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<body class="h-entry" style="" role="document" id="respecDocument"><div class="head" role="contentinfo" id="respecHeader">
<p>
<a href="http://www.w3.org/"><img width="72" height="48" src="https://www.w3.org/Icons/w3c_home" alt="W3C"></a>
</p>
<h1 class="title p-name" id="title" property="dcterms:title">Input Method Editor API</h1>
<h2 property="dcterms:issued" datatype="xsd:dateTime" content="2013-12-17T00:00:00.000Z" id="w3c-working-draft-15-december-2013"><abbr title="World Wide Web Consortium">W3C</abbr> Working Draft <time class="dt-published" datetime="2013-12-17">17 December 2013</time></h2>
<dl>
<dt>This version:</dt>
<dd><a class="u-url" href="http://www.w3.org/TR/2013/WD-ime-api-20131217/">http://www.w3.org/TR/2013/WD-ime-api-20131217/</a></dd>
<dt>Latest published version:</dt>
<dd><a href="http://www.w3.org/TR/ime-api/">http://www.w3.org/TR/ime-api/</a></dd>
<dt>Previous versions:</dt>
<dd><a href="http://www.w3.org/TR/2013/WD-ime-api-20130815/">http://www.w3.org/TR/2013/WD-ime-api-20130815/</a></dd>
<dd><a href="http://www.w3.org/TR/2013/WD-ime-api-20130404/">http://www.w3.org/TR/2013/WD-ime-api-20130404/</a></dd>
<dd><a href="http://www.w3.org/TR/2012/WD-ime-api-20120524/">http://www.w3.org/TR/2012/WD-ime-api-20120524/</a></dd>
<dt>Latest editor's draft:</dt>
<dd><a href="http://dvcs.w3.org/hg/ime-api/raw-file/default/Overview.html">http://dvcs.w3.org/hg/ime-api/raw-file/default/Overview.html</a></dd>
<dt>Editors:</dt>
<dd class="p-author h-card vcard" rel="bibo:editor" inlist=""><span typeof="foaf:Person"><span property="foaf:name" class="p-name fn">Takayoshi Kochi</span>, Google, <span class="ed_mailto"><a class="u-email email" rel="foaf:mbox" href="mailto:kochi@google.com">kochi@google.com</a></span></span>
</dd>
<dd class="p-author h-card vcard" rel="bibo:editor" inlist=""><span typeof="foaf:Person"><span property="foaf:name" class="p-name fn">Kenji Baheux</span>, Google, <span class="ed_mailto"><a class="u-email email" rel="foaf:mbox" href="mailto:kenjibaheux@google.com">kenjibaheux@google.com</a></span></span>
</dd>
<dt>Previous editor:</dt>
<dd class="p-author h-card vcard" rel="bibo:editor" inlist=""><span typeof="foaf:Person"><span property="foaf:name" class="p-name fn">Hironori Bono (坊野 博典)</span>, (formerly) Google</span>
</dd>
</dl>
<p class="copyright">
<a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> ©
2013
<a href="http://www.w3.org/"><abbr title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup>
(<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts Institute of Technology">MIT</abbr></a>,
<a href="http://www.ercim.eu/"><abbr title="European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>,
<a href="http://www.keio.ac.jp/">Keio</a>, <a href="http://ev.buaa.edu.cn/">Beihang</a>),
All Rights Reserved.
<abbr title="World Wide Web Consortium">W3C</abbr> <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
<a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and
<a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a>
rules apply.
</p>
<hr>
</div>
<section id="abstract" class="introductory" property="dcterms:abstract" datatype="" typeof="bibo:Chapter" resource="#ref" rel="bibo:Chapter"><h2 aria-level="1" role="heading" id="h2_abstract">Abstract</h2>
<p>This specification defines an “IME API” that provides
Web applications with scripted access to an IME
(<a href="#IME">input-method editor</a>) associated with
a hosting user agent. This IME API includes:</p>
<ul>
<li>An <a href="#idl-def-InputMethodContext" class="idlType"><code>InputMethodContext</code></a> interface, which provides
attributes, events, and methods to interact
with current UI state of IME.
</li>
</ul>
<p>This API is designed to be used in conjunction with DOM events
[<cite><a class="bibref" href="#bib-DOM-LEVEL-3-EVENTS">DOM-LEVEL-3-EVENTS</a></cite>].</p>
</section><section id="sotd" class="introductory" typeof="bibo:Chapter" resource="#ref" rel="bibo:Chapter"><h2 aria-level="1" role="heading" id="h2_sotd">Status of This Document</h2>
<p>
<em>This section describes the status of this document at the time of its publication.
