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Subject: Re: [dita] Proposal for generalized attribute addition

The key statement below is "like you can with elements". In fact you cannot add arbitrary elements in DITA, they must be based on existing elements, which is exactly what we're proposing for attributes. So it's not completely arbitrary, just arbitrary enough :-)

The one place we've seen a consistent requirement for new attributes, by the way, is for new profiling attributes (what get called metadata attributes in the spec). I'm betting that's what the author below was referring to.

Michael Priestley

Dana Spradley <dana.spradley@oracle.com>

08/02/2005 04:34 PM

Michael Priestley/Toronto/IBM@IBMCA
Re: [dita] Proposal for generalized attribute addition

Okay, I understand (theoretically) the ambition to make specialization something more than just an easy way to customize.

But what's wrong with providing both?  Why shouldn't DITA be easy to customize, where customization is application specific and willing to be ignored everywhere else?

And I think making DITA easier to customize with respect to attributes is a big deal to the community of potential users - the following from another list I'm on where someone asked people to summarize their take on DITA:

* What is the worst thing about using DITA?
-- You have to break DITA (or add to it) to do anything useful with
attributes. The DITA committee is developing a solution to this right now.
The problem is that you can't add arbitrary attributes like you can with

Michael Priestley wrote:

It would be accomplished using an entity redefinition, same as with domains.

I think the theoretical advantages are substantial. Under the current model, specialization modules are plug and play: we can determine by inspecting the class and domains attributes what modules are needed for a document type, compare constraints/modules across document types, automatically determine lowest common denomenators between different document types, and generally make information exchange possible on an automatic level across document type boundaries.

If we allow attributes to be part of a specific custom DTD, not part of a specialization, then we los the ability to move that information up the framework or identify which attributes have been added. Instead of having a document type that follows consistent rules that can be automatically compared and ultimately automatically assembled, we have a custom DTD that must be built by hand, customized by hand, and migrated by hand. In other words it no longer operates as part of a framework, because something outside the framework has its hooks in it.

If you view specialization as just a way to make customization easier, what you're saying makes sense. But specialization isa lot more than that. The advantages of specialization, as described above, are based on thought experiments rather than experience simply because DITA is in its early days and there are only a few dozen specializations floating around, at different levels of completeness and at different companies. But if you follow the thought experiment forward, and think of what happens when we have hundreds of specializations across industries and authoring communities and want to manage the differences and commonalities in a consistent and scalable way, specialization delivers what customization cannot: a way to automatically inspect, compare, and reconcile those differences without loss of information or loss of processing capability.

Michael Priestley


Dana Spradley <dana.spradley@oracle.com>

08/02/2005 04:08 PM

Re: [dita] Proposal for generalized attribute addition

That works for me too - though given the only theoretical utility of roundtripping, I'd prefer a more easily parsed option as well.

Again, why not an empty parameter entity (dtd) and attribute group (schema) that you could put anything in all all, and which would be discarded on generalization?

Attributes should actually be easier to specialize than elements, not harder: there's no content model to enforce. So why not throw them wide open? Generic processing can simply ignore the additions.


Michael Priestley wrote:

I was thinking roughly the same thing, although perhaps with "meta" as the generic ancestor, parallel with "props".  If we are willing to restrict the normal content of "meta" to be simple tokens (ie simply don't allow parentheses except in the generalized form) then we could use the exact same model for generalizing/roundtripping both attributes. Effectively we'd have one generic ancestor attribute for conditional processing attributes, and one for anything else. They could also share the same XSLT library for unpacking the conditions if processing is desired in the generalized form (any process that can't handle the generalized form would be considered specialization-unaware).

Michael Priestley

"Paul Prescod" <paul.prescod@blastradius.com>

08/02/2005 03:41 PM

[dita] Proposal for generalized attribute addition

I propose the following:

a) We make a new attribute called "otherattrs" (like otherprops but not
just for selection/filtering)
b) We make a new issue for specializing the "otherattrs" attribute
c) We to synchronize the generalization/specialization mechanism for
"otherattrs" and "props"

In thinking about this, it seems not too difficult at a first
approximation. The main two issues are:

1. Escaping paren characters that would otherwise be confused for
end-of-attribute-value markers.

              * This can be solved by having an escaping mechanism like "two
paren characters resolve to one, three resolve to two etc. A paren
character alone represents an end-of-attribute marker"

2. Keeping track of which attribute values have ALREADY been generalized
so that we don't end up escaping the value over and over again (or
unescaping it wrongly).

              * This can be solved with an architectural attribute that lists
the attributes that are already generalized.

So, for example, I could specialize "otherattrs" with an attribute value
that represents the last-changed-date for an element.

<myel last-changed-date="2005-08-02T12:28:57(-07:00)"/>

Generalized, that might look like:

<p otherattrs="last-changed-date(2005-08-02T12:28:57((-07:00)))"

Still to think through:

a) does this handles multiple levels of specialization well?
b) is there a requirement to handle multiple levels of specialization?
c) what does the processing (e.g. XSLT or CSS) look like to handle
d) is there a more elegant solution than "generalizedprops"? Perhaps by
looking at the domains in scope after generalization?

For me, the answers to questions a-c are also not clear yet for
Michael's current proposal.

Paul Prescod

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