Requirement 12029: local role for link

["Eliot Kimber" <ekimber@innodata-isogen.com>]

All links have at least two ends and being able to provide a role for 
one end requires that you be able to specify the role for the other end. 
It doesn't matter how the ends are addressed (that is, whether an end is 
addressed explicitly or implicitly).

Thus, the fact that the link element has a role= attribute that 
specifies the role of the *target* topic means that there needs to be a 
way to specify the role of the *local* topic (the topic that contains 
the link).

The use case in my original submission is illustrative of the 
requirement, where the links reflect aspects of the objects the topics 
are documenting, in the case of UML types, the types themselves.

In UML, types can be related together in arbitrary ways, with each end 
of a given relation being given a different label. These labels 
translate directly the to the role value on the DITA link element. 
However, with the current design of the link element, you can only 
express one of these two labels, the label for the target type (topic).

The application of topics to UML types is by no means unique: any 
specialization that tries to reflect a real-world data model or modeling 
language will likely have the same need for arbitrarily-labeled 
relationships among topics, relationships that have no particular 
relationship to the built-in role values currently provided for link.

Another indicator that a local role is required is that, when 
constructed using reltables in a map, it is possible to provide 
arbitrary role values for each of the ends of a link. However, without 
some way to express the local role value, there is no way to reflect all 
the roles when the reltable links are translated into links within 
individual topics.  This means that there is information loss when going 
from reltables to embedded links.

Cheers,

Eliot
-- 
W. Eliot Kimber
Professional Services
Innodata Isogen
8500 N. Mopac, Suite 402
Austin, TX 78759
(214) 954-5198

ekimber@innodata-isogen.com
www.innodata-isogen.com