();
    return xhr.responseText;
  } catch (e) {
    return ''; // turn all errors into empty results
  }
}</pre>

  <p class="no-ja-translation">The stock updater worker is as follows:

  <pre class="no-ja-translation">importScripts('io.js');
var timer;
var symbol;
function update() {
  postMessage(symbol + ' ' + get('stock.cgi?' + symbol));
  timer = setTimeout(update, 10000);
}
onmessage = function (event) {
  if (timer)
    clearTimeout(timer);
  symbol = event.message;
  update();
};</pre>

  <p class="no-ja-translation">The search query worker is as follows:

  <pre class="no-ja-translation">importScripts('io.js');
onmessage = function (event) {
  postMessage(get('search.cgi?' + event.message));
};</pre>

  <p class="has-ja-translation"><span class=en-original lang=en><a href="http://www.whatwg.org/demos/workers/stocks/page.html">View this
   example online</a>.

  </span><span class=ja-translation lang=ja><a href="http://www.whatwg.org/demos/workers/stocks/page.html">この例をオンラインで見る</a>。</span><h4 id=shared class="no-ja-translation"><span class=secno>1.1.4 </span>Shared workers</h4>

  <p class="has-ja-translation"><span class=en-original lang=en><em>This section is non-normative.</em>

  </span><span class=ja-translation lang=ja><em>この節は規定の一部ではありません。</em></span><p class="no-ja-translation">In this example, multiple windows (viewers) can be opened that are all
   viewing the same map. All the windows share the same map information, with
   a single worker coordinating all the viewers. Each viewer can move around
   idependently, but if they set any data on the map, all the viewers are
   updated.

  <p class="no-ja-translation">The main page isn't interesting, it merely provides a way to open the
   viewers:

  <pre class="no-ja-translation">&lt;!DOCTYPE HTML>
&lt;html>
 &lt;head>
  &lt;title>Workers example: Multiviewer&lt;/title>
  &lt;script>
   function openViewer() {
     window.open('viewer.html');
   }
  &lt;/script>
 &lt;/head>
 &lt;body>
  &lt;p>&lt;button type=button onclick="openViewer()">Open a new
  viewer&lt;/button>&lt;/p>
  &lt;p>Each viewer opens in a new window. You can have as many viewers
  as you like, they all view the same data.&lt;/p>
 &lt;/body>
&lt;/html></pre>

  <p class="no-ja-translation">The viewer is more involved:

  <pre class="no-ja-translation">&lt;!DOCTYPE HTML>
&lt;html>
 &lt;head>
  &lt;title>Workers example: Multiviewer viewer&lt;/title>
  &lt;script>
   var worker = new SharedWorker('worker.js', 'core');

   // CONFIGURATION
   function configure(event) {
     if (event.message.substr(0, 4) != 'cfg ') return;
     var name = event.message.substr(4).split(' ', 1);
     // update display to mention our name is name
     document.getElementsByTagName('h1')[0].textContent += ' ' + name;
     // no longer need this listener
     worker.port.removeEventListener('message', configure, false);
   }
   worker.port.addEventListener('message', configure, false);

   // MAP
   function paintMap(event) {
     if (event.message.substr(0, 4) != 'map ') return;
     var data = event.message.substr(4).split(',');
     // display tiles data[0] .. data[8]
     var canvas = document.getElementById('map');
     var context = canvas.getContext('2d');
     for (var y = 0; y &lt; 3; y += 1) {
       for (var x = 0; x &lt; 3; x += 1) {
         var tile = data[y * 3 + x];
         if (tile == '0')
           context.fillStyle = 'green';
         else 
           context.fillStyle = 'maroon';
         fillRect(x * 50, y * 50, 50, 50);
       }
     }
   }
   worker.port.addEventListener('message', paintMap, false);

   // PUBLIC CHAT
   function updatePublicChat(event) {
     if (event.message.substr(0, 4) != 'txt ') return;
     var name = event.message.substr(4).split(' ', 1);
     var message = event.message.substr(4 + length(name) + 1);
     // display "&lt;name> message" in public chat
     var dialog = document.getElementById('public');
     var dt = document.createElement('dt');
     dt.textContent = name;
     dialog.appendChild(dt);
     var dd = document.createElement('dd');
     dd.textContent = message;
     dialog.appendChild(dd);
   }
   worker.port.addEventListener('message', updatePublicChat, false);

   // PRIVATE CHAT
   function startPrivateChat(event) {
     if (event.message.substr(0, 4) != 'msg ') return;
     var name = event.message.substr(4).split(' ', 1);
     var port = event.port;
     // display a private chat UI
     var ul = document.getElementById('private');
     var li = document.createElement('li');
     var h3 = document.createElement('h3');
     h3.textContent = 'Private chat with ' + name;
     li.appendChild(h3);
     var dialog = document.createElement('dialog');
     var addMessage = function(name, message) {
       var dt = document.createElement('dt');
       dt.textContent = name;
       dialog.appendChild(dt);
       var dd = document.createElement('dd');
       dd.textContent = message;
       dialog.appendChild(dd);
     };
     port.onmessage = function (event) {
       addMessage(name, event.message);
     };
     li.appendChild(dialog);
     var form = document.createElement('form');
     var p = document.createElement('p');
     var input = document.createElement('input');
     input.size = 50;
     p.appendChild(input);
     p.appendChild(document.createTextNode(' '));
     var button = document.createElement('button');
     button.textContent = 'Post';
     p.appendChild(button);
     form.onsubmit = function () {
       port.postMessage(input.value);
       addMessage('me', input.value);
       input.value = '';
       return false;
     };
     form.appendChild(p);
     li.appendChild(form);
   }
   worker.port.addEventListener('message', startPrivateChat, false);
  &lt;/script>
 &lt;/head>
 &lt;body>
  &lt;h1>Viewer&lt;/h1>
  &lt;h2>Map&lt;/h2>
  &lt;p>&lt;canvas id="map" height=150 width=150>&lt;/canvas>&lt;/p>
  &lt;p>
   &lt;button type=button onclick="worker.port.postMessage('mov left')">Left&lt;/button>
   &lt;button type=button onclick="worker.port.postMessage('mov up')">Up&lt;/button>
   &lt;button type=button onclick="worker.port.postMessage('mov down')">Down&lt;/button>
   &lt;button type=button onclick="worker.port.postMessage('mov right')">Right&lt;/button>
   &lt;button type=button onclick="worker.port.postMessage('set 0')">Set 0&lt;/button>
   &lt;button type=button onclick="worker.port.postMessage('set 1')">Set 1&lt;/button>
  &lt;/p>
  &lt;h2>Public Chat&lt;/h2>
  &lt;dialog id="public">&lt;/dialog>
  &lt;form onsubmit="worker.port.postMessage('txt ' + message.value); message.value = ''; return false;">
   &lt;p>
    &lt;input type="text" name="message" size="50">
    &lt;button>Post&lt;/button>
   &lt;/p>
  &lt;/form>
  &lt;h2>Private Chat&lt;/h2>
  &lt;ul id="private">&lt;/ul>
 &lt;/body>
&lt;/html>
</pre>

  <p class="no-ja-translation">There are several key things worth noting about the way the viewer is
   written.

  <p class="no-ja-translation"><strong>Multiple listeners</strong>. Instead of a single message
   processing function, the code here attaches multiple event listeners, each
   one performing a quick check to see if it is relevant for the message. In
   this example it doesn't make much difference, but if multiple authors
   wanted to collaborate using a single port to communicate with a worker, it
   would allow for independent code instead of changes having to all be made
   to a single event handling function.

  <p class="no-ja-translation">Registering event listeners in this way also allows you to unregister
   specific listeners when you are done with them, as is done with the <code
   title="">configure()</code> method in this example.

  <p class="no-ja-translation">Finally, the worker:

  <pre class="no-ja-translation">
var nextName = 0;
function getNextName() {
  // this could use more friendly names
  // but for now just return a number
  return nextName++;
}

var map = [
 [0, 0, 0, 0, 0, 0, 0],
 [1, 1, 0, 1, 0, 1, 1],
 [0, 1, 0, 1, 0, 0, 0],
 [0, 1, 0, 1, 0, 1, 1],
 [0, 0, 0, 1, 0, 0, 0],
 [1, 0, 0, 1, 1, 1, 1],
 [1, 1, 0, 1, 1, 0, 1],
];

function wrapX(x) {
  if (x &lt; 0) return wrapX(x + map[0].length);
  if (x >= map[0].length) return wrapX(x - map[0].length);
  return x;
}

function wrapY(y) {
  if (y &lt; 0) return wrapY(y + map.length);
  if (y >= map[0].length) return wrapY(y - map.length);
  return y;
}

function sendMapData(callback) {
  var data = '';
  for (var y = viewer.y-1; y &lt;= viewer.y+1; y += 1) {
    for (var x = viewer.x-1; x &lt;= viewer.x+1; x += 1) {
      if (data != '')
        data += ',';
      data += map[y][x];
    }
  }
  callback('map ' + data);
}

var viewers = {};
onconnect = function (event) {
  event.port._name = getNextName();
  event.port._data = { port: event.port, x: 0, y: 0, };
  viewers[event.port._name] = event.port._data;
  event.port.postMessage('cfg ' + name);
  event.port.onmessage = getMessage;
  sendMapData(event.port.postMessage);
};

function getMessage(event) {
  switch (event.message.substr(0, 4)) {
    case 'mov ':
      var direction = event.message.substr(4);
      var dx = 0;
      var dy = 0;
      switch (direction) {
        case 'up': dy = -1; break;
        case 'down': dy = 1; break;
        case 'left': dx = -1; break;
        case 'right': dx = 1; break;
      }
      event.target._data.x = wrapX(event.target._data.x + dx);
      event.target._data.y = wrapY(event.target._data.y + dy);
      sendMapData(event.target.postMessage);
      break;
    case 'set ':
      var value = event.message.substr(4);
      map[event.target._data.y][event.target._data.x] = value;
      for (var viewer in viewers)
        sendMapData(viewers[viewer].port.postMessage);
      break;
    case 'txt ':
      var name = event.target._name;
      var message = event.message.substr(4);
      for (var viewer in viewers)
        viewers[viewer].port.postMessage('txt ' + name + ' ' + message);
      break;
    case 'msg ':
      var party1 = event._data;
      var party2 = viewers[event.message.substr(4).split(' ', 1)];
      if (party2) {
        var channel = new MessageChannel();
        party1.port.postMessage('msg ' + party2.name, channel.port1);
        party2.port.postMessage('msg ' + party1.name, channel.port2);
      }
      break;
  }
}</pre>

  <p class="no-ja-translation"><strong>Connecting to multiple pages</strong>. The script uses the <code
   title=handler-SharedWorkerGlobalScope-onconnect><a
   href="#onconnect">onconnect</a></code> event listener to listen for
   multiple connections.

