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Re: Myth of loose coupling

From: David Jacobs <djacobs@mitre.org>
Date: Tue, 07 Jan 2003 11:47:00 -1000
Message-ID: <3E1B4AD4.4080401@mitre.org>
To: David Orchard <dorchard@bea.com>
CC: www-ws-arch@w3.org

I agree with just about everything you are saying.  Until AI 
capabilities develop much further, the human interpretation factor will 
provide much looser coupling with HTML than with XML.

However, I think there are things that can be done to start us down the 
road of reducing the very tight coupling that SOAP entails.  This was 
the reason for my other proposal, whereby we standardize the xml schema 
communicating web service navigation and defining web service forms.  In 
this way changes to navigation and forms becomes just data changes 
instead of schema changes.  I agree that resulting data will always 
require tighter coupling, but even here if the client is written 
correctly some flexibility (albeit very limited) in schema changes can 
be endured.


David Orchard wrote:

>I completely understand the flexibility of changing web sites without
>affecting the client.  My argument is that from the client's perspective,
>this is a "data" change, and not an "application" change.  Imagine the
>corollary in Web services.  Web model=use HTML.  Web services=use XML.
>Instead of using the standardized HTML for offering a web site, Amazon
>offers XML.  Now it creates it's own vocabulary of xml.  You write an app
>for that XML.  If Amazon changes the data values - like adds a new book -
>your app doesn't break.  But if Amazon changes the vocabulary of xml, your
>app breaks.  My point is that HTML doesn't evolve very quickly, so the
>clients don't break very often.  But in program to program via XML, this
>situation is completely different.   And because XML allows for much quicker
>changes to vocabularies, programs will break more often.  The browser and
>the Web service client all have the same level of coupling, it's just that
>the vocabularies can change at WAY different speeds.  In fact, I kind of
>argue that XML is a two-edged sword because of this.  XML means we can very
>quickly create new vocabularies.  But the converse of that is that
>clients/servers will break more quickly.
Received on Tuesday, 7 January 2003 16:48:41 UTC

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