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RE: XSD to ER Diagram

From: Tsao, Scott <scott.tsao@boeing.com>
Date: Wed, 3 Sep 2008 20:51:21 -0700
Message-ID: <C7A7D8EA54C20744BFF861613617222C0959778F@XCH-NW-3V1.nw.nos.boeing.com>
To: "Jack Lindsey" <tuquenukem@hotmail.com>, "BANBURY David" <david_banbury@rta.nsw.gov.au>, <xmlschema-dev@w3.org>
"UML and XSD are a much closer match in terms of their respective
feature sets, which is one reason why UML tools are more commonly seen
when modelling for XML implementations..."
I wonder if you could elaborate on this more, as I don't understand
(theoretically) why UML would be a better notation for mapping into XSD
than E-R.
As far as I know, there is a standard for E-R (or RDB) mapping to XML
(i.e., SQL/XML), just as a standard for UML mapping to XML (i.e., XMI).
So, why would UML be a much closer match than E-R.
Please excuse my ignorance... Am I comparing apple with orange?

Scott Tsao 
Information Architect - Associate Technical Fellow
The Boeing Company 


From: Jack Lindsey [mailto:tuquenukem@hotmail.com] 
Sent: Friday, August 22, 2008 6:20 PM
To: BANBURY David; xmlschema-dev@w3.org
Subject: RE: XSD to ER Diagram



I hope you don't mind if I say I find this scenario a little perverse.  


If your community of interest considers an E-R model an effective means
of communication (as pointed out it can only represent a subset of XSD)
why not publish your data requirements in the form of an E-R data model
and then generate the XML schema from it?  Some participants might find
the common E-R model a useful basis for producing a RELAX-NG schema or
an SQL database design or other physical implementations.


In other words, why implement and then model?  Why not model first and
then implement, in as many media as participants desire?


Embarcadero probably has the most to offer in this arena.  It allows you
to specify your own set of standardized XSD data types, for instance.


Umodel is for UML, not E-R, although UML modelling tools can be used to
represent E-R models if you have the discipline to restrict your use of
UML features.  UML and XSD are a much closer match in terms of their
respective feature sets, which is one reason why UML tools are more
commonly seen when modelling for XML implementations.  But once again,
it is usually the UML that is used to automatically generate the XML
schema, not the other way around.


As for ERwin XML, the last time I saw it, it was their own format (not
XMI or anything) for exporting and importing an ERwin E-R model,
complete with graphical positioning information.  For instance, we used
it to export a data model and run it against the names in a data
dictionary so we could generate a French version from the English
version (naturally we had to spread the entity boxes out a bit
afterwards because the French names were longer - perhaps we should have
gone in the reverse direction ;-)



Jack Lindsey




> Date: Fri, 22 Aug 2008 14:36:32 +1000
> From: David_BANBURY@rta.nsw.gov.au
> To: xmlschema-dev@w3.org
> Subject: XSD to ER Diagram
> Please excuse me if this query does not directly concern specific XSD
> issues but I hope it is related closely enough to XSD development to
> worthy of the group's learned opinion.
> We are using XSD to define an XML file format for data interchange. As
> such the schema is not directly related to a specific system or
> database. The schema relies heavily on key-keyref relationships to
> describe the relational structure of the data model. It has proven
> useful throughout development to present the schema as an
> Entity-Relationship Diagram but deriving an ER Diagram directly from
> XSD has been problematic.
> Are there any tools available which will automatically generate an ER
> Diagram from XSD?
> Thanks for any information you can provide.
> Regards,
> David Banbury
> Traffic Systems Branch
> Roads & Traffic Authority of NSW
> Australia
> Tel: +61 2 8396 1417
> Fax: +61 2 8396 1600
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Received on Thursday, 4 September 2008 03:52:14 UTC

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