  <p class="no-ja-translation"><strong>Direct channels</strong>. When the worker receives a "msg"
   message from one viewer naming another viewer, it sets up a direct
   connection between the two, so that the two viewers can communicate
   directly without the worker having to proxy all the messages.

  <p class="has-ja-translation"><span class=en-original lang=en><a href="http://www.whatwg.org/demos/workers/multiviewer/page.html">View
   this example online</a>.

  </span><span class=ja-translation lang=ja><a href="http://www.whatwg.org/demos/workers/multiviewer/page.html">この例をオンラインで見る</a>。</span><h4 id=delegation class="no-ja-translation"><span class=secno>1.1.5 </span>Delegation</h4>

  <p class="has-ja-translation"><span class=en-original lang=en><em>This section is non-normative.</em>

  </span><span class=ja-translation lang=ja><em>この節は規定の一部ではありません。</em></span><p class="no-ja-translation">With multicore CPUs becoming prevalent, one way to obtain better
   performance is to split computationally expensive tasks amongst multiple
   workers. In this example, a computationally expensive task that is to be
   performed for every number from 1 to 10,000,000 is farmed out to ten
   subworkers.

  <p class="no-ja-translation">The main page is as follows, it just reports the result:

  <pre class="no-ja-translation">&lt;!DOCTYPE HTML>
&lt;html>
 &lt;head>
  &lt;title>Worker example: One-core computation&lt;/title>
 &lt;/head>
 &lt;body>
  &lt;p>The highest prime number discovered so far is: &lt;output id="result">&lt;/output>&lt;/p>
  &lt;script>
   var worker = new Worker('worker.js');
   worker.onmessage = function (event) {
     document.getElementById('result').textContent = event.message;
   };
  &lt;/script>
 &lt;/body>
&lt;/html></pre>

  <p class="has-ja-translation"><span class=en-original lang=en>The worker itself is as follows:

  </span><span class=ja-translation lang=ja>労働者自体は次の通りです。</span><pre class="no-ja-translation">// settings
var num_workers = 10;
var items_per_worker = 1000000;

// start the workers
var result = 0;
var pending_workers = num_workers;
for (var i = 0; i &lt; num_workers; i += 1) {
  var worker = new Worker('core.js');
  worker.postMessage(i * items_per_worker);
  worker.postMessage((i+1) * items_per_worker);
  worker.onmessage = storeResult;
}

// handle the results
function storeResult(event) {
  result += 1*event.message;
  pending_workers -= 1;
  if (pending_workers &lt;= 0)
    postMessage(result); // finished!
}</pre>

  <p class="no-ja-translation">It consists of a loop to start the subworkers, and then a handler that
   waits for all the subworkers to respond.

  <p class="no-ja-translation">The subworkers are implemented as follows:

  <pre class="no-ja-translation">var start;
onmessage = getStart;
function getStart(event) {
  start = 1*event.message;
  onmessage = getEnd;
}

var end;
function getEnd(event) {
  end = 1*event.message;
  onmessage = null;
  do();
}

function do() {
  var result = 0;
  for (var i = start; i &lt; end; i += 1) {
    // perform some complex calculation here
    result += 1;
  }
  postMessage(result);
  close();
}</pre>

  <p class="no-ja-translation">They receive two numbers in two events, perform the computation for the
   range of numbers thus specified, and then report the result back to the
   parent.

  <p class="has-ja-translation"><span class=en-original lang=en><a href="http://www.whatwg.org/demos/workers/multicore/page.html">View
   this example online</a>.

  </span><span class=ja-translation lang=ja><a href="http://www.whatwg.org/demos/workers/multicore/page.html">この例をオンラインで見る</a>。</span><h4 id=providing class="no-ja-translation"><span class=secno>1.1.6 </span>Providing libraries</h4>

  <p class="has-ja-translation"><span class=en-original lang=en><em>This section is non-normative.</em>

  </span><span class=ja-translation lang=ja><em>この節は規定の一部ではありません。</em></span><p class="no-ja-translation">Suppose that a cryptography library is made available that provides
   three tasks:

  <dl>
   <dt class="no-ja-translation">Generate a public/private key pair

   <dd class="no-ja-translation">Takes a port, on which it will send two messages, first the public key
    and then the private key.

   <dt class="no-ja-translation">Given a plaintext and a public key, return the corresponding
    cyphertext

   <dd class="no-ja-translation">Takes a port, to which any number of messages can be sent, the first
    giving the public key, and the remainder giving the plaintext, each of
    which is encrypted and then sent on that same channel as the cyphertext.
    The user can close the port when it is done encrypting content.

   <dt class="no-ja-translation">Given a cyphertext and a private key, return the corresponding
    plaintext

   <dd class="no-ja-translation">Takes a port, to which any number of messages can be sent, the first
    giving the private key, and the remainder giving the cyphertext, each of
    which is decrypted and then sent on that same channel as the plaintext.
    The user can close the port when it is done decrypting content.
  </dl>

  <p class="no-ja-translation">The library itself is as follows:

  <pre class="no-ja-translation">function handleMessage(e) {
  if (e.message == "genkeys")
    genkeys(e.port);
  else if (e.message == "encrypt")
    encrypt(e.port);
  else if (e.message == "decrypt")
    decrypt(e.port);
}

function genkeys(p) {
  var keys = _generateKeyPair();
  p.postMessage(keys[0]);
  p.postMessage(keys[1]);
}

function encrypt(p) {
  var key, state = 0;
  p.onmessage = function (e) {
    if (state == 0) {
      key = e.message;
      state = 1;
    } else {
      p.postMessage(_encrypt(key, e.message));
    }
  };
}

function decrypt(p) {
  var key, state = 0;
  p.onmessage = function (e) {
    if (state == 0) {
      key = e.message;
      state = 1;
    } else {
      p.postMessage(_decrypt(key, e.message));
    }
  };
}

// support being used as a shared worker as well as a dedicated worker
if (this.onmessage) // dedicated worker
  onmessage = handleMessage;
else // shared worker
  onconnect = function (e) { e.port.onmessage = handleMessage; }


// the "crypto" functions:

function _generateKeyPair() {
  return [Math.random(), Math.random()];
}

function _encrypt(k, s) {
  return 'encrypted-' + k + ' ' + s;
}

function _decrypt(k, s) {
  return s.substr(s.indexOf(' ')+1);
}</pre>

  <p class="no-ja-translation">Note that the crypto functions here are just stubs and don't do real
   cryptography.

  <p class="no-ja-translation">This library could be used as follows:

  <pre class="no-ja-translation">&lt;!DOCTYPE HTML>
&lt;html>
 &lt;head>
  &lt;title>Worker example: Crypto library&lt;/title>
  &lt;script>
   var crytoLib = new Worker('libcrypto-v1.js'); // or could use 'libcrypto-v2.js'
   function getKeys() {
     var state = 0;
     cryptoLib.startConversation("genkeys").onmessage = function (e) {
       if (state == 0)
         document.getElementById('public').value = e.message;
       else if (state == 1)
         document.getElementById('private').value = e.message;
       state += 1;
     };
   }
   function enc() {
     var port = cryptoLib.startConversation("encrypt");
     port.postMessage(document.getElementById('public').value);
     port.postMessage(document.getElementById('input').value);
     port.onmessage = function (e) {
       document.getElementById('input').value = e.message;
       port.close();
     };
   }
   function dec() {
     var port = cryptoLib.startConversation("decrypt");
     port.postMessage(document.getElementById('private').value);
     port.postMessage(document.getElementById('input').value);
     port.onmessage = function (e) {
       document.getElementById('input').value = e.message;
       port.close();
     };
   }
  &lt;/script>
  &lt;style>
   textarea { display: block; }
  &lt;/style>
 &lt;/head>
 &lt;body onload="getKeys()">
  &lt;fieldset>
   &lt;legend>Keys&lt;/legend>
   &lt;p>&lt;label>Public Key: &lt;textarea id="public">&lt;/textarea>&lt;/label>&lt;/p>
   &lt;p>&lt;label>Private Key: &lt;textarea id="private">&lt;/textarea>&lt;/label>&lt;/p>
  &lt;/fieldset>
  &lt;p>&lt;label>Input: &lt;textarea id="input">&lt;/textarea>&lt;/label>&lt;/p>
  &lt;p>&lt;button onclick="enc()">Encrypt&lt;/button> &lt;button onclick="dec()">Decrypt&lt;/button>&lt;/p>
 &lt;/body>
&lt;/html></pre>

  <p class="no-ja-translation">A later version of the API, though, might want to offload all the crypto
   work onto subworkers. This could be done as follows:

  <pre class="no-ja-translation">function handleMessage(e) {
  if (e.message == "genkeys")
    genkeys(e.port);
  else if (e.message == "encrypt")
    encrypt(e.port);
  else if (e.message == "decrypt")
    decrypt(e.port);
}

function genkeys(p) {
  var generator = new Worker('libcrypto-v2-generator.js');
  generator.postMessage('', p);
}

function encrypt(p) {
  p.onmessage = function (e) {
    var key = e.message;
    var encryptor = new Worker('libcrypto-v2-encryptor.js');
    encryptor.postMessage(key, p);
  };
}

function encrypt(p) {
  p.onmessage = function (e) {
    var key = e.message;
    var decryptor = new Worker('libcrypto-v2-decryptor.js');
    decryptor.postMessage(key, p);
  };
}

// support being used as a shared worker as well as a dedicated worker
if (this.onmessage) // dedicated worker
  onmessage = handleMessage;
else // shared worker
  onconnect = function (e) { e.port.onmessage = handleMessage; }
</pre>

  <p class="no-ja-translation">The little subworkers would then be as follows.

