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Re: Yet another attempt to fix D-AC004

From: Mark Baker <distobj@acm.org>
Date: Tue, 25 Jun 2002 13:59:22 -0400
To: michael.mahan@nokia.com
Cc: www-ws-arch@w3c.org
Message-ID: <20020625135921.N7219@www.markbaker.ca>

Hi Mike,

On Tue, Jun 25, 2002 at 01:20:02PM -0400, michael.mahan@nokia.com wrote:
> Issue: AC004 has been trimmed down to say:
>   "does not preclude any programming model"
> yet the contained CSFs and requirements are not relevant to this concept. 
> They are relevant to the concept of the architecture being comprised of
> loosely-coupled components primarily articulated in D-AC004.3.
> So I propose the new top level CSF:

I like the idea of breaking out those requirements into a separate CSF,
for the reason you give.  But I have some concerns;

> X 'is comprised of loosely-coupled components and their interrelationships' 

What does "loosely coupled" refer to here?  In my experience, the most
common use is wrt coupling between interface and implementation, but it
has other meanings.  We should be clear what we mean.

> with the following subordinate requirements (from synthesizing D-AC004.2, 
> D-AC004.3 and AR004.2):
> AR00X.1 components are [minimally] defined in terms of unambiguous, well-
>         defined interfaces.

An interface is definitely an important part of a component, but I
wouldn't say that it defines the component.

X.2 below says what I think needs to be said, so I'm not sure what X.1

> AR00X.2 component interfaces define their inputs and outputs and also the 
>         form and constraints on those inputs and outputs.

What did you mean by "form" here?

> AR00X.3 component relationships are described in terms of messages and 
>         message transmission protocols.

I'm unclear what you mean by "message transmission protocols".  If you
mean an application protocol, then I'd say that it defines the interface
more than any relationships.

> AR00X.4 messages are transmitted and consumed by the component interfaces 
>         that make up the architecture.

Ok, but seems motherhood-and-apple-pie-ish to me.

> AR00X.5 use XML based techniques for defining messages/protocols for 
>         invoking web resources. (was D-AR004.3)

Well, we've talked about using SMTP and HTTP for Web services, for
example, and those don't use XML.  So I'd like to remove this one.  I'd
suggest toning it down, but as it's a requirement, it wouldn't do much
good to do that, so might as well remove it.

> As for AC004 ("does not preclude any programming model"), I believe we 
> should reuse the XMLP verbiage:
> 'The specification will make reasonable efforts to support (but not define)
> a broad range of programming models suitable for the applications intended
> for XP.'
> and say
> AR004.1 Support (but not define) a broad range of programming models suitable 
> for Web Services applications.

Sounds good.

Mark Baker, CTO, Idokorro Mobile (formerly Planetfred)
Ottawa, Ontario, CANADA.               distobj@acm.org
http://www.markbaker.ca        http://www.idokorro.com
Received on Tuesday, 25 June 2002 13:48:55 UTC

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