Norm Reconsiders DITA Specialization
This is very significant and I eagerly await Norm's thoughts.
As Norm relates in his post, he and I had what I thought was a very productive discussion about specialization and what it could mean in a DocBook context. I think Norm characterized my position accurately, namely that the essential difference between DocBook and DITA is specialization and that makes DITA better.
Here by "better" I mean "better value for the type of applications to which DITA and DocBook are applied". It's a better value because:
1. Specialization enables blind interchange, which I think is very important, if not of utmost importance, even if that interchange is only with your future self.
2. Specialization lowers the cost of implementing new markup vocabularies (that is, custom markup for a specific use community) roughly an order of magnitude easier.
There's more to it than that, of course, but that's the key bits.
All the other aspects of DITA that people see as distinguishing: modularity, maps, conref, etc., could all be replicated in DocBook.
If we assume that DITA's more sophisticated features like maps and keyref and so forth are no more complicated than they need to be to meet requirements, then the best that DocBook could do is implement the exact equivalent of those features, which is fine. So to that degree, DocBook and DITA are (or could be) functionally equivalent in terms of specific markup features. (But note that any statement to the effect that "DITA's features are too complicated" reflects a lack of understanding of the requirements are that DITA satisfies--I can assure you that there is no aspect of DITA that is not used and depended on by at least one significant user community. That is, any attempt, for example, to add a map-like facility to DocBook that does not reflect all the functional aspects of DITA maps will simply fail to satisfy the requirements of a significant set of potential users.)
But note that currently DocBook and DITA are *not* functionally equivalent: DocBook lacks a number of important features needed to support modularity and reuse. But I don't consider that important. What really matters is specialization.
Note also that I'm not necessarily suggesting that DocBook adapt the DITA specialization mechanism exactly as it's formulated in DITA. I'm suggesting that DocBook needs the functional equivalent of DITA's specialization facility.
Note also that DocBook as currently formulated at a content model level probably cannot be made to satisfy the constraints specialization requires in terms of consistency of structural patterns along a specialization hierarchy and probably lacks a number of content model options that you'd want to have in order to support reasonable specializations from a given base.
But those are design problems that could be fixed in a DocBook V6 or something if it was important or useful to do so.
Finally, note that in DITA 2.0 there is the expectation that the specialization facility will be reengineered from scratch. That would be the ideal opportunity to work jointly to develop a specialization mechanism that satisfied requirements beyond those specifically brought by DITA. In particular, any new mechanism needs to play well with namespaces, which the current DITA mechanism does not (but note that it was designed before namespaces were standardized).