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Re: literals must be self-evident

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Thu, 18 Oct 2001 05:40:46 +0100
Message-ID: <3BCE5D4E.3F09148E@hplb.hpl.hp.com>
To: w3c-rdfcore-wg@w3.org

DanC:
> That is: it's essential that the interpretation of
> an RDF document is a function of the document alone,
> and doesn't vary according to the contents of other
> documents.
> 


I wish to point out a variety of scenarios which do not break the spirit
of this.

Inclusion of/reference to a specific version of a document.

e.g. 
   We use a namespace such as one of the DAML ones which points to a
particular version of DAML. Element tags such as daml:uniqueProperty
will then have meaning that is constrained by axioms in some other
document, but when daml change their axioms then our document does not
change since it refers to the old axioms.

e.g.
   We use an XML schema datatype as defined in the version of XML schema
dated YYYY-MM-DD, e.g. integer. Later the definition of integer may
change, but because our reference to schema is dated we are OK.


Hence, Dan's summary of the issue is, in my view, to some extent a red
herring.

Documents are not self-contained. The web architecture principle is much
more to do with versioning and ensuring that you know which version of a
module you are importing.

In practice, however, version control on the web is weak.

As an example XML Version 1.0 has had a changing concept of lang tag
between it various editions and normative errata. The result is that it
does matter which version of the XML Version 1.0 definition you look at.
While the use of a dated URL in the xml definition looks good, revving
it is so problematic that it has been easier to just clarify and bug fix
the spec without changing it - even when the bug fixes and
clarifications are non-backwardly compatible.

Of course, this too is the RDF position. We should be talking about RDF
1.1, with a new URL. This would ensure that our 'clarifications' are
clearly distinct from the old M&S. However, we all know that changing
the URL breaks every thing, and so we can't.

In summary, my view is that Dan's web architecture principle that he
pointed to is wishful thinking, and the real world (including the web as
we know it), has compatibility problems that just have to be lived with.

Or perhaps, yes there are issues, but it's not our job to fix them.

Jeremy
Received on Thursday, 18 October 2001 00:36:25 EDT

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