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DITA map files
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.
Relationship between hierarchy and relationship table links
Links can be generated into output formats during publishing based on hierarchical and relationship table relationships in the ditamap. Regardless of the source, the links are merged during publishing.

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.
  - Hierarchical linking relationships
    The hierarchical relationship of topic references in the ditamap can be used to generate links from parent topics to child topics, from child topics to parent topics, and between child topics.
  - Relationship between hierarchy and relationship table links
    Links can be generated into output formats during publishing based on hierarchical and relationship table relationships in the ditamap. Regardless of the source, the links are merged during publishing.
  - Collection types
    The collection-type attribute of the topicref element defines the relationship between any nested topic references within a ditamap. Changing the collection type affects the way in which automatic links and topic previews are generated when the ditamap is processed to an output format.
  - The linking attribute
    The linking attribute of the topicref and relcell elements in the ditamap is used to specify the way in which links are generated during publishing.
  - Breadcrumbs
    Breadcrumb trails are navigation tools used in some online document formats, and can be automatically generated from DITA source.
- 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 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.

Relationship between hierarchy and relationship table links

Links can be generated into output formats during publishing based on hierarchical and relationship table relationships in the ditamap. Regardless of the source, the links are merged during publishing.

Cross-reference links are automatically generated by DITA publishing tools based on the hierarchical relationships in the ditamap, and on relationship table associations in the reltable section of the ditamap. In addition, links can be manually specified in an individual topic in the related-links section of the topic.

Regardless of which linking methodology was used, the resultant links in the output are merged into categorised link blocks at the end of the topic in the output.

Figure 1 shows a sample of links at the bottom of a topic in Microsoft HTML Help output. The Parent topic: link is based on the hierarchy; it is a link to the parent of the current topic. The first two Related concepts links are based on the ditamap hierarchy, as the parent topic has its collection-type attribute set to family. (This specifies that all sibling topics should be linked together.) The third link is a manual link specified in the related-links section of the current topic. These three links are all concept information types, and that's why they have been grouped under the Related concepts heading. The two Related tasks links are generated from a relationship in the reltable, again, grouped together because both topics are task information types.

Screen capture showing a mixture of hierarchy, reltable and related links — Figure 1. How hierarchy, reltable and related links are merged in the output topic

The key features of the ditamap that would generate the output in Figure 1 are:


...
<topicref collection-type="family" href="c_Engine_Options.dita" type="concept">
   <topicref href="ej20.xml" type="concept"/>
   <topicref href="ej25.xml" type="concept"/>
   <topicref href="ej25_turbo.xml" type="concept"/>
</topicref>
...
<reltable>
   <relrow>
     <relcell>
       <topicref format="dita" href="ej25_turbo.xml" type="concept"/>
     </relcell>
     <relcell>
       <topicref format="dita" href="start_xrw.xml" type="task"/>
      	<topicref format="dita" href="start_lumberer.xml" type="task"/>
     </relcell>
   </relrow> 
</reltable>