Layers, again (was Re: fixing (just) namespaces and validation)

David Megginson david at
Wed Sep 8 19:21:24 BST 1999

David Megginson writes:

 > DTDs do two things very well -- they let you validate the surface
 > structure of an XML 1.0 document, and they provide production rules to
 > help with the creation of XML 1.0 documents.  They could be extended
 > to do lots of other kinds of things, but I hardly see the point (ISO
 > 8859-1 could have been extended to include markup, for example, but it
 > would have been a bad idea).

Note that they do two additional things rather more poorly: they
specify the physical makeup of the document, and they provide default
values for attributes.

All the best,


David Megginson                 david at

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