RE: XSD to ER Diagram

Thanks, everyone, for the useful advice and valued opinions.
 
Jack Lindsey makes a good point about the sequence in which we are doing
things. One of the reasons why we start with the XSD and then derive an
E-R Diagram is that we wanted our specification "source" to be
represented in an established, independent industry standard format. I'm
not aware of a similarly established format for describing the data
model as richly in a form which can be automatically processed as easily
as XSD. Certainly nothing can match the ease with which a stakeholder's
data file can be validated against our specification.
 
Regards,
David Banbury
 


________________________________

	From: Jack Lindsey [mailto:tuquenukem@hotmail.com] 
	Sent: Saturday, 23 August 2008 11:20 AM
	To: BANBURY David; xmlschema-dev@w3.org
	Subject: RE: XSD to ER Diagram
	
	

	David:

	 

	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 ;-)

	 

	Cheers

	Jack Lindsey

	http://www.dss-snd.gc.ca/publication/en/chap/chap00403.html
<http://www.dss-snd.gc.ca/publication/en/chap/chap00403.html> 

	 





________________________________

	> 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 be
	> 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 very
	> useful throughout development to present the schema as an
	> Entity-Relationship Diagram but deriving an ER Diagram
directly from the
	> 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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________________________________



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