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RE: [xml-dev] U.S. Federal Goverment's Data Reference Model (DRM) XML Sc
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Mike,
Good thoughts - we have not specified a method for
deriving messages from business objects. That is,
the translation of business objects to message
definitions is not "natively" specified/supported by the DRM (as is, for
example, the specification of data assets and their properties) - however, it is
facilitated by the DRM. This type of capability may be supported by a product
such as a registry product, enterprise service bus (ESB) or integration
broker (I've noted more discussion in this thread
on this aspect).
We may,
however, include one or more use cases as part of the DRM that help
federal agencies and other users of the DRM understand how this capability can
be leveraged. One use case that has already
created and presented to the DRM Working Group involves the use of the DRM to
facilitate the "database forward engineering" process (construction of
relational databases from data models, such as logical data models) - this can
certainly be extended to address how the DRM can facilitate the construction of
messages from data models. However, this is sometimes challenging, as most transactions take the form
of verbs while most data elements take the form of
nouns.
So, currently the DRM supports
identifying the exchanges and referencing the data elements that are part of the
exchange (part of the payload). Our goal for the DRM in this is that an
organization receives the ability to determine if a pre-existing exchange is of
value to them.
Regarding the problem
you cite below on overly
mandatory requirements: One elegant
approach to this is the approach that has been taken by the Global Justice XML Data
Model (GJXDM) schemas. In this approach, a base ("conformance") schema
exists with high optionality, and "constraint" schemas are
constructed by users (i.e. those that
need to produce schemas from the conformance schema) to further
constrain/restrict the constructs in the conformance schema, within certain
prescribed boundaries (i.e. constraint schema must represent a valid subset of
the conformance schema).
Hope that
helps--
Joe
Joseph Chiusano
Booz Allen Hamilton
I'm interested in how you tackle the problem of
translating from business object definitions into message definitions. I'm
working with an organization that has designed schemas to represent its (many
hundreds of) business objects, and is now struggling with the question of how
to design messages for application data interchange that are based on these
object definitions. The problem is that messages exchange information about a
business object, and different messages exchange different subsets of the
information. Making all the information mandatory and thereby forcing the
sending application to populate the message with data that the recipient
doesn't want to know seems unproductive; equally, making all the data optional
seems to defeat the purpose of validation. So it seems that one needs a
message definition (=type) for each message that is somehow related to the
schema for the business object, but isn't related to it by one of the
recognized mechanisms of restriction and extension. It needs some kind of
concept of being "derived by projection".
Any thoughts or advice?
Michael Kay
The XML Cover
pages just announced[1] the availability of a draft XML schema[2] for the
U.S. Federal Goverment's Data Reference Model (DRM) initiative. I am posting
this here to invite comments from the broad XML community as to our
approaches for this initiative. A specification for the DRM XML Schema is at
[4] (includes all elements/attributes, their definition, and hyperlinks for
efficient navigation).
I presented[3]
on this schema at last week's First Quarterly DRM Public Forum along with
Mike Daconta (U.S. Department of Homeland Security Metadata Program
Manager), who is leading this vast interagency effort. We discussed the
design factors that we took into account regarding the schema, use of
existing open standards, and other aspects.
If you have
comments or questions, please feel free to (a) submit them per the
instructions in [1], (b) express them directly to me, or (c) express them
here on the XML-DEV listserv.
Thanks,
Joe
(Announcement)
(DRM XML
Schema)
(Presentation on
DRM XML Schema)
(DRM XML Schema
Specification]
Joseph Chiusano
Booz Allen Hamilton
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