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Re: Syntax and semantics

From: Tim Berners-Lee <timbl@w3.org>
Date: Tue, 16 May 2000 20:43:18 -0400
Message-ID: <000101bfbfd4$b184ddf0$dde7adc1@ridge.w3.org>
To: "Paul Prescod" <paul@prescod.net>, <xml-uri@w3.org>, "Jonathan Robie" <Jonathan.Robie@SoftwareAG-USA.com>
Jonathan wrote:
>To me, namespaces are used to disambiguate names, and are used in the
>process of tokenizing. XML DTDs or schemas determine which sentences are
>legal and describe the structure of those sentences. Semantics are not
>contained in XML per se, but in systems that use XML, including RDF, but
>also including many of the everyday programs that munch XML.


In a distributed system, the semantics must be carried by the message.
True, in most cases today semantics are best defined by what program
slurps it up to the right effect. Hence "a quicken input file" defines the
semantics of a bank statement file.  However, on the internet, the
semantics of messages are defined in the specifications of the languages.
They are not arbitrary.  The message conveys a meaning between two
agents operating on behalf of two social entities. The semantics
of HTML tags are not defined in a mathematical way but the semantics
of a bank transfer are. In the future, we will be able to define the
semantics
of a new language by relating it to things like quicken input files,
and also by specifying mathematical properties of the protocols - such
as the relationship between a check and a bank statement.  In the meantime,
we still use English in specifications.  But the crucial thing is to
recognize that
the namespace identifier identifies the language of the message and so
indirectly its meaning. The namespace identifier has to be the hook onto
which
I can hang semantic information.  I don't see any other philosophical basis
for
XML messages having any meaning.  I don't see how any alternative world
would work,
how you would prove that anyone owes you money or that the weather
in Amsterdam is rainy.

Tim
Received on Wednesday, 17 May 2000 03:49:20 UTC

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