  <p class="no-ja-translation">For generating key pairs:

  <pre class="no-ja-translation">onmessage = function (e) {
  var k = _generateKeyPair();
  e.port.postMessage(k[0]);
  e.port.postMessage(k[1]);
  close();
}

function _generateKeyPair() {
  return [Math.random(), Math.random()];
}</pre>

  <p class="no-ja-translation">For encrypting:

  <pre class="no-ja-translation">onmessage = function (e) {
  var key = e.message;
  e.port.onmessage = function (e) {
    var s = e.message;
    postMessage(_encrypt(key, s));
  }
  e.port.onclose = function (e) {
    close();
  }
}

function _encrypt(k, s) {
  return 'encrypted-' + k + ' ' + s;
}</pre>

  <p class="no-ja-translation">For decrypting:

  <pre class="no-ja-translation">onmessage = function (e) {
  var key = e.message;
  e.port.onmessage = function (e) {
    var s = e.message;
    postMessage(_decrypt(key, s));
  }
  e.port.onclose = function (e) {
    close();
  }
}

function _decrypt(k, s) {
  return s.substr(s.indexOf(' ')+1);
}</pre>

  <p class="no-ja-translation">Notice how the users of the API don't have to even know that this is
   happening &mdash; the API hasn't changed; the library can delegate to
   subworkers without changing its API, even though it is accepting data
   using message channels.

  <p class="has-ja-translation"><span class=en-original lang=en><a href="http://www.whatwg.org/demos/workers/crypto/page.html">View this
   example online</a>.

  </span><span class=ja-translation lang=ja><a href="http://www.whatwg.org/demos/workers/crypto/page.html">この例をオンラインで見る</a>。</span><h3 id=conformance class="has-ja-translation"><span class=en-original lang=en><span class=secno>1.2 </span>Conformance requirements</span><span class=ja-translation lang=ja><span class=secno>1.2 </span>適合性要件</span></h3>

  <p class="has-ja-translation"><span class=en-original lang=en>All diagrams, examples, and notes in this specification are
   non-normative, as are all sections explicitly marked non-normative.
   Everything else in this specification is normative.

  </span><span class=ja-translation lang=ja>この仕様書のすべての図、例示、注意書き、ならびに規定の一部ではないと明記したすべての節は、
規定の一部ではありません。
この仕様書のそれ以外の部分はすべて規定の一部です。</span><p class="no-ja-translation">The key words "MUST", "MUST NOT", "REQUIRED", <!--"SHALL", "SHALL
  NOT",-->
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in the
   normative parts of this document are to be interpreted as described in
   RFC2119. For readability, these words do not appear in all uppercase
   letters in this specification. <a href="#refsRFC2119">[RFC2119]</a></p>
  <!-- XXX but they should be
  marked up -->

  <p class="has-ja-translation"><span class=en-original lang=en>Requirements phrased in the imperative as part of algorithms (such as
   "strip any leading space characters" or "return false and abort these
   steps") are to be interpreted with the meaning of the key word ("must",
   "should", "may", etc) used in introducing the algorithm.

  </span><span class=ja-translation lang=ja>算法の一部として<ins class=ja-note>動作の指示の形で (原文では</ins>命令形で<ins class=ja-note>) </ins>記述された要件
(例えば「先頭の間隔文字をすべて除去します」や「偽を返し、これらの段階を停止します」)
は、算法を紹介するに当たって使われたキーワード (<em class=rfc2119 title="MUST">しなければなりません</em>、
<em class=rfc2119 title="SHOULD">するべきです</em>、<em class=rfc2119 title="MAY">して構いません</em>など) の意味により解釈します。</span><p class="has-ja-translation"><span class=en-original lang=en>Some conformance requirements are phrased as requirements on attributes,
   methods or objects. Such requirements are to be interpreted as
   requirements on user agents.

  </span><span class=ja-translation lang=ja>いくつかの適合性要件は属性やメソッドやオブジェクトの要件として説明されています。
そのような要件は、利用者エージェントに関する要件として解釈します。</span><p class="has-ja-translation"><span class=en-original lang=en>Conformance requirements phrased as algorithms or specific steps may be
   implemented in any manner, so long as the end result is equivalent. (In
   particular, the algorithms defined in this specification are intended to
   be easy to follow, and not intended to be performant.)

  </span><span class=ja-translation lang=ja>算法や特定の段階として説明されている適合性要件は、
最終的な結果が等価である限り、任意の方法で実装して<em class=rfc2119 title="MAY">構いません</em>。
(特に、この仕様書で定義されている算法は追うのを簡単にしており、
高性能であることを目指してはいません。)</span><p class="has-ja-translation"><span class=en-original lang=en>The only conformance class defined by this specification is user agents.

  </span><span class=ja-translation lang=ja>この仕様書で定義する唯一の適合性の級は利用者エージェントです。</span><p class="has-ja-translation"><span class=en-original lang=en>User agents may impose implementation-specific limits on otherwise
   unconstrained inputs, e.g. to prevent denial of service attacks, to guard
   against running out of memory, or to work around platform-specific
   limitations.

  </span><span class=ja-translation lang=ja>利用者エージェントは、サービス拒否攻撃を防ぐため、
記憶容量を使い尽くすことを防ぐため、
あるいは環境特有の制限に対応するためなどの目的で、
別段の制約のない入力に対して実装特有の制限を設けて<em class=rfc2119 title="MAY">構いません</em>。</span><h4 id=dependencies class="has-ja-translation"><span class=en-original lang=en><span class=secno>1.2.1 </span>Dependencies</span><span class=ja-translation lang=ja><span class=secno>1.2.1 </span>依存性</span></h4>

  <p class="has-ja-translation"><span class=en-original lang=en>This specification relies on several other underlying specifications.

  </span><span class=ja-translation lang=ja>この仕様書は、他のいくつかの下位の仕様書に依存しています。</span><dl>
   <dt class="no-ja-translation">HTML5

   <dd>
    <p class="no-ja-translation">Many fundamental concepts from HTML5 are used by this specification.
     <a href="#refsHTML5">[HTML5]</a></p>

   <dt class="no-ja-translation">ECMAScript

   <dd>
    <p class="no-ja-translation">This specification is intended to be used with JavaScript as the
     scripting language. <a href="#refsJS">[JS]</a></p>

   <dt class="no-ja-translation">WebIDL

   <dd>
    <p class="no-ja-translation">The IDL blocks in this specification use the semantics of the WebIDL
     specification. <a href="#refsWebIDL">[WebIDL]</a></p>
  </dl>

  <h3 id=terminology class="has-ja-translation"><span class=en-original lang=en><span class=secno>1.3 </span>Terminology</span><span class=ja-translation lang=ja><span class=secno>1.3 </span>用語</span></h3>

  <p class="has-ja-translation"><span class=en-original lang=en>For simplicity, terms such as <em>shown</em>, <em>displayed</em>, and
   <em>visible</em> might sometimes be used when referring to the way a
   document is rendered to the user. These terms are not meant to imply a
   visual medium; they must be considered to apply to other media in
   equivalent ways.

  </span><span class=ja-translation lang=ja>簡単のため、文書が利用者に対してレンダリングされる方法に言及する時に<em>示す</em>、
<em>表示する</em>、<em>可視</em>などの用語を使うことがあります。
このような用語は特に視覚媒体を暗示しているわけではありません。
他の媒体であってもこれらの用語が等価な方法で適用されるものと考えなければ<em class=rfc2119 title="MUST">なりません</em>。</span><p class="has-ja-translation"><span class=en-original lang=en>The construction "a <code title="">Foo</code> object", where <code
   title="">Foo</code> is actually an interface, is sometimes used instead of
   the more accurate "an object implementing the interface <code
   title="">Foo</code>".

  </span><span class=ja-translation lang=ja>「<code title="">Foo</code> オブジェクト」という構文 (<code title="">Foo</code>
は実際には界面) を時々使いますが、より正確な「界面 <code title="">Foo</code>
を実装しているオブジェクト」の代わりに用いています。</span><p class="no-ja-translation">The term DOM is used to refer to the API set made available to scripts
   in Web applications, and does not necessarily imply the existence of an
   actual <code>Document</code> object or of any other <code>Node</code>
   objects as defined in the DOM Core specifications. <a
   href="#refsDOM3CORE">[DOM3CORE]</a>

  <p class="has-ja-translation"><span class=en-original lang=en>A DOM attribute is said to be <em>getting</em> when its value is being
   retrieved (e.g. by author script), and is said to be <em>setting</em> when
   a new value is assigned to it.

  </span><span class=ja-translation lang=ja>DOM 属性は、その値が (例えば著者のスクリプトにより) 取り出される時<em>取得される</em>といい、
新しい値がその属性に割り当てられる時<em>設定される</em>といいます。</span><p class="has-ja-translation"><span class=en-original lang=en>If a DOM object is said to be <dfn id="en-live">live</dfn>, then that means
   that any attributes returning that object must always return the same
   object (not a new object each time), and the attributes and methods on
   that object must operate on the actual underlying data, not a snapshot of
   the data.

  </span><span class=ja-translation lang=ja>DOM オブジェクトが<dfn id=live>生きている</dfn>という場合、
そのオブジェクトを返す属性は常に同じオブジェクトを返さなければ<em class=rfc2119 title="MUST">ならない</em>
(毎回新しいオブジェクトを返すのではなく) 上に、
そのオブジェクトの属性やメソッドがそのオブジェクトの裏にある実際のデータのスナップ写真ではなく、
データそのものに対して操作されなければ<em class=rfc2119 title="MUST">ならない</em>ことを意味します。</span><h2 id=infrastructure class="has-ja-translation"><span class=en-original lang=en><span class=secno>2. </span>Infrastructure</span><span class=ja-translation lang=ja><span class=secno>2. </span>基盤</span></h2>

  <p class="no-ja-translation">There are two kinds of workers; dedicated workers, and shared workers.
   Dedicated workers, once created, and are linked to their creator; but
   message ports can be used to communicate from a dedicated worker to
   multple other browsing contexts or workers. Shared workers, on the other
   hand, are named, and once created any script running in the same
   <span>origin</span> can obtain a reference to that worker and communicate
   with it.

  <h3 id=the-global class="no-ja-translation"><span class=secno>2.1 </span>The global scope</h3>

  <p class="no-ja-translation">The global scope is the "inside" of a worker.

