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Re: Another look at namespaces

• From: "Rick Jelliffe" <ricko@a...>
• To: "Paul Prescod" <paul@p...>
• Date: Mon, 20 Sep 1999 18:11:53 +0800

From: Paul Prescod <paul@p...>

>Rick Jelliffe wrote:
>>
>> Again, Andrew is simply conflating schema and namespace.  The idea
that
>> he and Tim are putting forward is that a language is defined by a
single
>> set of content models; this confuses "language" with "grammar"
>
>What definition of language are you using that does NOT state that
every
>language has one and only one grammar.

The distinction between language and grammar is one of common
English usage (refer to any dictionary) and does not need justification.
To fixate on that subsiduary phrase is to ignore my point.

My meaning would have been clearer if I said:

>> The idea that he and Tim are putting forward is that a (markup)
>> language is  (completely or primarily or fundamentally) defined
>> (as distinct from partially described) by a single set of content
>> models;  this confuses "language" (as common used) with
>> "grammar" (as commonly used).

My evidence for this was that they said that because HTML 4 has
three DTDs, it should have three namespaces.

Only the superficial aspects of a markup language (i.e., its syntax)
can be defined with a content model. Its semantics cannot.

 I could have the same content models as HTML but with completely
different semantics; they are not the same language (as commonly
used), even though they may have the same grammar (as commonly
used).  (This distinction, that the Document Type Definition is not
the same as the markup declarations, is as old as SGML. I have never
heard anyone claim that markup languages are pure syntax with no
semantics (where "semantics" is used not in the sense of in opppsition
to "structure" or "denotation" but in the sense of in opposition to
"syntax".)

(Actually, Tim BL  has clarified that he can go along with the idea that
content models "describe" rather than "define" a language.)


Rick Jelliffe


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