Using the -dita-use-conref-target value
Ordinarily, when an element uses @conref, any other attributes specified locally will be preserved when the reference is resolved. This causes problems when attributes are required, because required attributes must be specified regardless of whether the @conref attribute is present. The purpose of the -dita-use-conref-target value is to allow the author to specify a value for a required attribute while still allowing the conref resolution process to use the matching attribute from the referenced element. The value has the same result when the attribute is not required.
The -dita-use-conref-target token is allowed on any attribute where it is not prohibited by the XML grammar files or by the specification. For example, while @cols on the <tgroup> element is defined as being a number, this token is implicitly allowed in order to support conref processing for <tgroup>. However, the token is not allowed for the @id attribute on the <topic> element, because "-dita-use-conref-target" does not fit the syntax required by the XML grammar files.
This example shows a map where the <topichead> element uses @conref. It specifies the @navtitle attribute as well as the @toc attribute. In the resolved element, @navtitle from the referencing element is not preserved because it uses -dita-use-conref-target. The @toc attribute from the referencing element overrides the @toc attribute on the referenced element using normal conref resolution rules.
Note
Pre-resolution
<map><title>Conref demonstration</title>
<topichead id="heading"
navtitle="This is a heading"
toc="yes"
linking="normal">
<topicref href="topic.dita" navtitle="content"/>
</topichead>
<topichead conref="#heading"
navtitle="-dita-use-conref-target"
toc="no">
</topichead>
</map>Effective result post-resolution
<map><title>Conref demonstration</title>
<topichead id="heading"
navtitle="This is a heading"
toc="yes"
linking="normal">
<topicref href="topic.dita" navtitle="content"/>
</topichead>
<topichead navtitle="This is a heading"
toc="no"
linking="normal">
<topicref href="topic.dita" navtitle="content"/>
</topichead>
</map>