Combining DTDs

Chris von See cvonsee at
Fri Sep 11 20:28:08 BST 1998

At 05:21 PM 9/11/98 +0000, Peter Murray-Rust wrote:
>I agree with this. I have written two DTDs in XML (CML and VHG) both of
>which have to interoperate with other *unknown* DTDs. As a simple example,
>a paper in chemical physics requires (at least) xHTML, MathML, CML, RDF and
>DC. It is inconceivable that a generic DTD can be created that has valid
>content models for all conceivable applications in this domain. [It *is*
>conceivable that the J.Chem Phys produces a DTD and it's also highly
>probable that if J. Phys Chem also does it would use a different one.] I
>cannot see how, except in very carefully regulated domains (such as legal,
>patent, regulatory) it will be possible to combine generic DTDs to provide
>a useful mixture. For example, if someone wishes to embed a <price> in a
><molecule> this is a perfectly possible and reasonable thing to do. Why
>should I say they can't?

I wonder if a mechanism similar to Java's "import" statement would help
address some of the problems in combining DTDs?  If such a mechanism
existed, you could address a DTD and import only the element definitions
you needed (which, hopefully, would either solve the problem of different
definitions for a given element or make you more aware of name collisions
across multiple DTDs).

For example, you could feed your parser something like:

import DTDname.elementname;
import DTDname.m*;
import DTDname.*;

to tell it that it should only recognize and use certain elements from the
named DTD.


"Don't *say* things.  What you *are* stands over you the while, and
thunders so that I cannot hear what you say to the contrary."

--- Emerson, "Social Aims"

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