Processing xrefs and conrefs within a conref

When referenced content contains a content reference or cross reference, the effective target of the reference depends on the form of address that is used in the referenced content. It also might depend on the map context, especially when key scopes are present.

Direct URI reference (but not a same-topic fragment identifier ): When the address is a direct URI reference of any form other than a same-topic fragment identifier, processors MUST resolve it relative to the source document that contains the original URI reference.
Same-topic fragment identifier: When the address is a same-topic fragment identifier, processors MUST resolve it relative to the location of the content reference (referencing context).
Key reference: When the address is a key reference, processors MUST resolve it relative to the location of the content reference (referencing context).

When resolving key references or same-topic fragment identifiers, the phrase location of the content reference means the final resolved context. For example, in a case where content references are chained (topic A pulls from topic B, which in turn pulls a reference from topic C), the reference is resolved relative to the topic that is rendered. When topic B is rendered, the reference is resolved relative to the content reference in topic B; when topic A is rendered, the reference is resolved relative to topic A. If content is pushed from topic A to topic B to topic C, then the same-topic fragment identifier is resolved in the context of topic C.

The implication is that a content reference or cross reference can resolve to different targets in different use contexts. This is because a URI reference that contains a same-topic fragment identifier is resolved in the context of the topic that contains the content reference, and a key reference is resolved in the context of the key scope that is in effect for each use of the topic that contains the content reference.

Note: In the case of same-topic fragment identifiers, it is the responsibility of the author of the content reference to ensure that any element IDs that are specified in same-topic fragment identifiers in the referenced content will also be available in the referencing topic at resolution time.

Example: Resolving conrefs to elements that contain cross references

Consider the following paragraphs in paras-01.dita that are intended to be used by reference from other topics:

<topic id="paras-01"><title>Reusable paragraphs</title>
    <body>
        <p id="p1">See <xref href="#paras-01/p5"/>.</p>
        <p id="p2">See <xref href="topic-02.dita#topic02/fig-01"/>.</p>
        <p id="p3">See <xref href="#./p5"/>.</p>
        <p id="p4">See <xref keyref="task-remove-cover"/>.</p>
        <p id="p5">Paragraph 5 in paras-01.</p>
    </body>
</topic>

The paragraphs are used by content reference from other topics, including the using-topic-01.dita topic:

<topic id="using-topic-01"><title>Using topic one</title>
    <body>
        <p id="A" conref="paras-01.dita#paras-01/p1"/> 
        <p id="B" conref="paras-01.dita#paras-01/p2"/> 
        <p id="C" conref="paras-01.dita#paras-01/p3"/>
        <p id="D" conref="paras-01.dita#paras-01/p4"/>
        <p id="p5">Paragraph 5 in using-topic-01</p>  
    </body>
</topic>

Following resolution of the content references and processing of the <xref> elements in the referenced paragraphs, the rendered cross references in using-topic-01.dita are shown in the following table.

Paragraph	Value of `@id` attribute on conrefed paragraph	`<xref>` within conrefed paragraph	Resolution
A	p1	`<xref href="#paras-01/p5"/>`	The cross reference in paragraph p1 is a direct URI reference that does not contain a same-topic fragment identifier. It can be resolved only to paragraph p5 in paras-01.dita, which contains the content "Paragraph 5 in paras-01".
B	p2	`<xref href="topic-02.dita#topic02/fig-01"/>`	The cross reference in paragraph p2 is a direct URI reference. It can be resolved only to the element with `id="fig-01"` in topic-02.dita.
C	p3	`<xref href="#./p5"/>`	The cross reference in paragraph p3 is a direct URI reference that contains a same-topic fragment identifier. Because the URI reference contains a same-topic fragment identifier, the reference is resolved in the context of the referencing topic (using-topic-01.dita). If using-topic-01.dita did not contain an element with `id="p5"`, then the conref to paragraph p3 would result in a link resolution failure.
D	p4	`<xref keyref="task-remove-cover"/>`	The cross reference in paragraph p4 is a key reference. It is resolved to whatever resource is bound to the key name "task-remove-cover" in the applicable map context.

Example: Resolving conrefs to elements that contain key-based cross references

Consider the following map, which uses the topics from the previous example:

<map>
  <topicgroup keyscope="product-1">
    <topicref keys="task-remove-cover" href="prod-1-task-remove-cover.dita"/>
    <topicref href="using-topic-01.dita"/>
  </topicgroup>
  <topicgroup keyscope="product-2">
    <topicref keys="task-remove-cover" href="prod-2-task-remove-cover.dita"/>
    <topicref href="using-topic-01.dita"/>
  </topicgroup>
</map>

The map establishes two key scopes: "product-1" and "product-2". Within the map branches, the key name "task-remove-cover" is bound to a different topic. The topic using-topic-01.dita, which includes a conref to a paragraph that includes a cross reference to the key name "task-remove-cover", is also referenced in each branch. When each branch is rendered, the target of the cross reference is different.

In the first branch with the key scope set to "product-1", the cross reference from paragraph p4 is resolved to prod-1-task-remove-cover.dita. In the second branch with the key scope set to "product-2", the cross reference from paragraph p4 is resolved to prod-2-task-remove-cover.dita.