RE: XMI

[Cory Casanave <cory-c@dataaccess.com>]

You will have to clarify what you mean by this, I'm not sure I get it.  The
structure of instances is very well defined by the MOF (Meta-Object
Facility) Meta model and it's representation in XMI, this allows strong
containment of arbitrary objects (attributes - in the UML sense) as well as
weak references.  This Meta-model based structure is much more rigorous than
the base XML structure (the Meta-model for XML is not even part of the
standard).  It would be very easy to query a set of instances defined by an
XMI/MOF model.  Besides attributes and relations it includes the concepts of
hierarchical namespaces (packages).

I also think it interesting that something that is it's second iterations as
an open standard (MOF) and has been used in products and to support such
complex systems as the UML Meta-model is considered "unproven" with the
alternates being technologies that has not even made past a suggestion to
W3C.

It would make much more sense to me to start with MOF/XMI as a baseline and
make whatever adjustments may be needed such that it is suitable for ebXML,
these could then become part of the next MOF revision.

Bias: We have used and implemented MOF based systems and used XMI.  However,
we are not locked into it, we will be satisfied with any solution that
provides a precisely defined, consistent, expressive and technology
independent model.

Regards,
Cory Casanave
Data Access Technologies

> -----Original Message-----
> From:	Martin Bryan [SMTP:mtbryan@sgml.u-net.com]
> Sent:	Friday, May 26, 2000 3:16 AM
> To:	ebxml-core@lists.oasis-open.org; Chris
> Subject:	Re: XMI
> 
> >Getting back to XMI, the XML in the XMI is really quite "flat" because a
> >UML model has no hierarchy.  If you want a hierarchical DTD, then don't
> > choose XMI, but if you want a DTD that can be used to transport
> > faithfully the object instances from the application, then XMI is the
> > tool
> 
> This is the main criticism of XMI. Without structured messages you cannot
> have structured queries. Without structure you end up with having to adopt
> a naming scheme that differentiates the different contexts within which a
> data object occurs. When you name object based on their context they are
> no longer reusable (see BSR for examples). Reusable core components need
> to be context independent. They need to be placed in contexts within
> messages. Therefore the messages need to be hierarchical. Therefore XMI is
> not suitable for ebXML.
> 
> Martin Bryan