14.1 概述¶
14.1 General
本条款中描述的功能不会影响文档的最终外观。而是这些功能使文档能够包含更高级的信息，以便在符合标准的产品之间进行文档交换：
- 过程集（14.2，“过程集”），用于定义 PDF 操作符的实现
- 元数据（14.3，“元数据”），包含有关文档或文档组件的一般信息，例如标题、作者、创建和修改日期
- 文件标识符（14.4，“文件标识符”），用于可靠地从一个 PDF 文件引用另一个 PDF 文件
- 页面片段字典（14.5，“页面片段字典”），允许符合标准的产品在 PDF 文档中嵌入私有数据以供自身使用
- 标记内容操作符（14.6，“标记内容”），用于标识内容流的部分，并将其与附加属性或外部指定对象关联
- 逻辑结构功能（14.7，“逻辑结构”），用于在文档内容上施加层次结构组织
- 标记 PDF（14.8，“标记 PDF”），一组使用标记内容和逻辑结构功能的约定，以便提取和重用文档内容用于其他用途
- 提高文档对残障用户可访问性的各种方法（14.9，“可访问性支持”），包括标识其书写的自然语言（如英语或西班牙语），以便文本转语音引擎使用
- Web 捕获扩展（14.10，“Web 捕获”），用于从互联网或本地存储的 HTML、PDF、GIF、JPEG 和 ASCII 文本文件创建 PDF 文件
- 支持印前生产工作流的功能（14.11，“印前支持”），如页面边界的指定以及打印标记、颜色分色、输出意图、陷印和高分辨率图像的低分辨率代理的生成
The features described in this clause do not affect the final appearance of a document. Rather, these features enable a document to include higher-level information that is useful for the interchange of documents among conforming products:
- Procedure sets (14.2, “Procedure Sets”) that define the implementation of PDF operators
- Metadata (14.3, “Metadata”) consisting of general information about a document or a component of a document, such as its title, author, and creation and modification dates
- File identifiers (14.4, “File Identifiers”) for reliable reference from one PDF file to another
- Page-piece dictionaries (14.5, “Page-Piece Dictionaries”) allowing a conforming product to embed private data in a PDF document for its own use
- Marked-content operators (14.6, “Marked Content”) for identifying portions of a content stream and associating them with additional properties or externally specified objects
- Logical structure facilities (14.7, “Logical Structure”) for imposing a hierarchical organization on the content of a document
- Tagged PDF (14.8, “Tagged PDF”), a set of conventions for using the marked content and logical structure facilities to facilitate the extraction and reuse of a document’s content for other purposes
- Various ways of increasing the accessibility of a document to users with disabilities (14.9, “Accessibility Support”), including the identification of the natural language in which it is written (such as English or Spanish) for the benefit of a text-to-speech engine
- The Web Capture extension (14.10, “ Web Capture”), which creates PDF files from Internet-based or locally resident HTML, PDF, GIF, JPEG, and ASCII text files
- Facilities supporting prepress production workflows (14.11, “Prepress Support”), such as the specification of page boundaries and the generation of printer’s marks, colour separations, output intents, traps, and low-resolution proxies for high-resolution images