Other documents may supersede this document. A list of current <abbr title="World Wide Web Consortium">W3C</abbr> publications and the
latest revision of this technical report can be found in the <a href="http://www.w3.org/TR/"><abbr title="World Wide Web Consortium">W3C</abbr> technical reports index</a> at
http://www.w3.org/TR/.</em>
</p>
<p>
This document is a proposal that is being made available for public
review in order to solicit feedback, particularly from
implementors, with a goal of potential cross-browser implementation
and standardization.
</p>
<p>
This document was published by the <a href="http://www.w3.org/2008/webapps/">Web Applications Working Group</a> as a Working Draft.
If you wish to make comments regarding this document, please send them to
<a href="mailto:public-webapps@w3.org">public-webapps@w3.org</a>
with <code>[ime-api]</code> at the start of the subject header
(<a href="mailto:public-webapps-request@w3.org?subject=subscribe">subscribe</a>,
<a href="http://lists.w3.org/Archives/Public/public-webapps/">archives</a>).
All comments are welcome.
</p>
<p>
Publication as a Working Draft does not imply endorsement by the <abbr title="World Wide Web Consortium">W3C</abbr>
Membership. This is a draft document and may be updated, replaced or obsoleted by other
documents at any time. It is inappropriate to cite this document as other than work in
progress.
</p>
<p>
This document was produced by a group operating under the
<a id="sotd_patent" about="" rel="w3p:patentRules" href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February 2004 <abbr title="World Wide Web Consortium">W3C</abbr> Patent
Policy</a>.
<abbr title="World Wide Web Consortium">W3C</abbr> maintains a <a href="http://www.w3.org/2004/01/pp-impl/42538/status" rel="disclosure">public list of any patent
disclosures</a>
made in connection with the deliverables of the group; that page also includes
instructions for disclosing a patent. An individual who has actual knowledge of a patent
which the individual believes contains
<a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
Claim(s)</a> must disclose the information in accordance with
<a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
6 of the <abbr title="World Wide Web Consortium">W3C</abbr> Patent Policy</a>.
</p>
</section><section id="toc"><h2 class="introductory" aria-level="1" role="heading" id="h2_toc">Table of Contents</h2><ul class="toc" role="directory" id="respecContents"><li class="tocline"><a href="#introduction" class="tocxref"><span class="secno">1. </span>Introduction</a></li><li class="tocline"><a href="#background" class="tocxref"><span class="secno">2. </span>Background: What’s an Input Method Editor?</a><ul class="toc"><li class="tocline"><a href="#composer-section" class="tocxref"><span class="secno">2.1 </span>Composer</a><ul class="toc"><li class="tocline"><a href="#phonetic-composer-section" class="tocxref"><span class="secno">2.1.1 </span>Phonetic Composer</a></li><li class="tocline"><a href="#radical-composer-section" class="tocxref"><span class="secno">2.1.2 </span>Radical Composer</a></li><li class="tocline"><a href="#on-screen-keyboard-section" class="tocxref"><span class="secno">2.1.3 </span>On-Screen Keyboard</a></li></ul></li><li class="tocline"><a href="#converter-section" class="tocxref"><span class="secno">2.2 </span>Converter</a></li></ul></li><li class="tocline"><a href="#conformance" class="tocxref"><span class="secno">3. </span>Conformance</a></li><li class="tocline"><a href="#terminology" class="tocxref"><span class="secno">4. </span>Terminology and Algorithms</a></li><li class="tocline"><a href="#the-inputmethodcontext-property" class="tocxref"><span class="secno">5. </span>The inputMethodContext property</a><ul class="toc"><li class="tocline"><a href="#attributes" class="tocxref"><span class="secno">5.1 </span>Attributes</a></li></ul></li><li class="tocline"><a href="#inputmethodcontext-interface" class="tocxref"><span class="secno">6. </span>The InputMethodContext Interface</a><ul class="toc"><li class="tocline"><a href="#attributes-1" class="tocxref"><span class="secno">6.1 </span>Attributes</a></li><li class="tocline"><a href="#methods" class="tocxref"><span class="secno">6.2 </span>Methods</a></li></ul></li><li class="tocline"><a href="#best-practices" class="tocxref"><span class="secno">7. </span>Best Practices</a><ul class="toc"><li class="tocline"><a href="#life-of-inputmethodcontext" class="tocxref"><span class="secno">7.1 </span>Life of InputMethodContext</a></li></ul></li><li class="tocline"><a href="#acknowledgements" class="tocxref"><span class="secno">8. </span>Acknowledgements</a></li>
<li class="tocline"><a href="#revision-history" class="tocxref"><span class="secno">A. </span>Revision History</a></li>
<li class="tocline"><a href="#references" class="tocxref"><span class="secno">B. </span>References</a><ul class="toc"><li class="tocline"><a href="#normative-references" class="tocxref"><span class="secno">B.1 </span>Normative references</a></li><li class="tocline"><a href="#informative-references" class="tocxref"><span class="secno">B.2 </span>Informative references</a></li></ul></li>
</ul></section>
<section class="informative" id="introduction" typeof="bibo:Chapter" resource="#ref" rel="bibo:Chapter">
<!--OddPage--><h2 aria-level="1" role="heading" id="h2_introduction"><span class="secno">1. </span>Introduction</h2><p><em>This section is non-normative.</em></p>
<p>Even though existing Web-platform APIs allow developers to implement
very complicated Web applications, such as visual chat applications or
WYSIWYG presentation editors, developers have difficulties when
implementing Web applications that involve
<a href="#IME">input-method editors</a>.
