XSchema suggestion/wish: Parameter entity (or SGML DTD inclusions/exclusions?) "equivalent"

Rick Jelliffe ricko at allette.com.au
Sun Jan 17 08:14:40 GMT 1999

From: Jarle Stabell <jarle.stabell at dokpro.uio.no>

>Advanced schema languages would be useful for DTD/schema designers even
>without any XML parser knowing that particular schema language, because
>authoring tools could automatically translate the advanced schemas into
>simpler ones.

In effect, the people unhappy with DTDs want "parameter element types"
rather than "parameter entities".

The parameter entity mechanism is based on treating the DTD as text, and
constructing the document that contains the declarations by referencing,
including or ignoring smaller text entities. As TEI's "Chicago Pizza"
model (pick the base elements and then add topping elements) shows,
highly sophisticated DTDs can be successfully made using textual
inclusion. (In fact, just as even C++ programs still sometimes still use
cpp features when the programs are large or complex or multi-targeted, I
doubt the practical wisdom of excluding textual inclusion entirely from
future schema systems.)

Rick Jelliffe

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