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RE: What is the advantage of RELAX in comparison to Schemas?
- From: "Bullard, Claude L (Len)" <firstname.lastname@example.org>
- To: Bob Kline <email@example.com>
- Date: Tue, 30 Jan 2001 08:18:37 -0600
Yes and no. If done sensibly, context sensitive
constraints in the schema are useful. The problem comes
when the information gets repurposed along a chain
of users. These rules can vary instance to instance,
site to site. Contracting for a schema that works
in all of those sites is much harder if they have
to share narrower and narrower context rules.
It may be that the most practical approach is
to separate out the context rules either into
the application or into a separately cited
document such as TREX, Schematron, etc.
We know we need both but not both all the
time and in all cases. Again, the monolith
definitions can strangle by attempting too
much scope of control along multiple axes.
Centralization gives the illusion of efficiency
but quite the opposite is the case. It simply
leads to the emergence of cross-system checks;
in organizations, committees that consume
resources without creating product. In systems,
interfaces that consume system resources
making sure every local system is behaving
in accordance with global requirements, often
when those requirements add nothing to local
The schema acts as a control. Scope accordingly.
Look at use case for the schema and make very sure
the constraints are shared. Otherwise, let the
locals add what they need as they need them.
Intergraph Public Safety
Ekam sat.h, Vipraah bahudhaa vadanti.
Daamyata. Datta. Dayadhvam.h
From: Bob Kline [mailto:firstname.lastname@example.org]
The most significant difference (from our point of view, at any rate)
between RELAX and W3C's Schema spec is that the former supports
context-sensitive content models. Schematron also supports this
essential feature, which allows you to specify that a certain type of
content is allowed for a given element only if the element's parent is
<X>..</X>, or only if the element contains a certain attribute with a
specific value. Very disappointing that W3C decided to leave this out.