[ubl-ndrsc] Fw: Adding children to type derived by restriction

[Dave Carlson <dcarlson@ontogenics.com>]

fyi, this also points out the importance for us not to rely on current
schema validators to assure compliance with the spec.

Dave

----- Original Message -----
From: "Henry S. Thompson" <ht@cogsci.ed.ac.uk>
To: "Mark Feblowitz" <mfeblowitz@frictionless.com>
Cc: "Xmlschema-Dev (E-mail)" <xmlschema-dev@w3.org>
Sent: Tuesday, November 06, 2001 8:29 AM
Subject: Re: Adding children to type derived by restriction


> Mark Feblowitz <mfeblowitz@frictionless.com> writes:
>
> > I sent a similar message to Henry, but I also thought it would be
useful to
> > break it open for wider discussion.
> >
> > I am part of a team that is developing the Open Application
Group's XML
> > Schema version of the OAGIS standard. Before we commit the
grievous sin of
> > including illegal Schema constructs in a proposed standard(!), we
thought it
> > a good idea to ask about particular usage that we're unsure of.
> >
> > There seem to be diverse interpretations regarding allowable
derivations of
> > complex types by restriction. The issue at hand is that of adding
a new
> > child element to a complex type that has been derived by
restriction.
>
> I'm not aware of anyone ever claiming this was allowed by the REC.
> It's not.
>
> > Our understanding, based on reading the Schema Structures spec, is
> > that this is not allowed. But XML Spy, Xerces, and XSV allow this
> > behavior.
>
> XSV's documentation [1] lists:
>
>  "Detailed enforcement of derivation by restriction"
>
> in the Not Implemented Yet section.
>
> The key invariant, which you don't need a validator to check, is
that
> every member of the derived type must be a member of the base type.
> Adding a new child clearly breaks that.
>
> ht
>
> [1] http://www.ltg.ed.ac.uk/~ht/xsv-status.html
> --
>   Henry S. Thompson, HCRC Language Technology Group, University of
Edinburgh
>           W3C Fellow 1999--2001, part-time member of W3C Team
>      2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131
650-4440
>     Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
>      URL: http://www.ltg.ed.ac.uk/~ht/
>
>
>