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>I work for fairly large company in the Knowledge Management department.
>Basically, we manage all of the engineering documents (with very few
>exceptions). We started out using DTDs, but I am planning to implement XML
>Schema in the next year or so.
This is, again, a non-experience report, no disrepect intended!
>Here is the logic behind this decision:
>1) Support for namespaces
>Our documents have lots of equations, but the original creator of the DTD
>decided not to use MathML because there was no tool support (we are using
>XMetal 3.1, but have upgraded to 4.5/4.6 and have purchased Design Science
>Mathflow). We are now finding that MathML is essential. I know you can
>use the MathML DTD and included in our existing one, but I find it easier
>just to import it in a schema. And our DTD contains two elements with that
>have the same name as elements in the MathML DTD. Some tools complain
>about this (I can't recall if XMetal does, but I know XMLSpy points it
But using XML Schemas will not fix this, unless the math schema also
the duplicates. And if you are moving to use namespaces, the DTDs can be
revvved up to support namespaces as well (though ugly).
>2) Restrict what text content appears inside elements
>All of our documents have dates in them, usually issue date, revision date,
>and approval date. These elements all contain year, month, and day
>elements in their content model. In the DTD system, people can (and do)
>put anything in these elements (for example "Mar" in the month element
>instead of "03", which is the standard here). We do have guidelines and
>the people in my department tend to follow them, but we plan to start
>letting the end user create their own XML documents. I know from
>experience that they don't always 'play by the rules'. Using schema
>validation is a good way to enforce content consistency.
That is a reason against DTDs, not for XML Schemas: RELAX and Schematron
can model the same things, b.t.w.
>I guess I should copy and paste this in word and send it to the W3C!
I am sure they will be interested.