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My organization is currently 100% W3C schema based and I'm wondering if
some of these other tools/approaches might be a fix for some of the
problems we are running into.
Mainly we are having troubles with extensions/restrictions and the
following requirements:
1) No mater what method is used to define an extension or restriction to an
element, internal content choice group, or code list, the resulting data
stream should not be any different. So a technique that required an
xsi:type value would not fit with this requirement, because we do not want
any of the see what we call "schema artifacts" to be in the data stream. If
every possible method for defining an extension required an xsi:Type value
then it would be allowed. We want the minimum impact on the data stream as
possible.
2) We want to tightly validate the original content as well as the extensions.
2a) We want to be able also validate the content from the core
specification and ignore any extensions.
3) Where possible extensions can be based upon the core elements in our
standard. So if someone is creating a new aggregate element and needs an
EffectiveDate element and our standard has one, we encourage them to reuse
our element rather than creating a new.
4) The extension methods should be supported at least by the core tools on
Java and MS platforms. So we test with Xerces-J and MS-XML parsers.
5) We would like to have one standard method of handling extensions and
restrictions; not one solution for restriction, another for extension and
maybe another for handling code values.
We have not found a way to do all of the above, we can answer different
parts but not all the requirements. We essentially have two approaches
currently and would like to find the ultimate solution that answered all of
the above. I'm wondering if RelaxNG or Schematron might help some of this
without creating too much of a burden maintaining these other environments.
Solution 1
We are using redefine for both extension and restriction. We are defining
our code lists in two steps to allow for extension and all our elements are
globally defined. Our codes are fist defined with a unique name with no
enumerated values. We then use redefine to define the content of these
lists in a separate redefining schema. We figure this at least allows some
one to easily manage this file by adding or subtracting values from the
list. Not a perfect solution but it seems to be the only workaround to
allow this.
Solution 2
This other group is using a standard element called <Extensions> that has
as content the xsd:any element. This allows for the validation of the core
standard. We have also been able to use redefine on these elements to allow
us to specify the actual content model (without the xsd:any) so we get
tight validation. This works with Xerces but doesn't work with MS-XML. This
also requires the use of redefine to get restriction, the xsd:any is for
extensions. We have not implement this to allow extensions of internal
choice groups where I think we will get into trouble with indeterminate
content models. For instance, I don't believe this will work:
((a | b| c | extension)?, d?, e?, extension?)
Without a required element between the choice group and the final extension
element, this is non-deterministic. Most of our designs are made up of
optional elements, very few things are actually required.
Any ideas?
..dan
---------------------------------------------------------------------------
Danny Vint
Specializing in Panoramic Images of California and the West
http://www.dvint.com
voice: 510-522-4703
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