Another look at namespaces

Rick Jelliffe ricko at
Mon Sep 20 14:52:26 BST 1999

From: James Tauber <jtauber at>

>> This distinction, that the Document Type Definition is not the same
as the
>> markup declarations, is as old as SGML.
>SGML makes the distinction and I think it is a good one but I don't
>XML does. In XML a DTD is the (formal)grammar defined by the markup
>declarations and no more.

Sure, in XML "This grammar  is known as a document type definition, or
But that just means that in XML we have to use some other term instead
"document type", for example "language".  It does not alter my point.

>Whether one views:
>    vocabulary = names + semantics
>    vocabulary = names + syntax + semantics
>possible determines their standing on the number of namespaces XHTML
>should have.

I think
   namespace = names
    vocabularies = names in namespaces + semantics possibly
        (I can have a vocabulary composed of names from different
   syntactic schema = names in namespaces + syntax
        (e.g. XML DTD)
    language = names + syntax  + semantics
        (where the syntax ideally uses some grammar that actually
captures the
        amount of cohesion between elements.)

Actually, there should be a difference distinguished between a model and
a schema. The schema captures/describes everything about a syntax; the
model merely  captures/describes everything convenient.  So the
in UML allow guard conditions, to allow extensibility: constraints which
don't fit into the grammar types allowed by UML statecharts can be
notated still.

Rick Jelliffe

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