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Re: Impact of XML on Data Modeling

From: Anthony B. Coates (Work) <abcoates.work@yahoo.co.uk>
Date: Thu, 31 Jan 2008 00:02:24 -0000
To: xmlschema-dev@w3.org
Message-ID: <op.t5ro2alr9xupjd@laptop01.mileywatts.com>

Designing in XML (e.g. W3C XML Schema) is an attractive option when you  
(and/or your group) are only responsible for the messages that are sent  
between systems.  On the other hand, I know a number of large  
organisations that are busy developing enterprise data models, at a level  
above XML or relational databases or program code, because they want data  
consistency everywhere.  They are concerned with more than just  
consistency in the messaging between systems.

So whether XML schemas are suitable for your modelling needs depends very  
much on what your business scope is, and what your company's longer term  
ambitions are (in terms of having a consistent enterprise data model).   
The "right" choice depends very much on your particular needs and goals.

Cheers, Tony.

On Wed, 30 Jan 2008 23:10:53 -0000, Tsao, Scott <scott.tsao@boeing.com>  

> I was actually trying to focus my attention on the choice of XSD based
> on this observation:
> *	
> 	XML is a better approach for design and implementation at the
> data interchange level, e.g., specifying the interface 'protocol'
> between two systems (or applications).  For example, in the SOA world,
> XML would be very useful as the common modeling 'language' across the
> data and process modeling perspectives.
> And it is definitely for "data-oriented" applications.
> So, having narrowed the scope of my question, do you have any further
> comments?
> Thanks,
> Scott Tsao
> Associate Technical Fellow
> The Boeing Company
> -----Original Message-----
> From: Anthony B. Coates (Work) [mailto:abcoates.work@yahoo.co.uk]
> Sent: Wednesday, January 30, 2008 1:06 AM
> To: xmlschema-dev@w3.org
> Subject: Re: Impact of XML on Data Modeling
> On Wed, 30 Jan 2008 04:33:28 -0000, Tsao, Scott <scott.tsao@boeing.com>
> wrote:
>> If these observations are correct, my next question would be: Is the
>> W3C XML Schema the best choice on the market today for data modeling
>> in the XML world?  (why or why not)
> If your only concern is a single technology, then you can get away with
> only using a physical model.  Which is to say that if XML is your only
> concern, you could do your data modelling in an XML schema language (and
> introducing a logical model might not be very beneficial in practice;
> there is a cost to using layered models, and you generally only get a
> pay back on that cost (a) if you need to implement the same data model
> across multiple technologies, e.g. databases and Java/C# as well as
> XML).
> As for which is best, my personal rule of thumb is that W3C XML Schema
> is the best choice where you are dealing with "data-oriented" XML, i.e.
> XML where there isn't much mixed content, and the sequencing of XML
> child elements within a parent element is often not important to the
> interpretation of the data.  By contract, for "document-oriented" XML,
> i.e. XML where there is a significant amount of mixed content, and the
> sequencing of XML elements is usually important, I would suggest RELAX
> NG (but I say that as someone who works almost exclusively in the
> "data-oriented" world).
> That said, I've worked with customers who have large numbers of complex
> W3C XML Schemas, and if there are lots of "includes" and "imports" that
> introduce dependencies between those Schemas (as there often are), they
> can become difficult to understand and maintain using XML Schema
> editors.
> When things get to that scale, I find it works better to introduce a
> higher-level model of some sort, so that the set of XML Schemas becomes
> more like a repository of re-usable XML types.  Some UML tools now do a
> good job of this, and I also had a lot of real-world success using IONA
> Artix Data Services to create a repository of types from which I
> generated hundreds of Schemas which shared types at the repository
> level, but didn't
> have and Schema "includes", making them easier to deploy and understand.
> Note that this repository isn't a logical model, it's a physical model
> that abstracts away one particular physical issue (which type is defined
> in which file).
> Perhaps that's a long way of saying that for larger scale projects, it
> isn't just about the modelling language that you choose, it's also about
> your methodology for working with large models with complex
> interrelationships between types and other definitions.
> Cheers, Tony.
> --
> Anthony B. Coates
> London, UK
> UK: +44 (20) 8816 7700, US: +1 (239) 344 7700
> Mobile/Cell: +44 (79) 0543 9026
> abcoates.work@yahoo.co.uk

Anthony B. Coates
London, UK
UK: +44 (20) 8816 7700, US: +1 (239) 344 7700
Mobile/Cell: +44 (79) 0543 9026
Received on Thursday, 31 January 2008 01:26:42 UTC

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