To mitigate the difficulties,
<a href="http://www.w3.org/TR/DOM-Level-3-Events/">the DOM
Level 3 Events specification</a>[<cite><a class="bibref" href="#bib-DOM-LEVEL-3-EVENTS">DOM-LEVEL-3-EVENTS</a></cite>]
introduces <i>composition events</i>
to retrieve <a href="#ime-composition">composition text</a>
while it is being composed in an associated IME.</p>
<p>However, Web applications can still run into difficulties
interarcting with IME, such as detecting any UI overlap between
<a href="#candidate-window">IME candidate window</a> and its
underlying UI elements.</p>
<p>To solve the IME-related problems, this specification introduces
an IME API that allows Web applications to interact with the IME.
This specification introduces <a href="#idl-def-InputMethodContext" class="idlType"><code>InputMethodContext</code></a> interface.</p>
<p>There are also proposed standards related to IME:
</p><ul>
<li>Changing IME mode via CSS
(<a href="http://www.w3.org/TR/css3-ui/#ime-mode">ime-mode property
in CSS3 UI</a>)
</li><li>Controlling generic input modality
(<a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/association-of-controls-and-forms.html#input-modalities:-the-inputmode-attribute">inputmode attribute in HTML spec</a>)
</li></ul>
They can work independently of this API.
<p></p>
<p>Please also refer to the separate
<a href="https://dvcs.w3.org/hg/ime-api/raw-file/default/use-cases/Overview.html">use cases for Input Method Editor
API </a>document for more information about possible use cases.</p>
<p>For other possible improvements for interacting with IME, please
refer the <a href="https://dvcs.w3.org/hg/ime-api/raw-file/default/Annex.html">IME API annex</a> document
as a non-normative reference.</p>
<p>Consider the following example.</p>
<p>This example is a simple web search page which gives a user
search query suggestions while the user is doing composition.
This example code hides the suggestion box when IME candidate window
may overlap with it.</p>
<div class="example"><div class="example-title"><span>Example 1</span></div><pre class="example highlight prettyprint" id="ex-ime-suggest-position"><span class="dec"><!DOCTYPE html></span><span class="pln">
</span><span class="tag"><html></span><span class="pln">
</span><span class="tag"><head></span><span class="pln">
</span><span class="tag"><style</span><span class="pln"> </span><span class="atn">type</span><span class="pun">=</span><span class="atv">"text/css"</span><span class="tag">></span><span class="pln">
</span><span class="com">#search0 {</span><span class="pln">
max</span><span class="pun">-</span><span class="pln">width</span><span class="pun">:</span><span class="pln"> </span><span class="lit">400px</span><span class="pun">;</span><span class="pln">
</span><span class="pun">}</span><span class="pln">
</span><span class="com">#input0 {</span><span class="pln">
width</span><span class="pun">:</span><span class="pln"> </span><span class="lit">100</span><span class="pun">%;</span><span class="pln">
</span><span class="pun">}</span><span class="pln">
</span><span class="com">#suggest0 {</span><span class="pln">
width</span><span class="pun">:</span><span class="pln"> </span><span class="lit">100</span><span class="pun">%;</span><span class="pln">
list</span><span class="pun">-</span><span class="pln">style</span><span class="pun">:</span><span class="pln"> none</span><span class="pun">;</span><span class="pln">
margin</span><span class="pun">:</span><span class="pln"> </span><span class="lit">0</span><span class="pun">;</span><span class="pln">
padding</span><span class="pun">:</span><span class="pln"> </span><span class="lit">0</span><span class="pun">;</span><span class="pln">
border</span><span class="pun">-</span><span class="pln">style</span><span class="pun">:</span><span class="pln"> solid</span><span class="pun">;</span><span class="pln">
border</span><span class="pun">-</span><span class="pln">width</span><span class="pun">:</span><span class="pln"> </span><span class="lit">1px</span><span class="pun">;</span><span class="pln">
border</span><span class="pun">-</span><span class="pln">color</span><span class="pun">:</span><span class="pln"> </span><span class="com">#000;</span><span class="pln">
</span><span class="pun">}</span><span class="pln">
</span><span class="tag"></style></span><span class="pln">
</span><span class="tag"><script</span><span class="pln"> </span><span class="atn">language</span><span class="pun">=</span><span class="atv">"javascript"</span><span class="pln"> </span><span class="atn">type</span><span class="pun">=</span><span class="atv">"text/javascript"</span><span class="tag">></span><span class="pln">
</span><span class="kwd">function</span><span class="pln"> init</span><span class="pun">()</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
</span><span class="kwd">var</span><span class="pln"> node </span><span class="pun">=</span><span class="pln"> document</span><span class="pun">.</span><span class="pln">getElementById</span><span class="pun">(</span><span class="str">'input0'</span><span class="pun">);</span><span class="pln">
