(map subjectScheme) This differs from topicref-atts-no-toc only by providing a default for @processing-role A subjectScheme is a specialized DITA map that defines a collection of controlled values rather than a collection of topics. A <schemeref> element provides a reference to another scheme. Typically, the referenced scheme defines a base set of controlled values extended by the current scheme. The values in the referenced scheme are merged with the current scheme; the result is equivalent to specifying all of the values in a single map. For subjects within the <hasNarrower> element, the container subject is more general than each of the contained subjects. That is, this element makes the default hierarchical relationship explicit, although the way in which a relationship is narrower is not specified. Specifies that the contained hierarchy expresses KIND-OF relationships between subjects. The <hasPart> element specifies that the contained hierarchy expresses PART-OF relationships between subjects. Specifies that the contained hierarchy expresses INSTANCE-OF relationships between subjects. In an INSTANCE-OF hierarchy, the child subject is a specific entity or object and the parent subject is a type, kind, or class of entity or object. For example, New York City is a specific instance of a city. The <hasRelated> element identifies an associative relationship between the container subject and each of the contained subjects. Default removed for DITA 1.3. The <subjectdef> element defines a subject (also known as a controlled value) within a scheme. To make the subject easy to identify, a <subjectdef> may use a keys attribute to assign a key to the subject. A subject with a key can be identified elsewhere with a keyref. The <subjectdef> may use a navtitle element or attribute to supply a label for the subject. The <subjectdef> may also refer to a topic that captures the consensus definition for the subject. If a <subjectdef> refers to a topic, the <subjectdef> must also have the locktitle attribute set to &#34;yes&#34; in order to use the navtitle instead of the topic title to label the subject. The <subjectHead> element provides a heading for a group of subjects. The subjectHead element itself does not reference a file and cannot be referenced as a key, so it does not define any controlled values. The <subjectHeadMeta> element allows a navigation title and short description to be associated with a subject heading. The <enumerationdef> element identifies one attribute and one or more categories that contain the controlled values for the enumeration. The type attribute has a default value of keys. The <elementdef> element identifies an element on which an attribute is enumerated. When the <elementdef> is left out of an <enumerationdef> element, the enumeration is bound to the attribute in all elements. The <attributedef> element defines an attribute as an enumeration by specifying controlled values from a scheme. The <defaultSubject> element is used within an attribute enumeration to set the default value for that attribute in cases where no value is specified on the attribute. The default subject must be one of the controlled values within the categories specified for the attribute. 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). To define roles within a relationship, you can specialize the relatedSubjects container and its contained subjectdef elements, possibly setting the linking attribute to targetonly or sourceonly. For instance, a dependency relationship could contain depended-on and dependent subjects. The <subjectRelTable> element is a specialized relationship table which establishes relationships between the subjects in different columns of the same row. Where there are many instances of a subject relationship in which different subjects have defined roles within the relationship, you can use or specialize the subjectRelTable. Note that each row matrixes relationships across columns such that a subject receives relationships to every subject in other columns within the same row. The <subjectRelHeader> element specifies the roles played by subjects in associations. The role definition can be an informal navtitle or a formal reference The <subjectRel> element contains a set of subjects that are related in some manner. Each group of subjects is contained in a <subjectRole> element; the associations between different columns in the same row are evaluated in the same way as those in a <relrow> (from which <subjectRel> is specialized) but define relationships between the subjects instead of links between topic documents. The <subjectRole> element contains a set of subjects that are related to other subjects in the same row of the current <subjectRelTable>. By default, no relationship is defined between multiple subjects in the same <subjectRole> element.