Using keys for addressing
Syntax
For references to topics, maps, and non-DITA resources, the value of the
               @keyref attribute is simply a key name (for example,
               keyref="topic-key"). 
            
For references to non-topic elements within topics,
               the value of the @keyref attribute is a key name, a slash ("/"), and the ID of the target element (for
               example, keyref="topic-key/some-element-id".)
            
Example
For example, consider this topic in the document file.dita:
               
<topic id="topicid"> <title>Example referenced topic</title> <body> <section id="section-01">Some content.</section> </body> </topic>and this key definition:
<map>
  <topicref keys="myexample"
    href="file.dita"
  />
</map>
            
            A cross reference of the form keyref="myexample/section-01" resolves
               to the <section> element in the topic. The key reference is
               equivalent to the URI reference
               xref="file.dita#topicid/section-01".