Additional Details on Intent or Implications of Topicrefs in Relcolspec

[Eliot Kimber <ekimber@contrext.com>]

I'm writing a lesson on relationship tables and thus doing a fresh close
reading of the reltable language reference entries.

The <relcolspec> element can contain zero or more topicrefs. The 1.2 spec
language says:

"Beginning with DITA 1.2, you also can add <topicref> elements to the
<relcolspec> element; this defines a
relationship between the topics that are referenced in the <recolspec>
element and the topics that are
referenced in the column of the relationship table."

It also defines rules for using any navigation title or referenced topic
title as the title for column (if no <title> element is present).

My question: what was intended by "a relationship" in the paragraph above?
Was there any specific type of relationship that was intended beyond
simply providing a column label? I don't recall any of the discussion that
must have gone into this addition in 1.2 (either because I wasn't involved
or because it was so long ago).

My guess is that the intent was that linked topics are in a "type of"
relationship with the relcell entries for the column, e.g., if I have a
topicref to the topic title "Subtask" that explains what a subtask is,
then it is establishing that topics referenced from that column are
instances of the type "subtask" in the context of the relationship table.

But the 1.2 language certainly doesn't limit you to that interpretation.
For example, there could be an implication for some navigation
relationship or something.

I don't think we need to limit the type of relationship that can be
implied in this case but I think we need to add some commentary that
either reflects the original intent or provides some typical use cases and
what a presentation or behavior effect might be beyond simply setting the
column label. The example in the 1.2 spec shows using a topicref and says
there's a relationship, but doesn't say what the relationship means or
what presentation or behavior implications it might have beyond providing
the title.

Also, the language as written seems to assume that there is at most one
topicref in the relcolspec, but relcolspec allows zero or more. The
obvious rule is that the first topicref provides the title if there's no
<title> element, but the spec doesn't say that now. (I'm actually
surprised that Jarno hasn't noticed that--maybe he hasn't had to touch the
relationship table processing recently.)

In the first edition of my book I just use topicheads in relcell, this
emphasizes the title-setting aspect. But looking at it now, it would make
more sense to just use <title> in that case.

Cheers,

E.

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Eliot Kimber, Owner
Contrext, LLC
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