</span><span class="com">// This code only handles the compositionupdate event for brevity of the</span><span class="pln">
</span><span class="com">// example, but of course other input field changes should also be handled.</span><span class="pln">
node</span><span class="pun">.</span><span class="pln">addEventListener</span><span class="pun">(</span><span class="str">'compositionupdate'</span><span class="pun">,</span><span class="pln"> onCompositionUpdate</span><span class="pun">,</span><span class="pln"> </span><span class="kwd">false</span><span class="pun">);</span><span class="pln">
</span><span class="com">// Register handlers for candidate window appearance change.</span><span class="pln">
</span><span class="kwd">var</span><span class="pln"> ctx </span><span class="pun">=</span><span class="pln"> node</span><span class="pun">.</span><span class="pln">inputMethodContext</span><span class="pun">;</span><span class="pln">
ctx</span><span class="pun">.</span><span class="pln">addEventListener</span><span class="pun">(</span><span class="str">'candidatewindowshow'</span><span class="pun">,</span><span class="pln"> onCandidateWindowShow</span><span class="pun">,</span><span class="pln"> </span><span class="kwd">false</span><span class="pun">);</span><span class="pln">
ctx</span><span class="pun">.</span><span class="pln">addEventListener</span><span class="pun">(</span><span class="str">'candidatewindowhide'</span><span class="pun">,</span><span class="pln"> onCandidateWindowHide</span><span class="pun">,</span><span class="pln"> </span><span class="kwd">false</span><span class="pun">);</span><span class="pln">
</span><span class="pun">}</span><span class="pln">
</span><span class="com">// Sends an XHR request to get search suggestions.</span><span class="pln">
</span><span class="com">// Upon receiving the result, expandSuggest() is called back.</span><span class="pln">
</span><span class="kwd">function</span><span class="pln"> getSuggests</span><span class="pun">(</span><span class="pln">query</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
</span><span class="com">// For brevity, implementation of this function is omitted.</span><span class="pln">
</span><span class="pun">}</span><span class="pln">
</span><span class="kwd">function</span><span class="pln"> expandSuggest</span><span class="pun">(</span><span class="pln">candidates</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
</span><span class="com">// Callback after getting search suggestions.</span><span class="pln">
</span><span class="kwd">var</span><span class="pln"> suggest </span><span class="pun">=</span><span class="pln"> document</span><span class="pun">.</span><span class="pln">getElementById</span><span class="pun">(</span><span class="str">'suggest0'</span><span class="pun">);</span><span class="pln">
</span><span class="kwd">var</span><span class="pln"> i</span><span class="pun">;</span><span class="pln">
</span><span class="com">// Clear old suggestions.</span><span class="pln">
</span><span class="kwd">for</span><span class="pln"> </span><span class="pun">(</span><span class="pln">i </span><span class="pun">=</span><span class="pln"> </span><span class="lit">0</span><span class="pun">;</span><span class="pln"> i </span><span class="pun"><</span><span class="pln"> suggest</span><span class="pun">.</span><span class="pln">childNodes</span><span class="pun">.</span><span class="pln">length</span><span class="pun">;</span><span class="pln"> i</span><span class="pun">++)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
suggest</span><span class="pun">.</span><span class="pln">removeChild</span><span class="pun">(</span><span class="pln">suggest</span><span class="pun">.</span><span class="pln">childNodes</span><span class="pun">[</span><span class="lit">0</span><span class="pun">]);</span><span class="pln">
</span><span class="pun">}</span><span class="pln">
</span><span class="com">// Render new suggeston list.</span><span class="pln">
</span><span class="kwd">for</span><span class="pln"> </span><span class="pun">(</span><span class="pln">i </span><span class="pun">=</span><span class="pln"> </span><span class="lit">0</span><span class="pun">;</span><span class="pln"> i </span><span class="pun"><</span><span class="pln"> candidates</span><span class="pun">.</span><span class="pln">length</span><span class="pun">;</span><span class="pln"> i</span><span class="pun">++)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
suggest</span><span class="pun">.</span><span class="pln">appendChild</span><span class="pun">(</span><span class="pln">document</span><span class="pun">.</span><span class="pln">createElement</span><span class="pun">(</span><span class="str">'li'</span><span class="pun">));</span><span class="pln">
