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RE: Myth of Loose coupling

From: <michael.mahan@nokia.com>
Date: Mon, 29 Sep 2003 10:54:08 -0400
Message-ID: <5C76D29CD0FA3143896D08BB1743296A0101CFA0@bsebe001.americas.nokia.com>
To: <dorchard@bea.com>, <www-ws-arch@w3.org>

Is there a role for intermediaries in the loose coupling? I am
thinking a property such as:

- specialized processing, so nodes in the system architecture can
independently apply functonal or optimizing value to the application.

MikeM

>-----Original Message-----
>From: ext David Orchard [mailto:dorchard@bea.com]
>Sent: September 26, 2003 09:01 PM
>To: www-ws-arch@w3.org
>Subject: Myth of Loose coupling
>
>
>
>I'm posting a link as I was asked to before on the start of a 
>discussion on
>loose coupling.
>
>http://lists.w3.org/Archives/Public/www-ws-arch/2003Jan/0115.html
>
>I will say that I have come to have a somewhat revised view on loose
>coupling.  I would say that loose coupling is a combination of 
>properties:
>- extensibility, so that additional information can be added without
>breaking receivers
>- evolvable changes in the interface, so compatible changes 
>can be made.
>- rapidity of changes in the interface
>- on the web, the generic interface constraint, means that applications
>(browsers/search engines) are not dependent upon each site's protocol.
>- asynchrony, so that senders and receivers are decoupled in time
>- stateless messaging, so that senders need fewer messages and 
>hence less
>chance of communication errors
>- use of URIs for identifying resources.  This means that 
>identifiers are
>very constrained and easily transferred.
>- No vendor specific or platform specific constraints on any of the
>technologies used.
>
>I think one can then say that loose coupling is a property that is a
>combination of other properties as I've listed above.  And it 
>seems that
>changing each property/constraint increases the coupling.  For 
>example, a
>web service with no extensibility, that evolves rapidly in incompatible
>ways, an application specific interface, synchronous, stateful 
>messages is
>tightly coupled with it's clients.
>
>This would show that the Web is "mostly" loosely coupled because of the
>extensibility/evolvability in http/html, slow changes in html 
>vocabularies,
>stateless messaging, vendor/platform agnostic.  Yet it is 
>tightly coupled in
>being synchronous.
>
>Another way of looking at this is that Web service 
>technologies do not per
>se mean a service is loosely coupled, it is only through the 
>application of
>constraints to be loosely coupled.
>
>Seem reasonable?
>
>I think this notion of a "combination" property is similar to 
>the visibility
>property, which I argue is a combination of simplicity and percieved
>performance properties.
>
>Cheers,
>Dave
>
>
Received on Monday, 29 September 2003 10:55:34 GMT

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