Dr.Ken Lunde
For those who are not aware, IVSes (Ideographic Variation Sequences) are a standardized Unicode mechanism for representing otherwise unencoded variant forms of CJK Unified Ideographs using “plain text,” specifically via a sequence of a Base Character (aka, a CJK Unified Ideograph) followed by a Variation Selector (one of the 240 in Plane 14). This sequence maps to a glyph that corresponds to a registered IVS, which is part of a registered IVD (Ideographic Variation Database) Collection.
An excellent example is U+8FBB (辻) for which two glyphs are used in Japan, both of which are included in the Adobe-Japan1-6 character collection. The JIS90 (aka, JIS X 0208-1990) glyph is specified with the following IVS: <U+8FBB,U+E0100>. The JIS2004 (aka, JIS X 0213:2004) glyphs is specified with the following IVS: <U+8FBB,U+E0101>. The attached screen shots show both forms in a “plain text” environment, in Adobe Acrobat 9.0 and in the Mac OS X 10.6 “Text Edit” application. To date, the only registered IVD Collection is Adobe-Japan1, which corresponds to the Adobe-Japan1-6 character collection. This is significant, because almost all OpenType Japanese fonts are based on the Adobe-Japan1-x character collection, and its latest version, Adobe-Japan1-6, includes well over 1,000 unencoded glyphs that correspond to CJK Unified Ideographs. These are supported via IVSes.
If we consider the software components that are required for supporting IVSes, there are three primary ones, specifically fonts, applications, and input methods. Let’s briefly explore them.
Fonts were the first component to be IVS-enabled, through the specification and inclusion of the Format 14 ‘cmap’ subtable. Our AFDKO (Adobe Font Development Kit for OpenType) includes tools, such as makeotf and spot, that support the building and proofing of IVS-enable OpenType fonts. DTL OTMaster is a third-party font development utility that is also IVS-enabled. To date, we have built nearly fifty IVS-enabled OpenType Japanese fonts. In other words, IVS-enabled OpenType Japanese fonts are not in short supply. Instead, they are abundant.
The first applications to be IVS-enabled were Adobe Acrobat 9.0 and Adobe Reader 9.0 (in the context of PDF Forms), Adobe InDesign CS4, and Flash Player 10.0. The first OSes to be IVS-enabled were Mac OS X Version 10.6 and Windows 7, both of which were released during the latter half of 2009. An IVS-enabled OS is critical because it provides other applications with the necessary APIs to effectively become IVS-enabled. The fact that the two major OSes are now IVS-enabled is an important event.
While the extent to which IVSes are supported in applications and OSes still needs to be expanded and enhanced, such as for searching operations, specifically the option to ignore the Variation Selector portion of the IVS, there is still one missing component, which is an IVS-enabled input method. JustSystems is developing an IVS-enabled version of their ATOK input method, and given the steps that Apple and Microsoft have taken to IVS-enable the latest iterations of their respective OSes, it makes sense that they will eventually IVS-enable the bundled input methods. The ability to emit IVSes from an input method is a critical part of the workflow, and is clearly a missing component.
In other words, and in summary, a lot of progress has been made with regard to IVS support, but a lot of work remains to be done.
IVS支持：当前状态和后续工作
English
有些人并不知道 IVSes (Ideographic Variation Sequences 异体字序列，后文简称IVS) 是一标准Unicode构造，用于纯文本状态下显示CJK Unified Ideographs(中日韩表意字符)之外的无编码异体字形，具体格式是一基本字符（亦是中日韩表意字符）后面紧随一个异体选择符（Unicode第14平面中240个异体选择符中的一个），该序列对应到一个已注册的异体字，是已注册IVD(异体字数据库)集合中的一部分。
举一个关于 U+8FBB (辻) 的例子，在日文中该字包含两个字形，并且它们都属于Adobe-Japan1-6字符集，JIS90（亦称JIS X 0208-1990）字形用IVS具体表示就是<U+8FBB,U+E0100>，JIS2004 （亦称JIS X 0213:2004）字形的IVS表达是<U+8FBB,U+E0101>，下面的图显示了这两个字形分别在Adobe Acrobat 9.0 和 Mac OS X 10.6 “Text Edit” 的纯文本状态。到目前为止，唯一注册的IVD 集合是Adobe-Japan1，与其对应的是Adobe-Japan1-6 字符集。这有很大的意义，因为几乎所有的日文OpenType 字库都基于Adobe-Japan1-x字符集，并且最新版本Adobe-Japan1-6包含了1,000多个CJK 统一表意字符的无编码字形，这些都是通过异体字序列来实现的。
如果我们细数一下支持IVSes必需的软件组件，有三个基本要素，专门的字库、应用程序和输入法，下面让我们简单地探究一下吧。
凭借详细的规划和Format 14 ‘cmap’ 子表中的规定，字库成为第一个支持IVS的组件。我们的AFDKO (Adobe Font Development Kit for OpenType) 所包含的工具，比如makeotf 和 spot支持创建、校对 IVS特性的OpenType 字库。DTL OTMaster 是第三方字库开发工具，也支持IVS。 到目前为止，我们已经制作了接近50种IVS特性的日文OpenType字库，换句话说， 支持IVS的日文OpenType字库不是很少而是很多。
第一个支持IVS的软件是Adobe Acrobat 9.0 和 Adobe Reader 9.0 (在编辑PDF 表格内容时支持IVS)，Adobe InDesign CS4和Flash Player 10.0。第一个支持IVS的系统是Mac OS X Version 10.6 和 Windows 7，它们都发布于2009后半年。支持IVS的系统是关键的组件，因为它能给其他程序提供必要的API去有效地支持IVS，两个主要系统现已支持IVS是个重要的进展。
在应用程序和系统中支持IVSes的程度仍然需要不断扩展提高，比如搜索操作，特别是忽略IVS中异体选择符的选项。 目前仍然有一个遗漏的组件，那便是支持IVS的输入法。JustSystems正在开发他们的ATOK输入法IVS版本以支持异体字输入，下一步就是苹果和微软公司将输入法载入他们各自最新支持IVS的系统，最终捆绑支持IVS的输入法是非常有意义的。有能力从输入法触发IVSes是工作流中重要的一环节，这显然是目前缺失的一个组件。
总而言之，关于IVS 的支持已有很多进展，但仍有很多工作尚待完成。
延伸阅读：
Unicode Technical Standard #37：Unicode Ideographic Variation Database
OpenType specification: Cmap Format 14: Unicode Variation Sequences
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