  <h4 id=the-workerglobalscope class="has-ja-translation"><span class=en-original lang=en><span class=secno>2.1.1 </span>The <code><a
   href="#workerglobalscope">WorkerGlobalScope</a></code> abstract interface</span><span class=ja-translation lang=ja><span class=secno>2.1.1 </span><code><a href="#workerglobalscope">WorkerGlobalScope</a></code> abstract 界面</span></h4>

  <pre
   class="idl no-ja-translation">[NoInterfaceObject] interface <dfn id=workerglobalscope>WorkerGlobalScope</dfn> {
  readonly attribute <a href="#workerglobalscope">WorkerGlobalScope</a> <a href="#self" title=dom-WorkerGlobalScope-self>self</a>;
  readonly attribute <a href="#workerlocation">WorkerLocation</a> <a href="#location" title=dom-WorkerGlobalScope-location>location</a>;
  // also implements everything on <a href="#workerutils">WorkerUtils</a>

  void <a href="#close" title=dom-WorkerGlobalScope-close>close</a>();
           attribute <span>EventListener</span> <a href="#onclose" title=handler-WorkerGlobalScope-onclose>onclose</a>;
};</pre>

  <p class="no-ja-translation">Objects implementing the <code><a
   href="#workerglobalscope">WorkerGlobalScope</a></code> interface it must
   also implement the <code>EventTarget</code> interface.

  <p class="no-ja-translation">The <dfn id=self
   title=dom-WorkerGlobalScope-self><code>self</code></dfn> attribute must
   return the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
   object itself.

  <p class="no-ja-translation">The <dfn id=location
   title=dom-WorkerGlobalScope-location><code>location</code></dfn> attribute
   must return the <code><a href="#workerlocation">WorkerLocation</a></code>
   object created for the <code><a
   href="#workerglobalscope">WorkerGlobalScope</a></code> object when the
   worker was created. It represents the <span>absolute URL</span> of the
   script that was used to initialize the worker.

  <hr>

  <p class="no-ja-translation">When a script invokes the <dfn id=close
   title=dom-WorkerGlobalScope-close><code>close()</code></dfn> method on a
   <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object,
   the user agent must run the following steps:

  <ol>
   <li>
    <p class="no-ja-translation">Create an <code>Event</code> object with the event name <code
     title=event-close>close</code>, which does not bubble and is not
     cancelable, and add it to the <code><a
     href="#workerglobalscope">WorkerGlobalScope</a></code> object's <a
     href="#queue">queue of events</a>, targetted at the <code><a
     href="#workerglobalscope">WorkerGlobalScope</a></code> object itself.

   <li>
    <p class="no-ja-translation">Set the worker's <code><a
     href="#workerglobalscope">WorkerGlobalScope</a></code> object's <a
     href="#closing" title=dom-WorkerGlobalScope-closing>closing</a> flag to
     true.

   <li>
    <p class="no-ja-translation">For each <code>MessagePort</code> object that is entangled with
     another port and that has one (but only one) port whose owner is the
     <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object
     on which the method was invoked (this would include, for instance, the
     implicit port in used for dedicated workers), run the following
     substeps:</p>

    <ol>
     <li>
      <p class="has-ja-translation"><span class=en-original lang=en>Unentangle the two ports.

     </span><span class=ja-translation lang=ja>2つのポートをほどきます。</span><li>
      <p class="no-ja-translation">At the next available opportunity, after any scripts have finished
       executing<!-- XXX queue -->, <span>fire a simple event</span> called
       <code title=event-close>close</code> at the other port (the one whose
       owner is not the <code><a
       href="#workerglobalscope">WorkerGlobalScope</a></code> object on which
       the <code title=dom-WorkerGlobalScope-close><a
       href="#close">close()</a></code> method was called).
    </ol>
  </ol>

  <p class="no-ja-translation">The following are the <span>event handler DOM attributes</span> that
   must be supported by objects implementing the <code><a
   href="#workerglobalscope">WorkerGlobalScope</a></code> interface:

  <dl>
   <dt class="no-ja-translation"><dfn id=onclose
    title=handler-WorkerGlobalScope-onclose><code>onclose</code></dfn>

   <dd>
    <p class="has-ja-translation"><span class=en-original lang=en>Must be invoked whenever a <code title=event-close>close</code> event
     is targeted at or bubbles through the <code><a
     href="#workerglobalscope">WorkerGlobalScope</a></code> object.
  </span><span class=ja-translation lang=ja><code title=event-close>close</code> 事象が当該 <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> オブジェクトを対象としているか、泡立って当該オブジェクトを通過する時に、
呼び出されなければなりません。</span></dl>

  <h4 id=dedicated class="no-ja-translation"><span class=secno>2.1.2 </span>Dedicated workers and the
   <code><a
   href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
   interface</h4>

  <pre
   class="idl no-ja-translation">[NoInterfaceObject] interface <dfn id=dedicatedworkerglobalscope>DedicatedWorkerGlobalScope</dfn> : <a href="#workerglobalscope">WorkerGlobalScope</a> {
  void <a href="#postmessage" title=dom-DedicatedWorkerGlobalScope-postMessage>postMessage</a>(in DOMString message);
  void <a href="#postmessage" title=dom-DedicatedWorkerGlobalScope-postMessage>postMessage</a>(in DOMString message, in <span>MessagePort</span> messagePort);
  <span>MessagePort</span> <a href="#startconversation" title=dom-DedicatedWorkerGlobalScope-startConversation>startConversation</a>(in DOMString message);
           attribute <span>EventListener</span> <a href="#onmessage" title=handler-DedicatedWorkerGlobalScope-onmessage>onmessage</a>;
};</pre>

  <p class="no-ja-translation"><code><a
   href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
   objects act as if they had an implicit <code>MessagePort</code> associated
   with them. This port is part of a channel that is set up when the worker
   is created, but it is not exposed. This object must never be garbage
   collected before the <code><a
   href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
   object.

  <p class="no-ja-translation">All messages received by that port must immediately be retargetted at
   the <code><a
   href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
   object.

  <p class="no-ja-translation">The <dfn id=postmessage
   title=dom-DedicatedWorkerGlobalScope-postMessage><code>postMessage()</code></dfn>
   and <dfn id=startconversation
   title=dom-DedicatedWorkerGlobalScope-startConversation><code>startConversation()</code></dfn>
   methods on <code><a
   href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
   objects must act as if, when invoked, they immediately invoked the method
   of the same name on the port, with the same arguments, and returned the
   same return value.

  <p class="no-ja-translation">The following are the <span>event handler DOM attributes</span> that
   must be supported by objects implementing the <code><a
   href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
   interface:

  <dl>
   <dt class="no-ja-translation"><dfn id=onmessage
    title=handler-DedicatedWorkerGlobalScope-onmessage><code>onmessage</code></dfn>

   <dd>
    <p class="has-ja-translation"><span class=en-original lang=en>Must be invoked whenever a <code
     title=event-DedicatedWorkerGlobalScope-message>message</code> event is
     targeted at or bubbles through the <code><a
     href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
     object.
  </span><span class=ja-translation lang=ja><code title=event-DedicatedWorkerGlobalScope-message>message</code> 事象が当該 <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> オブジェクトを対象としているか、泡立って当該オブジェクトを通過する時に、
呼び出されなければなりません。</span></dl>

  <h4 id=shared0 class="no-ja-translation"><span class=secno>2.1.3 </span>Shared workers and the
   <code><a
   href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
   inteface</h4>

  <pre
   class="idl no-ja-translation">[NoInterfaceObject] interface <dfn id=sharedworkerglobalscope>SharedWorkerGlobalScope</dfn> : <a href="#workerglobalscope">WorkerGlobalScope</a> {
  readonly attribute DOMString <a href="#name" title=dom-SharedWorkerGlobalScope-name>name</a>;
           attribute <span>EventListener</span> <a href="#onconnect" title=handler-SharedWorkerGlobalScope-onconnect>onconnect</a>;
};</pre>

  <p class="no-ja-translation">Shared workers receive message ports through <code
   title=event-WorkerGlobalScope-connect>connect</code> events on their
   global object for each connection.

  <p class="no-ja-translation">The <dfn id=name
   title=dom-SharedWorkerGlobalScope-name><code>name</code></dfn> attribute
   must return the value it was assigned when the <code><a
   href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object
   was created by the "<a href="#run-a">run a worker</a>" algorithm. Its
   value represents the name that can be used to obtain a reference to the
   worker using the <code><a href="#sharedworker">SharedWorker</a></code>
   constructor.

  <p class="no-ja-translation">The following are the <span>event handler DOM attributes</span> that
   must be supported by objects implementing the <code><a
   href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
   interface:

  <dl>
   <dt class="no-ja-translation"><dfn id=onconnect
    title=handler-SharedWorkerGlobalScope-onconnect><code>onconnect</code></dfn>

   <dd>
    <p class="has-ja-translation"><span class=en-original lang=en>Must be invoked whenever a <code
     title=event-SharedWorkerGlobalScope-connect>connect</code> event is
     targeted at or bubbles through the <code><a
     href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
     object.
  </span><span class=ja-translation lang=ja><code title=event-SharedWorkerGlobalScope-connect>connect</code> 事象が当該 <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> オブジェクトを対象としているか、泡立って当該オブジェクトを通過する時に、
呼び出されなければなりません。</span></dl>

  <h3 id=base-urls class="has-ja-translation"><span class=en-original lang=en><span class=secno>2.2 </span>Base URLs and origins of
   workers</span><span class=ja-translation lang=ja><span class=secno>2.2 </span>労働者の基底 URL と起源</span></h3>

  <p class="no-ja-translation">The <span>base URL</span> of a <span>URL</span> passed to an API in a
   worker is the <span>absolute URL</span> given that the worker's <code
   title=dom-WorkerGlobalScope-location><a
   href="#location">location</a></code> attribute represents.

  <p class="no-ja-translation">Both the <span>origin</span> and <span>effective script origin</span> of
   scripts running in workers are the <span>origin</span> of the
   <span>absolute URL</span> given that the worker's <code
   title=dom-WorkerGlobalScope-location><a
   href="#location">location</a></code> attribute represents.

  <h3 id=the-queue class="has-ja-translation"><span class=en-original lang=en><span class=secno>2.3 </span>The queue of events</span><span class=ja-translation lang=ja><span class=secno>2.3 </span>事象の待ち行列</span></h3>

  <p class="no-ja-translation">Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
   object is asssociated with a <dfn id=queue>queue of events</dfn>, which is
   initially empty.

  <p class="has-ja-translation"><span class=en-original lang=en>An event in the queue can be a DOM event or a timeout callback.

  </span><span class=ja-translation lang=ja>待ち行列中の事象は、 DOM 事象か小休止呼び戻しのいずれかです。</span><p class="no-ja-translation">All asynchronous callbacks and events that would be called or dispatched
   in the worker must be added to the worker's queue, with the "<a
   href="#run-a">run a worker</a>" processing model below taking care of
   actually calling the callbacks or dispatching the events.