suggest</span><span class="pun">.</span><span class="pln">childNodes</span><span class="pun">[</span><span class="pln">i</span><span class="pun">].</span><span class="pln">textContent </span><span class="pun">=</span><span class="pln"> candidates</span><span class="pun">[</span><span class="pln">i</span><span class="pun">];</span><span class="pln">
</span><span class="pun">}</span><span class="pln">
</span><span class="pun">}</span><span class="pln">
</span><span class="kwd">function</span><span class="pln"> onCompositionUpdate</span><span class="pun">(</span><span class="pln">event</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
</span><span class="kwd">var</span><span class="pln"> query </span><span class="pun">=</span><span class="pln"> document</span><span class="pun">.</span><span class="pln">getElementById</span><span class="pun">(</span><span class="str">'input0'</span><span class="pun">).</span><span class="pln">value</span><span class="pun">;</span><span class="pln">
getSuggests</span><span class="pun">(</span><span class="pln">query</span><span class="pun">);</span><span class="pln">
</span><span class="pun">}</span><span class="pln">
</span><span class="com">// Hides suggest window once IME candidate window is shown.</span><span class="pln">
</span><span class="kwd">function</span><span class="pln"> onCandidateWindowShow</span><span class="pun">(</span><span class="pln">event</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
</span><span class="kwd">var</span><span class="pln"> suggest </span><span class="pun">=</span><span class="pln"> document</span><span class="pun">.</span><span class="pln">getElementById</span><span class="pun">(</span><span class="str">'suggest0'</span><span class="pun">);</span><span class="pln">
suggest</span><span class="pun">.</span><span class="pln">style</span><span class="pun">.</span><span class="pln">display </span><span class="pun">=</span><span class="pln"> </span><span class="str">'none'</span><span class="pun">;</span><span class="pln">
</span><span class="pun">}</span><span class="pln">
</span><span class="com">// Unhides suggest window once IME candidate window is closed.</span><span class="pln">
</span><span class="kwd">function</span><span class="pln"> onCandidateWindowHide</span><span class="pun">(</span><span class="pln">event</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
</span><span class="kwd">var</span><span class="pln"> suggest </span><span class="pun">=</span><span class="pln"> document</span><span class="pun">.</span><span class="pln">getElementById</span><span class="pun">(</span><span class="str">'suggest0'</span><span class="pun">);</span><span class="pln">
suggest</span><span class="pun">.</span><span class="pln">style</span><span class="pun">.</span><span class="pln">display </span><span class="pun">=</span><span class="pln"> </span><span class="str">''</span><span class="pun">;</span><span class="pln">
</span><span class="pun">}</span><span class="pln">
</span><span class="tag"></script></span><span class="pln">
</span><span class="tag"></head></span><span class="pln">
</span><span class="tag"><body></span><span class="pln">
</span><span class="tag"><div</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"search0"</span><span class="tag">></span><span class="pln">
</span><span class="tag"><input</span><span class="pln"> </span><span class="atn">type</span><span class="pun">=</span><span class="atv">"text"</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"input0"</span><span class="pln"> </span><span class="atn">placeholder</span><span class="pun">=</span><span class="atv">"search here"</span><span class="tag">></span><span class="pln">
</span><span class="tag"><ul</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"suggest0"</span><span class="tag">></ul></span><span class="pln">
</span><span class="tag"></div></span><span class="pln">
</span><span class="tag"></body></span><span class="pln">
</span><span class="tag"></html></span></pre></div>
</section>
<section class="informative" id="background" typeof="bibo:Chapter" resource="#ref" rel="bibo:Chapter">
<!--OddPage--><h2 aria-level="1" role="heading" id="h2_background"><span class="secno">2. </span>Background: What’s an Input Method Editor?</h2><p><em>This section is non-normative.</em></p>
<p>An <dfn id="IME">IME</dfn> (input-method editor) is an application
that allows a standard keyboard (such as a US-101 keyboard) to be used
to type characters and symbols that are not directly represented on the
keyboard itself. In China, Japan, and Korea, IMEs are used ubiquitously
to enable standard keyboards to be employed to type the very large
number of characters required for writing in Chinese, Japanese, and
Korean.</p>
<p>On platforms with touch-based input device such as mobile phones,
an IME also plays a role to type text that a simple on-screen keyboard
cannot type directly.</p>
<p>A <dfn id="system-ime">system IME</dfn> is an IME already installed
on a user's system.
