The following is the text of an e-mail message sent to the DITA TC list by Jeff Ogden on Sunday afternoon, 11 October 2009:
Here is another updated summary of the issues related to task vs. general task, constraints, conref, and other related matters.
I’ve placed the issues into two groups. The first group includes questions that still need to be resolved. The second group includes issues that I believe have been resolved or deferred.
If I’ve left anything out or there are other questions that need to be discussed and decided, please add them to the list.
Robert wrote an FAQ about constraints that everyone who is interested in this topic should read:
1. There was a preliminary proposal to allow “weak” constraints to be declared. Michael formalized this as a proposal to allow both “strong” and “weak” constraint validation with “weak” being the default. No one raised technical complaints about the original proposal. There has been support for including the proposal as part of DITA 1.2 expressed by several people. There have been reservations about considering the proposal this late in the DITA 1.2 cycle. If the strong/weak constraints proposal goes forward, my assumption is that we will use the default of “weak” in task.dtd and in ditabase.dtd. The proposal requires changes to the written specification, but no changes to the DTDs or XSDs. It may require changes to some implementations, but perhaps not difficult or extensive changes.
Proposal: Accept Michael’s proposal for DITA 1.2 with “weak” conref validation of constraints as the default and “strong” conref validation of constraints something that may be implemented, but is not required..
2. There is an open question about the need to include a second ditabase doctype shell that would include general task rather than strict task. The TC seemed to be leaning toward not including a second ditabase doctype shell, but I don’t think there is a consensus about that and a final decision remains to be made. If a decision is made to include a second ditabase, we would need to pick a location for the additional doctype shell, filenames, a Public ID, and a URI, and the DTDs, XSDs, and the DITA specification would all need to be updated.
Proposal: Include only a single ditabase document type in DITA 1.2.
3. The names we have for task.dtd, generalTask.dtd, task.mod, task.ent, strictTaskbodyConstraint.mod and the associated XSDs, Public IDs, and URIs seem confusing. Would new names for some of the these items help? task.dtd might become strictTask.dtd, task.mod --> genTask.mod, task.ent --> gentask.ent. For compatibility with DITA 1.1 and 1.0 we’d probably need to use the same sort of trick we used with glossary and glossentry, so the old names would continue to work.
Proposal: To make some name changes so that it is clearer what each file includes or does.
4. Any user specializations based on task.mod from DITA 1.0 or 1.1 will switch from being strict to general task based specialization when people move to DITA 1.2 unless explicit action is taken to add the strict task constraint to the specialization. This is pretty much want happened to use with ditabase.dtd. We need to add something to the DITA 1.2 specification warning people about this possibility. Or, if we rename some items as suggested in the previous item, we might be able to avoid this problem by having a genTask.mod, a strictTask.mod, and a task.mod where task.mod would include the strict task constraint.
Proposal: To make a change along the lines of the later suggestion, so that previously existing specializations based on task.mod include the strict task constraint and so do not implicitly change when used with DITA 1.2.
Issues that I believe have been resolved or which have been deferred to DITA 1.3 or 2.0:
5. The TC has decided that strict task rather than general task should be included in the ditabase doctype shell that is included as part of Technical Content. DTDs, XSDs, and the DITA 1.2 specification will all need to be updated.
6. Questions were raised about the constraints mechanism in general and if it was appropriate to use it to implement the new versions of task that are part of DITA 1.2. At the TC meeting two weeks ago Joann made a proposal to abandon the current approach of using constraints to implement general and strict task in DITA 1.2. As an alternative she suggested two peer task specializations both based on topic. Others suggested that implementing strict task as a specialization of general task without using constraints as another approach. After a good deal of discussion, it was decided that we should stick with the current approach of using constraints to implement strict task based upon general task.
7. It has been stated that within a single organization or within a single authoring group, that in general only one version of an information type SHOULD be used within a group and that we should explain why that is the case and recommend that approach somewhere in the DITA 1.2 specification as well as in a best practices document that might be written by the DITA Adoption TC. There were a number of questions about exactly what should be said and where it should be said, but there was agreement that something should be said in both the DITA specification and in a best practices document.
8. There was a question about the wisdom of including both task.dtd (strict task) and generalTask.dtd in the DITA 1.2. Given the previous item we will include both with appropriate warnings and recommendations in the specification and a best practice.
9. There was a lot of discussion about what is and isn’t or what should and shouldn’t be valid when using conref. There was one question about doing conref validation based on content models in DTDs or XSDs rather than information in the domains attribute value. Several people pointed out why DITA doesn’t use the actual content models in the DTDs or XSDs for conref validation and instead uses values from the domains attribute.
10. Many of the issues we’ve been discussing seem to arise from shortcomings of ditabases and shortcomings of DTDs --that a ditabase can only contain a single use (constrained or unconstrained) of a particular info type. We should look for ways to remove or relax these restrictions in DITA 1.3 or 2.0.
11. Eliot added some questions about topic nesting, conref validation, and the domains attribute to the list of things to consider for DITA 1.3.