When a topic requires cross-references to other topics where those cross-references will always be valid in the context of the topic, they should be contained within a related-links section after the topic body. In all other cases, cross-references should be defined in the relationship table of the ditamap.
There are three methods through which links can be included in DITA content:
The most effective method for most documents is the relationship table approach. However, if the cross-references will always be appropriate for the topic, regardless of the context in which it is used, then the related-links section can be used.
The related-links section is technically metadata, and is structured within the topic but outside the body section. It is made up of link elements, which are similar in function to an xref element.