</p><p>An IME consists of two modules; a <a href="#composer">composer</a>
and a <a href="#converter">converter</a>.</p>
<p>A <dfn id="composer">composer</dfn> is a context-free parser that
composes non-ASCII characters (including phonetic characters) from
keystrokes, e.g. Hiragana or Pinyin.</p>
<p>A <dfn id="converter">converter</dfn> is a context-sensitive parser
that looks up a dictionary to convert phonetic characters to
a set of ideographic characters, e.g. Kanji.</p>
<p>An <dfn id="ime-clause">IME clause</dfn> is a grammatical word
produced in an IME.</p>
<p>An <dfn id="ime-selected-clause">IME selected clause</dfn> is an
<a href="#ime-clause">IME clause</a> currently being converted by
an IME.</p>
<p>An <dfn id="ime-composition">IME composition</dfn>
is an instance of text produced in an IME. For IMEs that can produce
multiple words, an IME composition consists of multiple IME clauses.
For IMEs that produce only one word, an IME composition is equal to an
IME clause.</p>
<p>When an IME receives keystrokes, it sends the keystrokes to a
composer and receives phonetic characters matching to the keystrokes.
When an IME receives phonetic characters from a composer, it sends the
phonetic characters to a converter and receives the list of ideographic
characters matching to the phonetic characters. The following figure
shows the basic structure of an IME.</p>
<figure id="fig-ime-structure">
<p><img height="199" src="TR3_files/image10.png" width="615"></p>
<figcaption>Fig. <span class="figno">1</span> <span class="fig-title">Basic structure of an IME</span></figcaption>
</figure>
<section id="composer-section" typeof="bibo:Chapter" resource="#ref" rel="bibo:Chapter">
<h3 aria-level="2" role="heading" id="h3_composer-section"><span class="secno">2.1 </span>Composer</h3>
<p>A composer consists of two types of composers: a
<a href="#phonetic-composer">phonetic composer</a>
and a
<a href="#radical-composer">radical composer</a>.</p>
<p>A <dfn id="phonetic-composer">phonetic composer</dfn> composes a phonetic
character from its ASCII representation.</p>
<p>A <dfn id="radical-composer">radical composer</dfn> composes a
phonetic character from <a href="#phonetic-radical">phonetic radicals</a>.</p>
<p>A <dfn id="phonetic-radical">phonetic radical</dfn> is a character
component of a Latin character, a Chinese character, or a Korean
character. A Latin character can consist of an ASCII character and
accent marks, e.g. the character ‘á’ consists of
the ASCII character ‘a’ and the accent mark
‘´’. A Chinese character can consist of Chinese
character components that refer to its semantic origins, e.g. the
Chinese character ‘略’ consists of two components
‘田’ and ‘各’. A Korean
character consists of Korean character components that represent
consonants or vowels, e.g. the Korean character
‘가’ consists of the consonant
‘ㄱ’ and the vowel ‘ㅏ’.</p>
<p>A <dfn id="composition-window">composition window</dfn> is a window
that shows ASCII characters being composed by
<a href="#phonetic-composer">phonetic composers</a> or
<a href="#phonetic-radical">phonetic radicals</a> being composed by
<a href="#radical-composer">radical composers</a>.</p>
<p>An IME usually shows the text being composed by a composer with its
own style to distinguish it from the existing text. Even though most
of composers output phonetic characters, some composers (such as
Bopomofo composers) output a placeholder character
instead of phonetic characters while composing text.</p>
<section id="phonetic-composer-section" typeof="bibo:Chapter" resource="#ref" rel="bibo:Chapter">
<h4 aria-level="3" role="heading" id="h4_phonetic-composer-section"><span class="secno">2.1.1 </span>Phonetic Composer</h4>
<p>Phonetic composers are not only used for typing Simplified
Chinese and Japanese, but also used for typing non-ASCII
characters (such as mathematical symbols, Yi, Amharic, etc.) with
a US-101 keyboard. Each of these languages has a mapping table
from its character to a sequence of ASCII characters representing
its pronunciation: e.g.,
‘か’ to ‘ka’ in Japanese, and;
‘卡’ to ‘ka’ in Simplified Chinese.
