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附录 E（规范性）PDF 名称注册表

Annex E (normative) PDF Name Registry

E.1 概述

E.1 General

本附录讨论了一个供开发者使用的注册表，该注册表由国际标准化组织（ISO）管控，目前由奥多比（Adobe）代表ISO提供。注册表包含私有名称和格式，兼容的写入器可以使用这些内容。开发者前缀应用于标识对PDF的扩展，这些扩展使用一级名称（见下文），并且供公众使用。（见7.12.2，“开发者扩展字典”。）这里的“开发者”指任何实体，包括个人、公司、非营利组织、标准机构、开源团体等，他们正在开发标准或软件以使用和扩展ISO 32000 - 1。

可以向PDF文档添加私有数据，使兼容的阅读器能够根据这些数据改变行为。同时，无论使用哪种兼容的阅读器，用户在打开PDF文档时都有一定的预期。为了满足这些预期，PDF对私有数据施加了某些限制。

兼容的写入器或兼容的阅读器可以定义新类型的动作、目标位置、注释、安全和文件系统处理程序。如果用户使用不支持新类型对象的兼容阅读器打开PDF文档，兼容的阅读器应按照附录I中的描述运行。

兼容的写入器还可以向任何作为字典实现的PDF对象添加键，但文件尾部字典除外（见7.5.5，“文件尾部”）。此外，兼容的写入器可以创建标记，以指示标记内容操作符的角色（PDF 1.2），如14.6，“标记内容”中所述 。

This annex discusses a registry for developers, controlled by ISO and currently provided by Adobe on behalf of ISO. The registry contains private names and formats that may be used by conforming writers. Developer prefixes shall be used to identify extensions to PDF that use First Class names (see below) and that are intended for public use. (See 7.12.2, “Developer Extensions Dictionary.) “Developers” means any entity including individuals, companies, non-profits, standards bodies, open source groups, etc., who are developing standards or software to use and extend ISO 32000-1.

Private data may be added to PDF documents that enable conforming reader’s to change behavior based on this data. At the same time, users have certain expectations when opening a PDF document, no matter which conforming reader is being used. PDF enforces certain restrictions on private data in order to meet these expectations.

A conforming writer or conforming reader may define new types of actions, destinations, annotations, security, and file system handlers. If a user opens a PDF document using a conforming reader for which the new type of object is not supported, the conforming reader shall behave as described in Annex I.

A conforming writer may also add keys to any PDF object that is implemented as a dictionary, except the file trailer dictionary (see 7.5.5, "File Trailer"). In addition, a conforming writer may create tags that indicate the role of marked-content operators (PDF 1.2), as described in 14.6, "Marked Content".

E.2 名称注册表

E.2 Name Registry

为避免与第三方名称以及PDF未来版本产生冲突，国际标准化组织（ISO）维护着一个针对某些私有名称和格式的注册表。开发者只能添加符合注册表规则的私有数据。该注册表分为三类：

  • 一类：对广大开发者有价值的名称和数据格式。ISO 32000规范中定义的所有名称均为一类名称。公开可用的兼容阅读器应将其私有数据用于一类名称。一类名称和数据格式需向ISO注册，并应提供给所有开发者使用。若要将私有名称和格式作为一类提交以供审核，请访问以下网页查看有关注册私有PDF扩展的链接：

    http://adobe.com/go/ISO32000Registry

    数据格式描述应遵循ISO 32000 - 1的风格，并完整说明扩展信息的预期功能。

  • 二类：适用于特定开发者的名称。ISO不注册二类数据格式。ISO通过注册开发者特定的4字节前缀来分发二类名称。这些字节后面跟一个下划线（5Fh），应作为开发者添加的所有私有数据名称的首字符。ISO不会将相同的前缀注册给两个不同的开发者，从而确保不同开发者的二类名称不会冲突。开发者有责任避免以冲突的方式使用相同的名称。若要注册开发者特定的前缀，请访问以下网页：

    http://adobe.com/go/ISO32000Registry

  • 三类：仅在PDF文件中使用的名称，由于可能与其他方定义的三类名称冲突，其他第三方永远不会看到这些文件。三类名称都必须以专门为私有扩展保留的特定前缀开头。该前缀为XX，应作为开发者添加的所有私有数据名称的首字符。注册三类名称无需联系ISO。

文档信息字典（见14.3.3，“文档信息字典”）或线索信息字典（在线索字典的I条目中；见12.4.3节，“文章”）的新键不得注册。

有关开发者前缀、处理程序以及对ISO 32000 - 1扩展的更多信息，请访问http://www.aiim.org/ISO32000Registry 。

To avoid conflicts with third-party names and with future versions of PDF, ISO maintains a registry for certain private names and formats. Developers shall only add private data that conforms to the registry rules. The registry includes three classes:

  • First class. Names and data formats that are of value to a wide range of developers. All names defined in this ISO 32000 specification are first-class names. Conforming readers that are publicly available shall use first-class names for their private data. First-class names and data formats shall be registered with ISO and shall be made available for all developers to use. To submit a private name and format for consideration as first-class, see the link on registering a private PDF extension, at the following Web page:

http://adobe.com/go/ISO32000Registry

Data format descriptions shall follow the style of ISO 32000-1 and give a complete specification of the intended function of the extended information.

  • Second class. Names that are applicable to a specific developer. ISO does not register second-class data formats.) ISO distributes second-class names by registering developer-specific 4-byte prefixes. Those bytes followed by a LOW LINE (5Fh) shall be used as the first characters in the names of all private data added by the developer. ISO shall not register the same prefix to two different developers, thereby ensuring that different developers’ second-class names shall not conflict. It is the responsibility of the developer not to use the same name in conflicting ways. To register a developer-specific prefix, use the following Web page:

http://adobe.com/go/ISO32000Registry

  • Third class. Names that may be used only in PDF files that other third parties will never see because they can conflict with third-class names defined by others. Third-class names shall all begin with a specific prefix reserved for private extensions. This prefix, which is XX, shall be used as the first characters in the names of all private data added by the developer. It is not necessary to contact ISO to register third-class names.

New keys for the document information dictionary (see 14.3.3, "Document Information Dictionary") or a thread information dictionary (in the I entry of a thread dictionary; see Section 12.4.3, “Articles”) shall not be registered.

More information about developer prefixes, handlers and extensions to ISO 32000-1 can be obtained at http:// www.aiim.org/ISO32000Registry.