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Most of this goes into my "incomprehensible to a mere computer scientist"
bucket, but the idea of an anti-schema is one I like. I wonder how many of
the restrictions in the capability of XML Schema disappear if we define the
constraints on a document using expressions such as satisfies(S1) and not
satisfies(S2)?
I expect someone will tell me there is a vast body of theory on forming the
union and intersection of regular grammars...?
Shame that in XSLT and XQuery, failing to validate against a schema is
always a fatal error.
Michael Kay
> -----Original Message-----
> From: Bullard, Claude L (Len) [mailto:len.bullard@intergraph.com]
> Sent: 10 February 2005 16:46
> To: XML Developers List
> Subject: [xml-dev] Schemas As Anti-bodies and Dynamical Systems
>
> Two fun thoughts to ponder:
>
> 1. A common view of the schema or DTD is as a means
> to validate the instance for acceptance. However,
> it is perfectly useful as a means to validate an
> instance for rejection. You can have anti-schemas,
> anti-anti-schemas and so forth given some dynamic
> exchange such as messages which are themselves,
> evolving (the schema is a kind of message).
>
> 2. A URI as a namespace identifier takes a single
> value from an infinite space and uses it to
> label an instance from a potentially infinite
> space (vocabularies are dynamic in time as
> expressed by a schema signature). If we think
> of that variation as motion, then the equations
> evolve in time. If the DTD or schema for a
> vocabulary is considered a classifier, then
> as noted by Farmer and Packard, "in typical
> studies in dynamical systems theory the dimension
> and the components of the state vector are fixed.
> In contrast while the list of variables in the
> immune or classifier systems is always finite,
> its composition varies with time. As components
> are created or destroyed the differential
> equations describing the dynamics change
> and both the dimension N and composition of
> the state vector changes... Of course it is
> possible to embed such a system in an infinite
> dimensional space and view the dynamics as fixed
> in time. We find it more useful though to
> construct an algorithm that generates the
> appropriate dynamical equations in the lowest
> possible dimensional state space and study the
> dynamics in this context." (1)
>
> (1) J.D. Farmer et al./The Immune System, Adaptation and
> Machine Learning
>
> len
>
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