This mapping table is called as Romaji for Japanese and Pinyin for
Simplified Chinese, respectively. A phonetic composer uses these
mapping tables to compose a phonetic character from a sequence of
ASCII characters produced by a US keyboard.</p>
<p>An example of a phonetic composer for Simplified Chinese outputs
the ASCII characters that were input by the user, as its
composition text.</p>
<figure id="fig-ascii-composition-text">
<p><img height="180" src="TR3_files/image11.png" width="352"></p>
<figcaption>Fig. <span class="figno">2</span> <span class="fig-title">Composition text (Simplified Chinese)</span></figcaption>
</figure>
<p>On the other hand, a typical phonetic composer for Japanese
outputs phonetic characters when the typed ASCII characters have
corresponding phonetic characters.</p>
<figure id="fig-kana-composition-text">
<p><img height="180" src="TR3_files/image13.png" width="352"></p>
<figcaption>Fig. <span class="figno">3</span> <span class="fig-title">Composition text (Japanese)</span></figcaption>
</figure>
<p>An example of a phonetic composer for mathematical symbols
outputs composed mathematical symbol and shows the source
keystrokes in its own window, which is an example of a composition
window.</p>
<figure id="fig-composition-window">
<p><img height="214" src="TR3_files/image14.png" width="435"></p>
<figcaption>Fig. <span class="figno">4</span> <span class="fig-title">Composition text (Latex input)</span></figcaption>
</figure>
</section>
<section id="radical-composer-section" typeof="bibo:Chapter" resource="#ref" rel="bibo:Chapter">
<h4 aria-level="3" role="heading" id="h4_radical-composer-section"><span class="secno">2.1.2 </span>Radical Composer</h4>
<p>Radical composers are mainly used for typing Traditional
Chinese and Korean with phonetic keyboards. Each phonetic
keyboard of these languages can produce phonetic radicals:
e.g., typing ‘r’ produces ‘ㄱ’
on a Korean keyboard; typing ‘o’ produces
‘人’ on a Traditional-Chinese (or Bopomofo)
keyboard, etc. A radical composer composes a phonetic
character from phonetic radicals given by these keyboards:
e.g., typing ‘ㄱ’ (r) and ‘ㅏ’
(k) produces ‘가’ on a Korean keyboard;
typing ‘人’ (o), ‘弓’ (n), and
‘火’ (f) produces ‘你’ on a
Traditional-Chinese keyboard, etc.</p>
<p>A radical composer for Korean outputs the phonetic radicals as
its composition text.</p>
<figure id="fig-radical-composer-korean">
<p><img height="180" src="TR3_files/image15.png" width="352"></p>
<figcaption>Fig. <span class="figno">5</span> <span class="fig-title">Radical composer (Korean)</span></figcaption>
</figure>
<p>A radical composer for Traditional Chinese outputs a
placeholder character (U+3000) and shows the phonetic radicals
being composed to its own window. This window is an example
of a composition window.</p>
<figure id="fig-radical-composer-chinese">
<p><img height="180" src="TR3_files/image02.png" width="352"></p>
<figcaption>Fig. <span class="figno">6</span> <span class="fig-title">Radical composer (Traditional Chinese)</span></figcaption>
</figure>
<p>Some platforms (such as Mac and Linux) use radical composers
for typing accented characters used in European countries.
