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DITA map files
Topic hierarchy
In DITA, the sequence and hierarchy of the topics to be published are defined in the ditamap through nested topicref elements.
Creating a Glossary of Terms
A Glossary of Terms is defined in a ditamap using either standard topicref elements to glossary entry topics, or using glossref elements (introduced in DITA 1.2).

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.
  - Designing a topic hierarchy
    A well-designed topic hierarchy will make the reader's task of finding information in a publication easier.
  - Heading levels and ditamaps
    The topic hierarchy in the ditamap is used to generate heading levels and styles in page layout outputs.
  - Controlling the top node (default topic)
    DITA publishing tools sometimes process the hierarchy of a ditamap slightly differently for different target output formats. A workaround can be used to achieve greater consistency between different outputs to avoid confusing readers.
  - Excluding topics from the output TOC
    When generating an output which includes a TOC, you may want to generate a topic from your ditamap but not have it appear in the output TOC. This is achieved through the toc and linking attributes of the topicref.
  - Creating a Glossary of Terms
    A Glossary of Terms is defined in a ditamap using either standard topicref elements to glossary entry topics, or using glossref elements (introduced in DITA 1.2).
- 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 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.

Creating a Glossary of Terms

A Glossary of Terms is defined in a ditamap using either standard topicref elements to glossary entry topics, or using glossref elements (introduced in DITA 1.2).

A Glossary of Terms is made up of multiple small glossentry topics, each with a structure of a term (glossterm) element followed by a definition (glossdef) element. The glossary of terms is assembled by referencing all the glossentry topics in a ditamap.

In DITA 1.2, instead of using the standard topicref element to reference the glossentry topics, you can use the glossref element. The glossref element is specialised from the topicref element, but differs in having a mandatory keys attribute.

The keys attribute is used for the automatic generation of links from terms in topic text to the corresponding glossary definition. The links are indirect links, in that the term in the topic links to a key, and the target of that key is defined in the ditamap. (This method of linking is known as indirection.)

The following code sample compares a topicref and a glossref:

<topicref href="mechanical/g_abs_brake_system.dita" />

<glossref  href="mechanical/g_brake_system.dita" keys="abs" />

To specify that a link to be generated from a term to the glossary definition during publishing, you must use a term element, or specialised form of the term element named abbreviated-form. Both term and abbreviated-form elements have a keyref attribute, which is the reference to the corresponding key in the ditamap glossref element. (The keyref attribute was introduced in DITA 1.2.)

For example, to specify a link from the acronym ABS to a glossary definition of ABS Brake System, the following code could be used:

<p>Your car has <abbreviated-form keyref="abs"/>.

Except for small documents, using a separate ditamap for the glossary of terms, and then embedding the glossary ditamap in the main ditamap for the collection, is the architecture most easy to manage.