An application can accomplish many tasks by parsing or modifying a small subset of the document.

Three features of the OpenXML format cooperate to provide this modularity.

  • A document is not monolithic; it is built out of multiple parts.

  • Relationships between parts are themselves stored in parts.

  • The ZIP archive format that is typically used to support OpenXML documents supports random access to each part.

For example:

  • An application could move a slide cleanly from one presentation to another, together with resources such as images and layouts, entirely without parsing slide content (§3:13.3.8). This example uses data called explicit relationships to find the slide and its resources. Explicit relationships are defined by the Open Packaging Conventions and can be parsed without any knowledge of PresentationML tag semantics (§1:9.2, §2:8.3).

  • An application could strip all of the comments from a WordprocessingML document without parsing any of its contents (§1:11.3.2). This example uses data called implicit relationships to find the comments. Implicit relationships are OpenXML-specific and therefore do require some knowledge of the relevant markup language (§1:9.2).