For example,
typing ‘ ̈ ’ (option+u) and ‘a’ (a)
produces ‘ä’ on US keyboards of Mac.</p>
<figure id="fig-radical-composer-mac">
<p><img height="177" src="TR3_files/image01.png" width="479"></p>
<figcaption>Fig. <span class="figno">7</span> <span class="fig-title">Radical composer (Mac)</span></figcaption>
</figure>
</section>
<section id="on-screen-keyboard-section" typeof="bibo:Chapter" resource="#ref" rel="bibo:Chapter">
<h4 aria-level="3" role="heading" id="h4_on-screen-keyboard-section"><span class="secno">2.1.3 </span>On-Screen Keyboard</h4>
<p>On touch-based platforms without hardware keyboard like
mobile phone or tablet platforms, some kind of on-screen keyboard
is displayed to help a user typing text, which occupies some
part of the screen. A user uses this keyboard to type composition
text.</p>
<figure id="fig-on-screen-keyboard-english">
<p><img height="557" src="TR3_files/mobile_ime_keyboard_en.png" width="416"></p>
<figcaption>Fig. <span class="figno">8</span> <span class="fig-title">An example of an on-screen keyboard (English)</span></figcaption>
</figure>
<p>The layout of an on-screen keyboard may vary depending on
language or its input modality (e.g. a telephone number
input field requires number buttons only).</p>
<figure id="fig-on-screen-keyboard-japanese">
<p><img height="467" src="TR3_files/mobile_ime_keyboard_jp.png" width="416"></p>
<figcaption>Fig. <span class="figno">9</span> <span class="fig-title">An example of an on-screen keyboard (Japanese)</span></figcaption>
</figure>
</section>
</section>
<section id="converter-section" typeof="bibo:Chapter" resource="#ref" rel="bibo:Chapter">
<h3 aria-level="2" role="heading" id="h3_converter-section"><span class="secno">2.2 </span>Converter</h3>
<p>A converter is a context-sensitive parser used for replacing
the outputs of a composer to ideographic characters on Chinese,
Japanese, and Korean.</p>
<div class="note"><div class="note-title" aria-level="3" role="heading" id="h_note_1"><span>Note</span></div><p class="">Korean seldom uses ideographic characters.</p></div>
<p>Because Chinese, Japanese, and Korean have many homonyms, each
sequence of phonetic characters usually matches many ideographic
characters: e.g., a Japanese
phonetic character ‘か’ matches Japanese
ideographic characters
‘化’, ‘科’,
‘課’,
etc.; Pinyin characters ‘ka’ matches Simplified-Chinese
ideographic characters ‘卡’,
‘喀’,
‘咯’, etc.; Bopomofo characters
‘人弓’ matches Traditional-Chinese
ideographic characters ‘乞’,
‘亿’, ‘亇’, etc.</p>
<p>A converter looks up a dictionary and shows a list of
candidates of possible ideographic characters so a user can choose
one. This list is known as a <dfn id="candidate-list">candidate
list</dfn>.
A candidate list is known as a <dfn id="candidate-window">candidate
window</dfn> when it has its own window.</p>
<p>Some Japanese IMEs show annotations in its
<a href="#candidate-window">candidate window</a>
for a character that is not so easy to distinguish from other
characters (such as full-width alphabets, full-width Katakanas,
and half-width Katakanas, etc.), as shown in the following
figure.</p>
<figure id="fig-candidate-window-japanese">
<p><img height="342" src="TR3_files/image05.png" width="393"></p>
<figcaption>Fig. <span class="figno">10</span> <span class="fig-title">Candidate window (Japanese)</span></figcaption>
</figure>
<p>The next figure shows a <a href="#candidate-window">candidate
window</a> of a Simplified-Chinese IME.</p>
<figure id="fig-candidate-window-simplified-chinese">
<p><img height="308" src="TR3_files/image04.png" width="390"></p>
<figcaption>Fig. <span class="figno">11</span> <span class="fig-title">Candidate window (Simplified Chinese)</span></figcaption>
</figure>
<p>And the next figure shows a <a href="#candidate-window">candidate
window</a> of a Traditional-Chinese IME.</p>
<figure id="fig-candidate-window-traditional-chinese">
<p><img height="180" src="TR3_files/image06.png" width="352"></p>
<figcaption>Fig. <span class="figno">12</span> <span class="fig-title">Candidate window (Traditional Chinese)</span></figcaption>
</figure>
<p>Some techniques are used to improve conversion quality.
For example, a converter integrates an <dfn id="MRU">MRU</dfn>
(Most-Recently Used) list.
Even though there are many ideographic characters for each phonetic
character (or phonetic radical), a user does not usually use all
these ideographic characters. A converter uses an
<a href="#MRU">MRU list</a> to filter out ideographic characters not
used so often from a <a href="#candidate-list">candidate list</a>.
Another example is a grammar parser. A converter that
integrates a grammar parser splits the given phonetic characters
into grammatical clauses and converts only one clause at a time.
When a sequence of phonetic characters consists of n clauses and the
i-th clause has m_i candidates, the total number of the candidates
for the input characters becomes (m_1 * m_2 * … * m_n).
To reduce the number of candidates owned by a converter,
a converter usually processes one clause at a time. This clause is
called the <dfn id="selected-clause">selected clause</dfn>.</p>
<p>An IME usually renders a <a href="#selected-clause">selected
clause</a> with a special style to distinguish it from other
clauses, as shown in the following figure.</p>
<figure id="fig-selected-clause">
<p><img height="346" src="TR3_files/image08.png" width="394"></p>
<figcaption>Fig. <span class="figno">13</span> <span class="fig-title">Selected clause (Japanese)</span></figcaption>
</figure>
<p>When a converter converts two or more clauses, it chooses
candidates for the selected clause so it becomes grammatically
consistent with the surrounding clauses:
e.g., Japanese converters usually output
‘危機一髪’ (not
‘危機一発’)
for Japanese phonetic characters
‘ききいっぱつ’
because
‘危機一発’ is grammatically