  <p class="no-ja-translation">Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
   object also has a <dfn id=closing
   title=dom-WorkerGlobalScope-closing>closing</dfn> flag, which must
   initially be false, but which can get set to true by the algorithms in the
   processing model section below.

  <p class="no-ja-translation">Once the <code><a
   href="#workerglobalscope">WorkerGlobalScope</a></code>'s <a
   href="#closing" title=dom-WorkerGlobalScope-closing>closing</a> flag is
   set to true, the queue must discard anything else that would be added to
   it. Effectively, once the <a href="#closing"
   title=dom-WorkerGlobalScope-closing>closing</a> flag is true, timers stop
   firing, notifications for all pending asynchronous operations are dropped,
   etc.

  <h3 id=the-workers class="has-ja-translation"><span class=en-original lang=en><span class=secno>2.4 </span>The worker's ports</span><span class=ja-translation lang=ja><span class=secno>2.4 </span>労働者のポート</span></h3>

  <p class="has-ja-translation"><span class=en-original lang=en>Workers communicate with other workers and with <span title="browsing
   context">browsing contexts</span> through <span title="channel
   messaging">message channels</span> and their <code>MessagePort</code>
   objects.

  </span><span class=ja-translation lang=ja>労働者は、メッセージ通信路とその <code>MessagePort</code>
オブジェクトを通じて、他の労働者や閲覧文脈と通信します。</span><p class="no-ja-translation">Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
   <var title="">worker global scope</var> has a list of <dfn
   id=the-workers0>the worker's ports</dfn>, which consists of all the
   <code>MessagePort</code> objects that are entangled with another port and
   that have one (but only one) port owned by <var title="">worker global
   scope</var>. This list includes all the <code>MessagePort</code> objects
   that are in events pending in the <a href="#queue">queue of events</a>, as
   well as the implicit <code>MessagePort</code> in the case of <a
   href="#dedicatedworkerglobalscope"
   title=DedicatedWorkerGlobalScope>dedicated workers</a>.

  <hr>

  <p class="no-ja-translation">A worker is said to be a <dfn id=permissible>permissible worker</dfn> if
   either:

  <ul>
   <li class="no-ja-translation">at some point past or present a <code>MessagePort</code> owned by the
    worker was entangled with a <code>MessagePort</code> <var
    title="">p</var> whose owner is a <code>Window</code> object whose
    <span>active document</span> is the <code>Document</code> that was that
    <span>browsing context</span>'s <span>active document</span> when <var
    title="">p</var> was created, and that <code>Document</code> is
    <span>fully active</span>, or

   <li class="no-ja-translation">at some point past or present a <code>MessagePort</code> owned by the
    worker was entangled with a <code>MessagePort</code> owned by another
    worker that is currently a <a href="#permissible">permissible worker</a>.
  </ul>

  <hr>

  <p class="no-ja-translation">A worker is said to be a <dfn id=protected>protected worker</dfn> if
   either:

  <ul>
   <li class="no-ja-translation">it has outstanding timers, database transactions, or network
    connections, and is a <a href="#permissible">permissible worker</a>, or:

   <li class="no-ja-translation">there is a <a href="#protected">protected worker</a> that at some
    point past or present owned a <code>MessagePort</code> that was entangled
    with a <code>MessagePort</code> owned by this worker.
  </ul>

  <hr>

  <p class="no-ja-translation">A worker is said to be an <dfn id=active>active needed worker</dfn> if
   either:

  <ul>
   <li class="no-ja-translation">the worker is a <a href="#protected">protected worker</a>, or

   <li class="no-ja-translation">at least one of the <a href="#the-workers0">the worker's ports</a> is
    entangled with a <code>MessagePort</code> <var title="">p</var> whose
    owner is a <code>Window</code> object whose <span>active document</span>
    is the <code>Document</code> that was that <span>browsing
    context</span>'s <span>active document</span> when that
    <code>MessagePort</code> <var title="">p</var> was created, and that
    <code>Document</code> is <span>fully active</span>, or

   <li class="no-ja-translation">at least one of the <a href="#the-workers0">the worker's ports</a> has
    an entangled <code>MessagePort</code> owned by a <code><a
    href="#workerglobalscope">WorkerGlobalScope</a></code> object that is
    itself an <a href="#active">active needed worker</a>.
  </ul>

  <hr>

  <p class="no-ja-translation">A worker is said to be a <dfn id=suspendable>suspendable worker</dfn> if
   it is not an <a href="#active">active needed worker</a> but either:

  <ul>
   <li class="no-ja-translation">at least one of the <a href="#the-workers0">the worker's ports</a> has
    an entangled <code>MessagePort</code> owned by a <code>Window</code>
    object, or

   <li class="no-ja-translation">at least one of the <a href="#the-workers0">the worker's ports</a> has
    an entangled <code>MessagePort</code> owned by a <code><a
    href="#workerglobalscope">WorkerGlobalScope</a></code> object that is
    itself a <span>needed worker</span>.
  </ul>

  <h3 id=processing class="has-ja-translation"><span class=en-original lang=en><span class=secno>2.5 </span>Processing model</span><span class=ja-translation lang=ja><span class=secno>2.5 </span>処理モデル</span></h3>

  <p class="no-ja-translation">When a user agent is to <dfn id=run-a>run a worker</dfn> for a script
   with <span>URL</span> <var title="">url</var>, a browsing context <var
   title="">owner browsing context</var>, a <code>Document</code> <var
   title="">owner document</var>, and with global scope <var title="">worker
   global scope</var>, it must run the following steps:

  <ol>
   <li>
    <p class="no-ja-translation">Create a completely separate and parallel execution environment (i.e.
     a separate thread or process or equivalent construct), and run the rest
     of these steps asychronously in that context.</p>

   <li>
    <p class="has-ja-translation"><span class=en-original lang=en>Attempt to <span>fetch</span><!-- XXX --> the resource identified by
     <var title="">url</var>.</span><span class=ja-translation lang=ja><var title="">url</var> で識別される資源を取って来ようと試みます。</span></p>

    <p class="no-ja-translation">If the attempt fails, then, at the next available opportunity, after
     any scripts have finished executing<!-- XXX queue -->, <span>fire a
     simple event</span> called <code title=event-error>error</code> at all
     <code><a href="#worker1">Worker</a></code> or <code><a
     href="#sharedworker">SharedWorker</a></code> objects associated with
     <var title="">worker global scope</var>. Abort these steps.</p>

    <p class="has-ja-translation"><span class=en-original lang=en>If the attempt succeeds, then let <var title="">script</var> be the
     resource that was obtained.</span><span class=ja-translation lang=ja>この試みが成功した場合、 <var title="">script</var>
を得られた資源とします。</span></p>

    <p class="note has-ja-translation"><span class=en-original lang=en>As with <code>script</code> elements, the MIME type of the
     script is ignored. Unlike with <code>script</code> elements, there is no
     way to override the type. It's always assumed to be JavaScript.</span><span class=ja-translation lang=ja><code>script</code> 要素と同様に、スクリプトの MIME 型は無視します。
<code>script</code> 要素とは異なり、
型を上書きする方法はありません。スクリプトは常に JavaScript
と仮定します。</span></p>
    <!-- XXX people will complain about
    this. I guess we might want to examine the MIME type... -->
    

   <li>
    <p class="no-ja-translation">Create a new <code><a href="#workerlocation">WorkerLocation</a></code>
     object for the <code title=dom-WorkerGlobalScope-location><a
     href="#location">location</a></code> attribute of <var title="">worker
     global scope</var>, representing <var title="">url</var>.</p>

   <li>
    <p class="no-ja-translation">Let <var title="">script</var>'s <span>script execution context</span>
     (and thus also <span>global object</span>) be <var title="">worker
     global scope</var>.</p>

   <li>
    <p class="has-ja-translation"><span class=en-original lang=en>Let <var title="">script</var>'s <span>script browsing context</span>
     be <var title="">owner browsing context</var>.</span><span class=ja-translation lang=ja><var title="">script</var> のスクリプト閲覧文脈を <var title="">owner browsing context</var>
とします。</span></p>

   <li>
    <p class="has-ja-translation"><span class=en-original lang=en>Let <var title="">script</var>'s <span>script document context</span>
     be <var title="">owner document</var>.</span><span class=ja-translation lang=ja><var title="">script</var> のスクリプト文書文脈を <var title="">owner document</var>
とします。</span></p>

   <li>
    <p class="no-ja-translation"><strong>Closing orphan workers</strong>: Start monitoring the worker
     such that as soon as it stops being either an <a href="#active">active
     needed worker</a> or a <a href="#suspendable">suspendable worker</a>,
     the <var title="">worker global scope</var>'s <a href="#closing"
     title=dom-WorkerGlobalScope-closing>closing</a> flag is set to true and
     an event named <code title=event-close>close</code>, which uses the
     <code>Event</code> object, which does not bubble, and which is not
     cancelable, is added it to <var title="">worker global scope</var>'s
     <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's
     <a href="#queue">queue of events</a>, targetted at the <var
     title="">worker global scope</var> itself.</p>

   <li>
    <p class="no-ja-translation"><strong>Suspending workers</strong>: Start monitoring the worker, such
     that whenever the <var title="">worker global scope</var>'s <a
     href="#closing" title=dom-WorkerGlobalScope-closing>closing</a> flag is
     false and the worker is a <a href="#suspendable">suspendable worker</a>,
     the user agent suspends execution of script in that worker until such
     time as either the <a href="#closing"
     title=dom-WorkerGlobalScope-closing>closing</a> flag switches to true or
     the worker stops being a <a href="#suspendable">suspendable worker</a>.</p>

   <li>
    <p class="no-ja-translation">Run <var title="">script</var> until it either returns, fails to catch
     an exception, or gets prematurely aborted by the "<a href="#kill-a">kill
     a worker</a>" or "<a href="#terminate">terminate a worker</a>"
     algorithms defined below.</p>

    <p class="note no-ja-translation">If the script gets aborted by the "<a href="#kill-a">kill a
     worker</a>" algorithm, then that same algorithm will cause there to only
     be a single event in the <a href="#queue">queue of events</a> at the
     next step, namely the <code title=message-close>close</code> event. The
     "<a href="#terminate">terminate a worker</a>" algorithm removes all the
     events.</p>

