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 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.



These models represent only the default document types distributed by OASIS. Actual content models will differ with each new document type.
Doctype Content model
subjectScheme ( (data or data-about or subjectdef or topicref or (anchorref or keydef or mapref or topicgroup or topichead or topicset or topicsetref) ) (any number) )

Contained by

Doctype Content model
subjectScheme subjectScheme


- 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"/>
  <!-- ... -->


Name Description Data Type Default Value Required?
navtitle Specifies the title of the topic as it will appear in the navigation or tables of contents that are generated from the map. Beginning with DITA 1.2, the preferred way to specify the navigation title in a map is with the navtitle element, available inside the topicmeta element. CDATA #IMPLIED No
href 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. CDATA #IMPLIED No
keys Introduces one or more global identifiers for a resource referenced from a map. See The keys attribute for details on how to use the keys attribute. NMTOKEN #IMPLIED No
processing-role Describes the processing role of the referenced topic. The processing default is "normal". If the value is not specified locally, but is specified on an ancestor, the value will cascade from the closest ancestor.
Normal topic that is a readable part of the information.
The topic is used as a resource for processing purposes, but is not a readable unit of information on its own. This topic should not be included in a rendered table of contents, and the topic should not be rendered on its own.
See Using the -dita-use-conref-target value for more information.
(normal | resource-only | -dita-use-​conref-​target) #IMPLIED No
query This attribute is deprecated. It may be removed in the future. CDATA #IMPLIED No
collection-type Collection types describe how links relate to each other.
Indicates that the order of the child topics is not significant.
Indicates that the order of the child topics is significant; output processors will typically link between them in order.
Indicates that one of the children should be selected.
Represents a tight grouping in which each of the referenced topics not only relates to the current topic but also relate to each other.
See Using the -dita-use-conref-target value for more information.
(unordered | sequence | choice | family | -dita-use-​conref-​target) family No
type Describes the target of a reference. See The type attribute for detailed information on supported values and processing implications. CDATA #IMPLIED No
scope The scope attribute identifies the closeness of the relationship between the current document and the target resource. See The scope attribute for more information on values. (local | peer | external | -dita-use-​conref-​target) #IMPLIED No
format The format attribute identifies the format of the resource being referenced. See The format attribute for details on supported values. CDATA #IMPLIED No
linking Defines some specific linking characteristics of a topic's current location in the map.
A topic can only be linked to and cannot link to other topics.
A topic cannot be linked to but can link to other topics.
A topic can be linked to and can link to other topics. Use this to override the linking value of a parent topic.
A topic cannot be linked to or link to other topics.
See Using the -dita-use-conref-target value for more information.
(targetonly | sourceonly | normal | none | -dita-use-​conref-​target) normal No
univ-atts attribute group (includes select-atts, id-atts, and localization-atts groups) A set of related attributes, described in univ-atts attribute group
global-atts attribute group (xtrf, xtrc) A set of related attributes, described in global-atts attribute group
class, outputclass, keyref Keyref provides a redirectable reference based on a key defined within a map. See The keyref attribute for information on using this attribute. Class and outputclass are described in Other common DITA attributes

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