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Metadata, conditional processing, and indexing
Indexing
DITA incorporates powerful features for indexing, including multi-level indexing, and see and see-also redirection. Index entries can be applied in the ditamap, in the topic prolog, and inline within the topic content.
Index see and see also
Readers can be re-directed from a searched-for term to related terms in the index that provide further references. You can use the index-see and index-see-also indexing elements for this purpose.

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
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
- Conditional processing concepts
  When DITA content is processed to a reading format, rules to exclude or highlight some of the content can be defined in a ditaval file. This conditional processing requires metadata attributes to be set on DITA elements that may possibly be excluded or highlighted.
- Condition (or select) attributes
  The audience, platform, product, otherprops and rev attributes can be applied to most DITA elements. They are used for conditional processing, and are known as the condition (or select) attributes.
- Filtering and flagging
  Content marked with metadata attributes can be conditionally processed so that the content is filtered (excluded) or flagged (highlighted) in the published output.
- Other metadata
  In addition to the select attributes, DITA content includes many forms of metadata. These metadata elements and attributes are used to manage and organise topics, ditamaps and publications.
- Indexing
  DITA incorporates powerful features for indexing, including multi-level indexing, and see and see-also redirection. Index entries can be applied in the ditamap, in the topic prolog, and inline within the topic content.
  - Placement of indexterm elements
    The indexterm element is pure metadata, and does not display. You should place index entries in the prolog section of the topic, or in the topicmeta section of the topicref in the ditamap only if the term is specific to a particular publication.
  - Nesting index entries
    The technique of nesting indexterm elements can produce multi-level indexes in output documents.
  - Index see and see also
    Readers can be re-directed from a searched-for term to related terms in the index that provide further references. You can use the index-see and index-see-also indexing elements for this purpose.
  - Re-using index entries
    You can create a special ditamap which has a sole purpose of being the container for common indexterm elements for re-use in the prolog section of topics (and the topicmeta section of ditamaps, if required) through the conref feature.
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.

Index see and see also

Readers can be re-directed from a searched-for term to related terms in the index that provide further references. You can use the index-see and index-see-also indexing elements for this purpose.

The index-see element is used to redirect the reader to a synonymous index term. The index-see element is nested inside a standard indexterm element, with indexterm containing the term to appear in the index, and the index-see containing the term for readers to be pointed to. The index-see must be the only child element of the parent indexterm.

For example, the code

<indexterm>forced induction
   <index-see>turbocharger</index-see>
</indexentry>

will result in an output of:

forced induction, See turbocharger

Where possible, index-see entries should be placed in the ditamap topicmeta, because they are logically applicable at the publication level, rather than the topic level.

The structure of the index-see entry in the ditamap is shown in the example:

<map id="lumberer_om_05">
  <title>Lumberer XT Owner's Manual</title>
  <topicmeta>
    <keywords>
      <indexterm>forced induction
        <index-see>turbocharger</index-see>
      </indexterm>
    </keywords>
  </topicmeta>
  <topicref...>...</topicref>
  <topicref...>...</topicref>
  <topicref...>...</topicref>
		...
</map>

The index-see-also element is similar in function to index-see, except that it also provides a page reference to the original term.

For example, the code

<indexterm>forced induction
   <index-see-also>turbocharger</index-see-also>
</indexentry>

will result in an output of:

forced induction .................... 15
See also turbocharger

Do not use index-see-also in the ditamap top level map element's topicmeta, although you can use it within the topicref element's topicmeta within the ditamap.

In a hypertext document that supports indexes, the same example might be displayed as: