= Cross-References in Trac =

As Trac is a little bit more than a Wiki, 
its backlinks are a little bit more powerful than traditional
backlinks... 
Therefore we should rather talk about ''cross-references''.

A cross-reference is a link from a Trac object (the ''source'')
to another Trac object (the ''destination'').

Usually, such links are created after processing some Wiki text
attached to the source object (a ''facet'' of that object).

Here's the current list of Trac objects that can reference
each other, along with their facets:
 * Wiki page 
   * content facet
   * attachment comment facets
 * Ticket 
   * summary facet
   * description facet
   * comments facets
   * attachment comment facets
   * (more to come...)
 * Changeset 
   * log message facet
 * Report 
   * title facet
   * description facet
 * Milestone 
   * title facet
   * description facet
 * Source 
   * (no facet, only as a target)

A cross-reference is also called a ''relation'' if a specific semantic is
attached to the link from the source object to the destination object.
If there's no relation defined, one simply knowns that the two objects
are somehow related, like for traditional backlinks
(however, for a backlink, Trac will also show the text that surrounds
the link in the source Wiki text).

Those relations can be used to fulfill many needs. 
The ticket dependencies feature is one example.


----

== Implementation Notes ==

The [source:branches/cboos-dev/xref-branch xref] branch
currently contains an implementation for it, and work
is in progress to adapt it for trunk integration
(any comments welcomed, of course).

See also: 
 * The original enhancement request ticket: #1242
 * Backlink support: #611 and #646
 * Relationship and ticket dependencies support: #31 and #226