A <schemeref> element references another subject scheme map. Typically, the referenced subject scheme defines a base set of controlled values; the referencing map then extends the base set of controlled values. The values specified in the subject scheme maps are merged; the result is equivalent to specifying all of the values in a single map.

Content models

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


- map/topicref subjectScheme/schemeref


The following attributes are available on this element: Universal attribute group, Link relationship attribute group (with narrowed definitions of @href, @format, and @type, given below), @navtitle and @query from Topicref element attributes group, @outputclass, @keys, and @keyref.

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 @format attribute sets a default value of "ditamap", because the purpose of the element is to reference a ditamap document. Otherwise, the attribute is the same as described in Link relationship attribute group.
Describes the target of a reference. For the <schemeref> element, this value defaults to "scheme", because the element is expected to point to another subject scheme.

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