   <li>
    <p class="no-ja-translation"><i>Event loop</i>: Wait until either there is an event in the <a
     href="#queue">queue of events</a> associated with <var title="">worker
     global scope</var> or the <var title="">worker global scope</var>'s <a
     href="#closing" title=dom-WorkerGlobalScope-closing>closing</a> flag is
     set to true.</p>

   <li>
    <p class="no-ja-translation">Dispatch the oldest event or callback in the <a href="#queue">queue of
     events</a>, if any. The handling of this event or the execution of this
     callback might get prematurely aborted by the "<a href="#kill-a">kill a
     worker</a>" or "<a href="#terminate">terminate a worker</a>" algorithms
     defined below.</p>

   <li>
    <p class="no-ja-translation">If there are any more events in the <a href="#queue">queue of
     events</a> or if the <var title="">worker global scope</var>'s <a
     href="#closing" title=dom-WorkerGlobalScope-closing>closing</a> flag is
     set to false, then jump back to the step above labeled <i>event
     loop</i>.</p>

   <li>
    <p class="big-issue no-ja-translation">timers, intervals, XMLHttpRequests, database
     transactions, etc, must be killed; ports must be unentangled</p>

   <li>
    <p class="no-ja-translation">At the next available opportunity, after any scripts have finished
     executing<!-- XXX queue -->, <span>fire a simple event</span> called
     <code title=event-close>close</code> at all <code><a
     href="#worker1">Worker</a></code> or <code><a
     href="#sharedworker">SharedWorker</a></code> objects associated with
     this worker.</p>
  </ol>

  <hr>

  <p class="no-ja-translation">When a user agent is to <dfn id=kill-a>kill a worker</dfn> it must run
   the following steps in parallel with the worker's main loop (the "<a
   href="#run-a">run a worker</a>" processing model defined above):

  <ol>
   <li>
    <p class="no-ja-translation">Create an <code>Event</code> object with the event name <code
     title=event-close>close</code>, which does not bubble and is not
     cancelable, and add it to the worker's <code><a
     href="#workerglobalscope">WorkerGlobalScope</a></code> object's <a
     href="#queue">queue of events</a>, targetted at the <code><a
     href="#workerglobalscope">WorkerGlobalScope</a></code> object itself.
   </li>
   <!-- XXX shouldn't add one if closing is
   already true, assuming close has already been added to the queue
   (?) -->

   <li>
    <p class="no-ja-translation">Set the worker's <code><a
     href="#workerglobalscope">WorkerGlobalScope</a></code> object's <a
     href="#closing" title=dom-WorkerGlobalScope-closing>closing</a> flag to
     true.

   <li>
    <p class="no-ja-translation">Wait a user-agent-defined amount of time. If the "<a href="#run-a">run
     a worker</a>" processing model defined above immediately starts running
     event listeners registered for the <code title=event-close>close</code>
     event, this time should not be zero &mdash; the idea is that the <code
     title=event-close>close</code> event can be used to clean up when
     shutting down unexpectedly.

   <li>
    <p class="no-ja-translation">If there are any events in the <a href="#queue">queue of events</a>
     other than the <code title=event-close>close</code> event that this
     algorithm just added, discard them without dispatching them.

   <li>
    <p class="no-ja-translation">If the <code title=event-close>close</code> event that this algorithm
     just added hasn't yet been dispatched, then abort the script currently
     running in the worker.

   <li>
    <p class="has-ja-translation"><span class=en-original lang=en>Wait a user-agent-defined amount of time.

   </span><span class=ja-translation lang=ja>利用者エージェント定義の時間、待ちます。</span><li>
    <p class="no-ja-translation">Abort the script currently running in the worker (if any script is
     running, then it will be a handler for the <code
     title=event-close>close</code> event).
  </ol>

  <p class="no-ja-translation">User agents may invoke the "<a href="#kill-a">kill a worker</a>"
   processing model on a worker at any time, e.g. in response to user
   requests, in response to CPU quota management, or when a worker stops
   being an <a href="#active">active needed worker</a> if the worker
   continues executing even after its <a href="#closing"
   title=dom-WorkerGlobalScope-closing>closing</a> flag was set to true.

  <hr>

  <p class="no-ja-translation">When a user agent is to <dfn id=terminate>terminate a worker</dfn> it
   must run the following steps in parallel with the worker's main loop (the
   "<a href="#run-a">run a worker</a>" processing model defined above):

  <ol>
   <li>
    <p class="no-ja-translation">Set the worker's <code><a
     href="#workerglobalscope">WorkerGlobalScope</a></code> object's <a
     href="#closing" title=dom-WorkerGlobalScope-closing>closing</a> flag to
     true.

   <li>
    <p class="no-ja-translation">If there are any events in the <a href="#queue">queue of events</a>
     other than the <code title=event-close>close</code> event that this
     algorithm just added, discard them without dispatching them.

   <li>
    <p class="no-ja-translation">Abort the script currently running in the worker.
  </ol>

  <h3 id=creating class="has-ja-translation"><span class=en-original lang=en><span class=secno>2.6 </span>Creating workers</span><span class=ja-translation lang=ja><span class=secno>2.6 </span>労働者の作成</span></h3>

  <h4 id=the-abstractworker class="has-ja-translation"><span class=en-original lang=en><span class=secno>2.6.1 </span>The <code><a
   href="#abstractworker">AbstractWorker</a></code> abstract interface</span><span class=ja-translation lang=ja><span class=secno>2.6.1 </span><code><a href="#abstractworker">AbstractWorker</a></code> abstract 界面</span></h4>

  <pre
   class="idl no-ja-translation">[NoInterfaceObject] interface <dfn id=abstractworker>AbstractWorker</dfn> {
           attribute <span>EventListener</span> <a href="#onerror" title=handler-AbstractWorker-onerror>onerror</a>;
           attribute <span>EventListener</span> <a href="#onclose0" title=handler-AbstractWorker-onclose>onclose</a>;
};</pre>

  <p class="no-ja-translation">The following are the <span>event handler DOM attributes</span> that
   must be supported by objects implementing the <code><a
   href="#abstractworker">AbstractWorker</a></code> interface:

  <dl>
   <dt class="no-ja-translation"><dfn id=onerror
    title=handler-AbstractWorker-onerror><code>onerror</code></dfn>

   <dd>
    <p class="no-ja-translation">Must be invoked whenever an <code title=event-error>error</code> event
     is targeted at or bubbles through the <code><a
     href="#abstractworker">AbstractWorker</a></code> object.

   <dt class="no-ja-translation"><dfn id=onclose0
    title=handler-AbstractWorker-onclose><code>onclose</code></dfn>

   <dd>
    <p class="no-ja-translation">Must be invoked whenever an <code title=event-close>close</code> event
     is targeted at or bubbles through the <code><a
     href="#abstractworker">AbstractWorker</a></code> object.
  </dl>

  <h4 id=dedicated0 class="no-ja-translation"><span class=secno>2.6.2 </span>Dedicated workers and the
   <code><a href="#worker1">Worker</a></code> interface</h4>

  <pre class="idl no-ja-translation">[NoInterfaceObject,
 <a href="#worker2" title=dom-Worker>Constructor</a>(in DOMString scriptURL)]
interface <dfn id=worker1>Worker</dfn> : <a href="#abstractworker">AbstractWorker</a> {
  void <a href="#close0" title=dom-Worker-close>close</a>();

  void <a href="#postmessage0" title=dom-Worker-postMessage>postMessage</a>(in DOMString message);
  void <a href="#postmessage0" title=dom-Worker-postMessage>postMessage</a>(in DOMString message, in <span>MessagePort</span> messagePort);
  <span>MessagePort</span> <a href="#startconversation0" title=dom-Worker-startConversation>startConversation</a>(in DOMString message);
           attribute <span>EventListener</span> <a href="#onmessage0" title=handler-Worker-onmessage>onmessage</a>;
};</pre>

  <p class="no-ja-translation">The <dfn id=close0 title=dom-Worker-close><code>close()</code></dfn>
   method, when invoked, must cause the "<a href="#terminate">terminate a
   worker</a>" algorithm to be run on the worker with with the object is
   associated.

  <p class="no-ja-translation"><code><a href="#worker1">Worker</a></code> objects act as if they had an
   implicit <code>MessagePort</code> associated with them. This port is part
   of a channel that is set up when the worker is created, but it is not
   exposed. This object must never be garbage collected before the <code><a
   href="#worker1">Worker</a></code> object.

  <p class="no-ja-translation">All messages received by that port must immediately be retargetted at
   the <code><a href="#worker1">Worker</a></code> object.

  <p class="no-ja-translation">The <dfn id=postmessage0
   title=dom-Worker-postMessage><code>postMessage()</code></dfn> and <dfn
   id=startconversation0
   title=dom-Worker-startConversation><code>startConversation()</code></dfn>
   methods on <code><a href="#worker1">Worker</a></code> objects must act as
   if, when invoked, they immediately invoked the method of the same name on
   the port, with the same arguments, and returned the same return value.

  <p class="no-ja-translation">The following are the <span>event handler DOM attributes</span> that
   must be supported by objects implementing the <code><a
   href="#worker1">Worker</a></code> interface:

  <dl>
   <dt class="no-ja-translation"><dfn id=onmessage0
    title=handler-Worker-onmessage><code>onmessage</code></dfn>

   <dd>
    <p class="has-ja-translation"><span class=en-original lang=en>Must be invoked whenever a <code
     title=event-Worker-message>message</code> event is targeted at or
     bubbles through the <code><a href="#worker1">Worker</a></code> object.
  </span><span class=ja-translation lang=ja><code title=event-Worker-message>message</code> 事象が当該 <code><a href="#worker1">Worker</a></code> オブジェクトを対象としているか、泡立って当該オブジェクトを通過する時に、
呼び出されなければなりません。</span></dl>

  <hr>

  <p class="no-ja-translation">When the <dfn id=worker2 title=dom-Worker><code>Worker(<var
   title="">scriptURL</var>)</code></dfn> constructor is invoked, the user
   agent must run the following steps:

  <ol>
   <li>
    <p class="has-ja-translation"><span class=en-original lang=en><span title="resolve a url">Resolve</span> the <var
     title="">scriptURL</var> argument.

   </span><span class=ja-translation lang=ja><var
     title="">scriptURL</var> 引数を<span title="resolve a url">解決</span>します。</span><li>
    <p class="has-ja-translation"><span class=en-original lang=en>If this fails, throw a <code>SYNTAX_ERR</code> exception.

