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Re: D-AG0007.1- defining reliable and stable WS [was RE: Status: D-A G0007 - reliable, stable, predictable evolution]

From: Hugo Haas <hugo@w3.org>
Date: Wed, 20 Mar 2002 17:55:44 -0500
To: www-ws-arch@w3.org
Message-ID: <20020320225544.GM3477@jibboom.w3.org>
* Hugo Haas <hugo@w3.org> [2002-03-20 17:29-0500]
> I am cathing up on lots of threads, no I will ask the following: has
> "reliability, stability, and predictable evolution of [..] the
> services themselves" been discussed?

I am answering my own question:

  http://lists.w3.org/Archives/Public/www-ws-arch/2002Mar/0309.html

and following up on Suresh's email:

* Damodaran, Suresh <Suresh_Damodaran@stercomm.com> [2002-03-18 16:58-0600]
> I am considering the goal 
> "reliable, stable, and predictably evolvable web services" as D-AG0007.1
> till we get a formal number for it. I volunteer to be the champion of this
> goal
> (unless somebody else (do you want to be?) wants it, that is:-)
[..]
> Stable - A WS is stable as long as any change in WS implementation conforms
> to the independent specification (say WSDL) of the WS for all potential
> users. Note that the specification of WSDL could change, and as long as all
> users/service requesters are
> "aware"/notified of it.

This is where the "predictably evolvable" Web services meets
stability, I think...

[..]
> -----Original Message-----
> From: Hao He [mailto:Hao.He@thomson.com.au]
> Sent: Thursday, March 14, 2002 6:35 PM
> To: Damodaran, Suresh; Hao He; www-ws-arch@w3.org
> Subject: RE: Status: D-AG0007 - reliable, stable, predictable evolution
> 
> 
> hi, Damodaran,
> 
> I would regard the stability of a web service as the stability of the
> identifier (the URI) and the logic concepts associated with it. For example,
> if a company sells car at http://xys.com/buy/car, one expects the URI to be
> stable so one can bookmark this URI and one expect to buy a car not a book. 
> 
> <sd>
> Would you not consider this a "reliability of URI" than a stability issue 
> in light of the discussion above?
> </sd>
> 
> 
> The second part is more tricky.  How about: "the architecture should enable
> a web service to reveal its attributes to its consumers and verified
> independently by its consumers or third parties so a selection mechanism can
> be enforced. "?
> 
> 
> Note the attributes can be more than just those needed in order to discover
> the web service.
> <sd>
> We need a new goal for this (and a champion). Sounds fine to me.
> 
> may be we need 2 - one for "discovery" and another for "criteria based
> selection?"
> </sd>

... and where it relates to the dependency on certain versions as I
was talking about in my email[1].

To me, the stability aspect is that the service will have a interface
and behavior advertised for a particular version, which is I think in
accordance with Suresh's definition.

The predictability of evolution aspect hints that there is a way to
say:
- that one wants to use a particular version.
- that a change in behavior and/or interface, in other words a change
  of version, will be signaled one way or the other (a new URI for the
  new version comes to mind, for example). This is what Suresh was
  refering to with "Note that the specification of WSDL could change,
  and as long as all users/service requesters are "aware"/notified of
  it."

I therefore support such a goal.

Regards,

Hugo

  1. http://lists.w3.org/Archives/Public/www-ws-arch/2002Mar/0349.html
-- 
Hugo Haas - W3C
mailto:hugo@w3.org - http://www.w3.org/People/Hugo/ - tel:+1-617-452-2092
Received on Wednesday, 20 March 2002 17:55:44 GMT

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