The <relatedSubjects> element establishes associative relationships between each child subject and every other child subject (unless the association is restricted by the @linking attribute of the subjects).

For filtering and flagging, processors need only inspect the subordinate hierarchies under category subjects that are bound to attributes. Filtering and flagging processors do not have to understand specific types of relationships. Explicit relationships are useful primarily for information viewers with advanced capabilities.

The content provider can identify the relationship by specifying a @keys attribute, label the relationship by specifying a <navtitle> element or @navtitle attribute, and provide a consensus definition of the relationship including by referencing a topic. If the relationship has an identifying key, the content provider can use the @keyref attribute to specify the same relationship for different subjects.

Content models

See appendix for information about this element in OASIS document type shells.


- map/topicref subjectScheme/relatedSubjects


The following scheme establishes that the Linux, the Apache Web Server, and the MySQL Database are related:

  <!-- ... -->
    <subjectdef keys="linux"     navtitle="Linux"/>
    <subjectdef keys="apacheweb" navtitle="Apache Web Server"/>
    <subjectdef keys="mysql"     navtitle="MySQL Database"/>
  <!-- ... -->


The following attributes are available on this element: Universal attribute group, Link relationship attribute group (with a narrowed definition of @href, given below), @navtitle and @query from Topicref element attributes group, @outputclass, @keys, and @keyref. This element also uses @processing-role, @collection-type, and a narrowed definition of @linking (given below) from Attributes common to many map elements.

A pointer to the resource represented by the <topicref>. See The @href attribute for detailed information on supported values and processing implications. References to DITA content cannot be below the topic level: that is, you cannot reference individual elements inside a topic. References to content other than DITA topics should use the @format attribute to identify the kind of resource being referenced.
On this element, the @linking attribute has a default value of "normal". Otherwise, the attribute is the same as defined in Attributes common to many map elements.

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