   </span><span class=ja-translation lang=ja>これが失敗した場合、 <code>SYNTAX_ERR</code>
例外を投げます。</span><li>
    <p class="no-ja-translation">If the <span>origin</span> of the resulting <span>absolute URL</span>
     is not the <span title="same origin">same</span> as the origin of the
     script that invoked the constructor, then throw a <span>security
     exception</span>.

   <li>
    <p class="no-ja-translation"><span>Create a new <code><a
     href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
     object</span>. Let this be the <var title="">worker global scope</var>.

   <li>
    <p class="no-ja-translation">Create a new <code><a href="#worker1">Worker</a></code> object,
     associated with <var title="">worker global scope</var>. Let this
     <code><a href="#worker1">Worker</a></code> object be <var
     title="">worker</var>.

   <li>
    <p class="no-ja-translation"><span>Create a <code>MessagePort</code> object</span> owned by the
     <span>script execution context</span> of the script that invoked the
     method. Let this be the <var title="">outside port</var>.

   <li>
    <p class="no-ja-translation">Associate the <var title="">outside port</var> with <var
     title="">worker</var>.

   <li>
    <p class="no-ja-translation"><span>Create a <code>MessagePort</code> object</span> owned by the
     <var title="">worker global scope</var>. Let this be the <var
     title="">inside port</var>.

   <li>
    <p class="no-ja-translation">Associate the <var title="">inside port</var> with <var
     title="">worker global scope</var>.

   <li>
    <p class="no-ja-translation"><span>Entangle</span> <var title="">outside port</var> and <var
     title="">inside port</var>.

   <li>
    <p class="no-ja-translation">Return <var title="">worker</var>, and run the following steps
     asynchronously.

   <li>
    <p class="no-ja-translation">Open <var title="">inside port</var>'s <span>port message
     queue</span>.

   <li>
    <p class="no-ja-translation">Open <var title="">outside port</var>'s <span>port message
     queue</span>.

   <li>
    <p class="no-ja-translation"><a href="#run-a">Run a worker</a>, with the <span>script browsing
     context</span> of the script that invoked the method as the <var
     title="">owner browsing context</var>, with the <span>script document
     context</span> of the script that invoked the method as the <var
     title="">owner document</var>, and with <var title="">worker global
     scope</var> as the global scope.</p>
  </ol>

  <h4 id=shared1 class="no-ja-translation"><span class=secno>2.6.3 </span>Shared workers and the
   <code><a href="#sharedworker">SharedWorker</a></code> interface</h4>

  <pre class="idl no-ja-translation">[NoInterfaceObject,
 <a href="#sharedworker0" title=dom-SharedWorker>Constructor</a>(in DOMString scriptURL, in DOMString name)]
interface <dfn id=sharedworker>SharedWorker</dfn> : <a href="#abstractworker">AbstractWorker</a> {
  readonly attribute <code>MessagePort</code> <a href="#port" title=dom-SharedWorker-port>port</a>;
};</pre>

  <p class="no-ja-translation">The <dfn id=port title=dom-SharedWorker-port><code>port</code></dfn>
   attribute must return the value it was assigned by the object's
   constructor. It represents the <code>MessagePort</code> for communicating
   with the shared worker.

  <p class="no-ja-translation">When the <dfn id=sharedworker0
   title=dom-SharedWorker><code>SharedWorker(<var title="">scriptURL</var>,
   <var title="">name</var>)</code></dfn> constructor is invoked, the user
   agent must run the following steps:

  <ol>
   <li>
    <p class="has-ja-translation"><span class=en-original lang=en><span title="resolve a url">Resolve</span> the <var
     title="">scriptURL</var> argument.

   </span><span class=ja-translation lang=ja><var
     title="">scriptURL</var> 引数を<span title="resolve a url">解決</span>します。</span><li>
    <p class="has-ja-translation"><span class=en-original lang=en>If this fails, throw a <code>SYNTAX_ERR</code> exception.

   </span><span class=ja-translation lang=ja>これが失敗した場合、 <code>SYNTAX_ERR</code>
例外を投げます。</span><li>
    <p class="no-ja-translation">If the <span>origin</span> of the resulting <span>absolute URL</span>
     is not the <span title="same origin">same</span> as the origin of the
     script that invoked the constructor, then throw a <span>security
     exception</span>.

   <li>
    <p class="no-ja-translation">Execute the following substeps atomically:</p>

    <ol>
     <li>
      <p class="no-ja-translation">Create a new <code><a href="#sharedworker">SharedWorker</a></code>
       object, which will shortly be associated with a <code><a
       href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
       object. Let this <code><a href="#sharedworker">SharedWorker</a></code>
       object be <var title="">worker</var>.

     <li>
      <p class="no-ja-translation"><span>Create a <code>MessagePort</code> object</span> owned by the
       <span>script execution context</span> of the script that invoked the
       method. Let this be the <var title="">outside port</var>.

     <li>
      <p class="no-ja-translation">Assign <var title="">outside port</var> to the <code
       title=dom-SharedWorker-port><a href="#port">port</a></code> attribute
       of <var title="">worker</var>.

     <li>
      <p class="no-ja-translation">If there exists a <code><a
       href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
       object whose <a href="#closing"
       title=dom-WorkerGlobalScope-closing>closing</a> flag is false, whose
       <code title=dom-WorkerGlobalScope-name>name</code> attribute is
       exactly equal to the <var title="">name</var> argument, and whose
       <code title=dom-WorkerGlobalScope-location><a
       href="#location">location</a></code> attribute represents an
       <span>absolute URL</span> that has the <span>same origin</span> as the
       resulting <span>absolute URL</span>, then run these substeps:</p>

      <ol>
       <li>
        <p class="no-ja-translation">Let <var title="">worker global scope</var> be that <code><a
         href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
         object.

       <li>
        <p class="no-ja-translation">If <var title="">worker global scope</var>'s <code
         title=dom-WorkerGlobalScope-location><a
         href="#location">location</a></code> attribute represents an
         <span>absolute URL</span> that is not exactly equal to the resulting
         <span>absolute URL</span>, then throw a
         <code>URL_MISMATCH_ERR</code> exception and abort all these steps.
         <span class=big-issue>code 21</span>

       <li>
        <p class="no-ja-translation">Associate <var title="">worker</var> with <var title="">worker
         global scope</var>.

       <li>
        <p class="no-ja-translation"><span>Create a <code>MessagePort</code> object</span> owned by the
         <var title="">worker global scope</var>. Let this be the <var
         title="">inside port</var>.

       <li>
        <p class="no-ja-translation"><span>Entangle</span> <var title="">outside port</var> and <var
         title="">inside port</var>.

       <li>
        <p class="no-ja-translation">Return <var title="">worker</var> and perform the next step
         asynchronously.

       <li>
        <p class="no-ja-translation">Create an event that uses the <code>MessageEvent</code> interface,
         with the name <code title=event-connect>connect</code>, which does
         not bubble, is cancelable, has no default action, has a <code
         title=dom-MessageEvent-data>data</code> attribute whose value is the
         empty string and has a <code
         title=dom-MessageEvent-messagePort>messagePort</code> attribute
         whose value is the newly created port, and add it to <var
         title="">worker global scope</var>'s <a href="#queue">queue of
         events</a>, targetted at the <var title="">worker global scope</var>
         itself.

       <li>
        <p class="no-ja-translation">Abort all these steps.
      </ol>

     <li>
      <p class="no-ja-translation"><span>Create a new <code><a
       href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
       object</span>. Let this be the <var title="">worker global
       scope</var>.

     <li>
      <p class="no-ja-translation">Associate <var title="">worker</var> with <var title="">worker
       global scope</var>.

     <li>
      <p class="no-ja-translation">Set the <code title=dom-SharedWorkerGlobalScope-name><a
       href="#name">name</a></code> attribute of <var title="">worker global
       scope</var> be <var title="">name</var>.

     <li>
      <p class="no-ja-translation"><span>Create a <code>MessagePort</code> object</span> owned by the
       <var title="">worker global scope</var>. Let this be the <var
       title="">inside port</var>.

     <li>
      <p class="no-ja-translation"><span>Entangle</span> <var title="">outside port</var> and <var
       title="">inside port</var>.
    </ol>

   <li>
    <p class="no-ja-translation">Return <var title="">worker</var> and perform the next step
     asynchronously.

   <li>
    <p class="no-ja-translation">Create an event that uses the <code>MessageEvent</code> interface,
     with the name <code title=event-connect>connect</code>, which does not
     bubble, is cancelable, has no default action, has a <code
     title=dom-MessageEvent-data>data</code> attribute whose value is the
     empty string and has a <code
     title=dom-MessageEvent-messagePort>messagePort</code> attribute whose
     value is the newly created port, and add it to <var title="">worker
     global scope</var>'s <a href="#queue">queue of events</a>, targetted at
     the <var title="">worker global scope</var> itself.

   <li>
    <p class="no-ja-translation"><a href="#run-a">Run a worker</a>, with the <span>script browsing
     context</span> of the script that invoked the method as the <var
     title="">owner browsing context</var>, with the <span>script document
     context</span> of the script that invoked the method as the <var
     title="">owner document</var>, and with <var title="">worker global
     scope</var> as the global scope.</p>
  </ol>

  <h2 id=apis-available class="has-ja-translation"><span class=en-original lang=en><span class=secno>3. </span>APIs available to workers</span><span class=ja-translation lang=ja><span class=secno>3. </span>労働者が利用可能な API</span></h2>

  <pre
   class="idl no-ja-translation">[NoInterfaceObject] interface <dfn id=workerutils>WorkerUtils</dfn> {
  void <a href="#importscripts" title=dom-WorkerGlobalScope-importScripts>importScripts</a>([Variadic] in DOMString urls);
  readonly attribute <span>Storage</span> <a href="#localstorage" title=dom-localStorage>localStorage</a>;
  <span>Database</span> <a href="#opendatabase" title=dom-opendatabase>openDatabase</a>(in DOMString name, in DOMString version, in DOMString displayName, in unsigned long estimatedSize);
  void <a href="#shownotification" title=dom-showNotification>showNotification</a>(in DOMString title, in DOMString subtitle, in DOMString description);
  void <a href="#shownotification" title=dom-showNotification>showNotification</a>(in DOMString title, in DOMString subtitle, in DOMString description, in VoidCallback onclick);
};</pre>

  <p class="has-ja-translation"><span class=en-original lang=en>Objects that implement the <code><a
   href="#workerglobalscope">WorkerGlobalScope</a></code> interface must also
   implement the <code><a href="#workerutils">WorkerUtils</a></code>
   interface.

