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DITA map files
DITA map vocabulary
The navref element
The navref element is a specialist element used when constructing dynamically-merged modular Help systems.

Introduction
Information types and topics
Topics are the building blocks of modular documents, and organising topics by semantic information types is one of the architectural features of DITA.
DITA map files
- Purpose of ditamap files
  DITA map files are used for defining the topics of a publication, specifying the topic sequence, and controlling linking between topics.
- Topic manifest
  Any topics referenced anywhere in the ditamap will be processed into the output publication.
- Topic hierarchy
  In DITA, the sequence and hierarchy of the topics to be published are defined in the ditamap through nested topicref elements.
- Relationship tables
  Relationship tables are used to store linking relationships between topics in a collection in the ditamap, rather than in individual topics. Linking relationships are defined in a table-like structure, with rows in the table determining which topics are linked to which.
- Linking relationships
  DITA encourages the linking relationships to be stored outside the topic content. Links can be generated from topic hierarchies, relationship tables, and related-links section links.
- Inheritance and cascades in ditamaps
  Properties in ditamaps sometimes cascade from parent elements to child elements. Some values in ditamaps also override the equivalent values in referenced topics.
- Embedded (or nested) ditamaps
  The technique of using embedded, or nested, ditamaps can make it easier to manage documents by separating complex collections of topics into a number of smaller, simpler collections.
- DITA map vocabulary
  - The topicref element
    The basic building block of ditamap files is the topic reference (topicref) element.
  - The href attribute in a topic references
    A topic reference (topicref) in a ditamap references the topic (or other resource) to be included in the output publication through the href attribute. The value of the href attribute must conform to the standard URI format.
  - The topichead element
    The topichead element in the ditamap provides a title-only node in the hierarchy, into which normal topic references are nested. Although technically valid, this element should not be used because it results in inconsistent output.
  - The navref element
    The navref element is a specialist element used when constructing dynamically-merged modular Help systems.
  - The copy-to attribute
    The copy-to attribute of the topicref element is used in the unusual situation where you need to create two copies of the same topic in the output, and to link to each copy of the output topic separately. The value of the attribute is the file name of the duplicate.
  - The chunk attribute
    The chunk attribute can control the way output files are generated during the publishing process. Most chunk attribute values apply only to composite topics, which should be avoided. The to-content value is used to generate a single output topic from multiple DITA source topics.
  - Non-DITA topic references
    A ditamap can include references to non-DITA resources, such as PDF documents, spreadsheet files, presentation files, online tutorials, HTML files, and Internet addresses. The topicref element is used for these references, with format and scope attributes describing the type of resource.
  - Dangling topicrefs
    If a ditamap includes a reference to a topic that does not exist, the publishing process will generate output with a broken link. It will not gracefully omit the reference. You should therefore take care to avoid these dangling topicref.
- The bookmap feature
  Bookmaps are a specialisation of the base DITA map information type. Like ditamaps, bookmaps are containers for structure and context metadata, and do not contain any content. Bookmaps are used to describe page layout publishing outputs such as books, articles, manuals and research papers. They contain information structures that are specific to linear publications, such as tables of figures, title pages, chapters, sections and parts.
Syntax and mark-up
Language and punctuation
Graphics and figures
Cross-referencing
Cross-references are a means of binding individual topics into a coherent and navigable document.
Content re-use
Metadata, conditional processing, and indexing
The DITA documentation process
DITA authoring concepts
Moving from style-based authoring to a structured authoring methodology such as DITA requires a radically different approach to writing.

The navref element

The navref element is a specialist element used when constructing dynamically-merged modular Help systems.

Some Help system output formats, including Eclipse Help and Microsoft HTML Help, support runtime merging of modular Help files, where a master Help system incorporates slave Help system modules dynamically when the user opens the Help.

The navref element provides for run-time modular navigation structures. In other words, the target defined by navref is resolved not when the parent ditamap is being built, but when the resultant deliverable is being rendered. It is a fairly obscure element, and is not commonly used.

You may choose to use navref as a placeholder when you are building a document suite, where a constituent ditamap is not yet available. Even though the navref href is not available, the ditamap will still build. When the map referenced by the navref is available, the navref should be replaced by a normal topicref.