Re: [ubl] Code list schema

[Paul Thorpe <thorpe@oss.com>]

Hi,

I agree with the distinction between two types of codelists: standard
enumerations and industry-provided codelists.  I agree that one good way
of providing the latter is by requiring that each organization responsible
for a specific industry-provided codelist publish an XML document defining
that codelist.  I agree that the UBL standard should specify a (simple)
schema for such "codelist definition XML documents".  I also agree with
Jon's comment that Tony's proposal supports vastly more functionality than
what we need for UBL and is therefore quite a bit more complex than what
we actually need.

However, I disagree that the UBL TC has to specify a mechanism (or provide
a tool) that converts a codelist definition document into a set of
Schematron assertions or into an XSD schema.

It would be reasonable to write an application capable of extracting
codelist information from a codelist definition XML document.  The
application could simply parse a codelist definition XML document and
populate (or update) its internal representation of the codelist.  Such an
update could occur at any time (even multiple times and for multiple
codelists) during the execution of the application.

If a set of Schematron assertions were available, the application could
run them on each incoming UBL message, but in my view, that is a matter of
how people write their applications.  If someone wants to use Schematron
assertions, they can produce those assertions by themselves.  Similarly,
someone might wish to create a local transformation of a standard UBL
schema, using one or more codelist definition documents as input, by
replacing all the occurrences of the unconstrained simple type that stands
for a codelist item by an enumeration obtained from the corresponding
codelist.  They might then use the transformed schema for validating the
incoming UBL messages.  It would be their choice.  I do not think the UBL
standard should be concerned about either the Schematron assertions or the
transformed XSD schema.  The standard should simply assume that
implementations will read all the codelist definition XML documents
relevant to them before processing the UBL messages.

In conclusion, I suggest that there should be a simple standard XSD schema
for codelist definition documents.  This would provide a uniform way for
organizations to publish their codelists and for applications to read
them.  A codelist definition document should contain a URI that identifies
the version of the codelist.  There is probably an issue on how to
communicate or to negotiate such codelist version URIs among the parties
participating in a message exchange.

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