  </span><span class=ja-translation lang=ja><code><a href="#workerglobalscope">WorkerGlobalScope</a></code> 界面を実装するオブジェクトは、 <code><a href="#workerutils">WorkerUtils</a></code> 界面も実装しなければ<em class=rfc2119 title="MUST">なりません</em>。</span><p class="big-issue no-ja-translation">Need to define a sync database API.

  <p class="big-issue no-ja-translation">May need to define a browser sniffing API (like
   window.navigator).</p>
  <!-- XXX ApplicationCache -->
  <!-- XXX a way to set cookies on the URL for the script -->
  <!-- XXX debugging: void log(in DOMString s); // log to console -->
  <!-- XXX debugging: onerror -->

  <hr>

  <p class="has-ja-translation"><span class=en-original lang=en>The DOM APIs (<code>Node</code> objects, <code>Document</code> objects,
   etc) are not available to workers in this version of this specification.

  </span><span class=ja-translation lang=ja>DOM API (<code>Node</code> オブジェクト、 <code>Document</code>
オブジェクト、その他) は、この版のこの仕様書では労働者に利用可能ではありません。</span><h3 id=importing class="no-ja-translation"><span class=secno>3.1 </span>Importing scripts and
   libraries</h3>

  <p class="no-ja-translation">When a script invokes the <dfn id=importscripts
   title=dom-WorkerGlobalScope-importScripts><code>importScripts(<var
   title="">urls</var>)</code></dfn> method on a <code><a
   href="#workerglobalscope">WorkerGlobalScope</a></code> object, the user
   agent must run the following steps:

  <ol>
   <li>
    <p class="no-ja-translation">If there are no arguments, return without doing anything. Abort these
     steps.

   <li>
    <p class="no-ja-translation"><span title="resolve a url">Resolve</span> each argument.

   <li>
    <p class="no-ja-translation">If any fail, throw a <code>SYNTAX_ERR</code> exception.

   <li>
    <p class="no-ja-translation">If any of the resulting <span title="absolute URL">absolute
     URLs</span> have an <span>origin</span> that is not the <span
     title="same origin">same</span> as the origin of the script that invoked
     the method, then throw a <span>security exception</span>.

   <li>
    <p class="no-ja-translation">Attempt to <span>fetch</span> each resource identified by the
     resulting <span title="absolute URLs">absolute URL</span>.</p>

   <li>
    <p class="no-ja-translation">For each argument in turn, in the order given, starting with the first
     one, run these substeps:</p>

    <ol>
     <li>
      <p class="no-ja-translation">Wait for the fetching attempt for the corresponding resource to
       complete.</p>

      <p class="no-ja-translation">If the fetching attempt failed, throw a <code>NETWORK_ERR</code>
       exception and abort all these steps. <a
       href="#refsXHR">[XHR]</a><!-- XXX get DOM Core updated instead
      --></p>

      <p class="no-ja-translation">If the fetching attempt succeeded, then let <var
       title="">script</var> be the resource that was obtained.</p>

      <p class="note no-ja-translation">As with the worker's script, the script here is always
       assumed to be JavaScript, regardless of the MIME type.</p>
      <!-- XXX -->

     <li>
      <p class="no-ja-translation">Let <var title="">script</var>'s <span>script execution
       context</span>, <span>script browsing context</span>, and <span>script
       document context</span> be the same as for the script that was
       executed by the <a href="#run-a">run a worker</a> processing model for
       this worker.</p>

     <li>
      <p class="no-ja-translation">Run <var title="">script</var> until it either returns, fails to
       catch an exception, or gets prematurely aborted by the "<a
       href="#kill-a">kill a worker</a>" or "<a href="#terminate">terminate a
       worker</a>" algorithms defined above.</p>

      <p class="no-ja-translation">If an exception was raised or if the script was prematurely aborted,
       then abort all these steps, letting the exception or aborting continue
       to be processed by the script that called the <code
       title=dom-WorkerGlobalScope-importScripts><a
       href="#importscripts">importScripts()</a></code> method.</p>

      <p class="no-ja-translation">If the "<a href="#kill-a">kill a worker</a>" or "<a
       href="#terminate">terminate a worker</a>" algoriths abort the script
       then abort all these steps.</p>
    </ol>
  </ol>

  <h3 id=apis-defined class="no-ja-translation"><span class=secno>3.2 </span>APIs defined in other
   specifications</h3>

  <p class="no-ja-translation">The <dfn id=localstorage
   title=dom-localStorage><code>localStorage</code></dfn>, <dfn
   id=opendatabase title=dom-opendatabase><code>openDatabase()</code></dfn>
   must act as defined for the APIs with the same names on the
   <code>Window</code> object in the HTML5 specification, with the exception
   that where the API would use the <span>origin</span> of the <span>active
   document</span> of the <span>browsing context</span> of the
   <code>Window</code> object on which the method was supposedly invoked, it
   must instead use the <span>origin</span> of the script that invoked the
   method. <a href="#refsHTML5">[HTML5]</a>

  <p class="no-ja-translation">The <dfn id=shownotification
   title=dom-showNotification><code>showNotification()</code></dfn> methods
   must act as defined for the APIs with the same names on the
   <code>Window</code> object in the HTML5 specification. <a
   href="#refsHTML5">[HTML5]</a>

  <h3 id=interface class="no-ja-translation"><span class=secno>3.3 </span>Interface objects and
   constructors</h3>

  <p class="no-ja-translation">There must be no interface objects and constructors available in the
   global scope of scripts whose <span>script execution context</span> is a
   <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object
   except for the following:

  <ul>
   <li>
    <p class="no-ja-translation"><code>XMLHttpRequest</code> and all interface objects and constructors
     defined by the XMLHttpRequest specifications, except that the
     <span>document response entity body</span> must always be null. <a
     href="#refsXHR">[XHR]</a>

   <li>
    <p class="has-ja-translation"><span class=en-original lang=en>The <code>WebSocket</code> interface object and constructor.

   </span><span class=ja-translation lang=ja><code>WebSocket</code> 界面オブジェクトと構築器</span><li>
    <p class="has-ja-translation"><span class=en-original lang=en>The <code>MessageChannel</code> interface object and constructor.
  </span><span class=ja-translation lang=ja><code>MessageChannel</code> 界面オブジェクトと構築器</span></ul>

  <h3 id=worker0 class="no-ja-translation"><span class=secno>3.4 </span>Worker locations</h3>

  <pre
   class="idl no-ja-translation">[NoInterfaceObject] interface <dfn id=workerlocation>WorkerLocation</dfn> {
  readonly attribute DOMString <a href="#href" title=dom-WorkerLocation-href>href</a>;
  readonly attribute DOMString <a href="#protocol" title=dom-WorkerLocation-protocol>protocol</a>;
  readonly attribute DOMString <a href="#host" title=dom-WorkerLocation-host>host</a>;
  readonly attribute DOMString <a href="#hostname" title=dom-WorkerLocation-hostname>hostname</a>;
  readonly attribute DOMString <a href="#port0" title=dom-WorkerLocation-port>port</a>;
  readonly attribute DOMString <a href="#pathname" title=dom-WorkerLocation-pathname>pathname</a>;
  readonly attribute DOMString <a href="#search" title=dom-WorkerLocation-search>search</a>;
  readonly attribute DOMString <a href="#hash" title=dom-WorkerLocation-hash>hash</a>;
};</pre>

  <p class="no-ja-translation">A <code><a href="#workerlocation">WorkerLocation</a></code> object
   represents an <span>absolute URL</span> set at its creation.

  <p class="no-ja-translation">The <dfn id=href title=dom-WorkerLocation-href><code>href</code></dfn>
   attribute must return the <span>absolute URL</span> that the object
   represents.

  <p class="no-ja-translation">The <code><a href="#workerlocation">WorkerLocation</a></code> interface
   also has the complement of <span>URL decomposition attributes</span>, <dfn
   id=protocol title=dom-WorkerLocation-protocol><code>protocol</code></dfn>,
   <dfn id=host title=dom-WorkerLocation-host><code>host</code></dfn>, <dfn
   id=port0 title=dom-WorkerLocation-port><code>port</code></dfn>, <dfn
   id=hostname title=dom-WorkerLocation-hostname><code>hostname</code></dfn>,
   <dfn id=pathname
   title=dom-WorkerLocation-pathname><code>pathname</code></dfn>, <dfn
   id=search title=dom-WorkerLocation-search><code>search</code></dfn>, and
   <dfn id=hash title=dom-WorkerLocation-hash><code>hash</code></dfn>. These
   must follow the rules given for URL decomposition attributes, with the
   <span title=concept-uda-input>input</span> being the <span>absolute
   URL</span> that the object represents (same as the <code
   title=dom-WorkerLocation-href><a href="#href">href</a></code> attribute),
   and the <span title=concept-uda-setter>common setter action</span> being a
   no-op, since the attributes are defined to be readonly. <a
   href="#refsHTML5">[HTML5]</a>

  <h2 class="no-num has-ja-translation" id=references><span class=en-original lang=en>References</span><span class=ja-translation lang=ja>参考文献</span></h2>

  <p class="big-issue has-ja-translation"><span class=en-original lang=en>This section will be written in a future
   draft.<!--XXX-->

  </span><span class=ja-translation lang=ja>この章は将来の仕様案で執筆します。</span><h2 class="no-num has-ja-translation" id=acknowledgements><span class=en-original lang=en>Acknowledgements</span><span class=ja-translation lang=ja>謝辞</span></h2>
  <!-- ACKS -->

  <p class="has-ja-translation"><span class=en-original lang=en>Thanks to Aaron Boodman, Jonas Sicking, Justin James, Maciej Stachowiak,
   Mike Smith, and Philip Taylor for their useful and substantial comments.

  </span><span class=ja-translation lang=ja>Aaron Boodman, Jonas Sicking, Justin James, Maciej Stachowiak, Mike Smith, Philip Taylor の有用かつ重要なコメントに感謝します。</span><p class="has-ja-translation"><span class=en-original lang=en>Huge thanks to the whole Gears team, who pioneered this technology and
   whose experience has been a huge influence on this specification.
</span><span class=ja-translation lang=ja>Gears チームの方々にも非常に感謝します。
Gears チームの方々はこの技術を開拓し、その経験はこの仕様書にも多大な影響を与えています。
</span>