Just some additional comments:
I did find that the main development
problem
getting substitution group (sg) to work
happens
when you miss either an import in a
document
schema or the corresponding namespace
in
the instance. This problem seems to be due
to
the fact that a document schema without
all
the necessary imports can still be valid.
If you
don't have a derived CAC imported into
the
Document schema it is valid but the
instance
won't be able to use the CAC's substitutions
if
1. the derived CAC isn't imported into
the
document
schema
or 2. the instance doesn't include the
derived
CAC's namespace.
Otherwise it is all straightforward in
development provided you have the right
tools.
On the matter of tools though I did find
there
are still some problems with using the
sg's:
even a few up to date mainstream tools still
fail
to validate some valid schemas which use the
sg's.
I general the latest versions of tools are
better
but not all of them are OK yet.
I note the urls sent by Ken a few days ago
show
that there are experts who think sg's have
better
support than redefine.
Regarding redefine though, I don't think
anyone
has yet shown that it can be used in the
UBL
schema architecture for either codelists
or
general minor versionng. Sg's can plainly be
used
though, so I think it is pretty much a no-brainer
-
unless we decide against having any minor
versions at all for UBL. Without any minor
versions
though we might be making it very expensive
for
adopters to keep their implementations up to
date
with updated versions of
UBL. At the same
time
we might be causing fragmentation of
the
implementations if, by the lack of minor
versions
which are polymorphic, we cause it to be
cheaper
to customise than to adopt future versions of UBL.
All the best
Steve
----- Original Message -----
Sent: Monday, July 18, 2005 11:18
AM
Subject: Re: [ubl] Discussion of
substitution groups
Folks,
As we are looking at substitution groups
in
advance of the codelist discussion
(though
leading into it of course) I thought I'll
need
to jump the gun a bit
on prototyping I
adapted
from some work I've been doing
with Marty
(based on his prototypes for codelist
extension).
It uses the latest UBL 2.0 draft
schemas
sent by David over the last few days.
It demonstrates
both
1. Marty's codelist mechanism which now
uses substitution groups * without abstracts *
(personally I'm
all for that following the work
we did with
Arofan, though I still dislike the
abstract element/type method)
2. Arofan's general minor versioning
(and customisation) mechanism which we
worked on in the working team in
April.
Notably, using the latest schemas is
rather more satisfying and assuring
in
that it shows there to be no
development
problem at all in using the
substitution
group / global elements / global
types
(without abstracts) / derivation
mechanism
with our current 2.0 schemas to
produce
a * hypothetical * 2.1 set of extended
minor
version schemas (both BIEs and
codelists
extended).
The attached file can be saved with
extension
.zip then unzipped.
All the best
Steve
----- Original Message -----
Sent: Monday, July 18, 2005 1:41
AM
Subject: RE: [ubl] Discussion of
substitution groups
>Remember that we are discussing substitution
groups (and possible >alternatives to the same) as a code list
extension mechanism in >next week's Atlantic TC call. Given that
Mark Crawford will be >unable to attend, it would be good to have as
much information as >possible (including the outcome of discussions
with Henry >Thompson) posted to this list prior to that meeting,
preferably at >the beginning of the week.
Remember that our
discussions on the use of substitution groups within our UBL NDR needs to
focus on what our requirements are for developing UBL normative schema from
our models for vote by the TC - to include UBL developed code
lists. Customizer requirements are left to the extension
methodology.
Mark ---------------------------------------------------------------------
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