Knowledge is not gained by collecting
information, but by understanding what information to throw away.
John Durham Peters
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.
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.
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.