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Fwd: Top cloud in triangle/rectangle diagram

From: Francis McCabe <fgm@fla.fujitsu.com>
Date: Fri, 4 Oct 2002 10:57:15 -0700
To: www-ws-arch@w3.org
Message-Id: <B76A4B0A-D7C2-11D6-85E1-000393A3327C@fla.fujitsu.com>

Begin forwarded message:

> From: Francis McCabe <fgm@fla.fujitsu.com>
> Date: Fri Oct 4, 2002  10:56:44  AM US/Pacific
> To: "David Booth" <dbooth@w3.org>
> Subject: Re: Top cloud in triangle/rectangle diagram
> An analysis of this kind would be a useful part of the architecture 
> spec itself; if for no other reason than to hammer home to the 
> reader(s) that there is more than one way of skinning the cat.
> Also of the essence is that however the originating agent discovers 
> the service, the document describing the service is what is critical 
> to the originating agent.
> Frank
> On Friday, October 4, 2002, at 10:39  AM, David Booth wrote:
>> At 09:40 PM 10/2/2002 -0400, Christopher B Ferris wrote:
>>> David,
>>> I don't think anyone disagrees with these points. But a role does 
>>> NOT imply a central place . . . .
>> I understand that you think of the term "a role" as being 
>> all-inclusive, but I don't think it is.  Even asserting that there is 
>> "a role" is making some assumptions.  I'll try to explain more 
>> clearly with some diagrams.
>> Slide1 (attached) views the top of the triangle as "a role".  It 
>> clearly allows any publishing/discovery agency (or "registry" or 
>> whatever you want to call it), but it CLEARLY implies that the 
>> "Publish" and "Find" actions are using the SAME publish/discovery 
>> agency.  (For this reason, I do not advocate this diagram, and I 
>> would hope that no one else would either, except as an example of ONE 
>> style of implementation.)
>> Slide2 (attached) also views the top of the triangle as "a role".  It 
>> SOMEWHAT implies that the "Publish" and "Find" actions are using the 
>> same publish/discovery agency.  However, the cloud makes the 
>> implication less conclusive.  This ambiguity is important because it 
>> suggests that we are not constraining what that top part is or does.
>> Slide3 (attached) shows a rectangle instead of a triangle.  It 
>> doesn't have "a role" at the top, it has TWO roles.  It CLEARLY 
>> suggests that the action of "Publishing" may use an entirely 
>> different agency than the action of "Finding".  For example, the 
>> Service Provider may "Publish" it's description to a UDDI registry, 
>> but the Service Requester may "Find" that description in a 
>> "Jack-Sprat's-Favorite-Web-Services" registry.  (Jack Sprat may be 
>> providing a very valuable service by consolidating WS descriptions 
>> from many sources.)
>> Slide4 (attached) has no role at all for the top part.  The Service 
>> Provider, by some means (spam?), has advertised its description 
>> DIRECTLY to the Service Requester.  From an architectural viewpoint, 
>> there is no third party involved.  (Obviously there may be a third 
>> party involved physically, such as a router, or TCP store-and-forward 
>> nodes, but that is true of any network connection and is irrelevant 
>> from an architectural point of view.)
>> Clearly, our architecture should accommodate all of the above 
>> scenarios.  By drawing the architecture as a triangle with "a role" 
>> at the top, we ARE making some assumptions that reflect certain 
>> biases.  We can mitigate those assumptions: (a) by drawing the top 
>> thing as a cloud instead of an atomic node; (b) by carefully 
>> selecting our labels; and (c) by our accompanying descriptive text.  
>> All three of these techniques are important to use.
>>> No one to my knowledge is advocating an exclusive, centralized model 
>>> for discovery. . . .
>> It is true that nobody has advocated a PARTICULAR or EXCLUSIVE 
>> centralized model, but that wasn't the issue.
>> Some have advocated the use of the word "registry" or "registries" to 
>> refer to the top cloud.  And CLEARLY, for many or most people, the 
>> word "registry" suggests a central or common "meeting place", whether 
>> it is implemented in a centralized or distributed (gnutella) fashion, 
>> and whether there is only one or more than one.
>> We CAN talk about the action of "publishing", and the action of 
>> "finding". But unless we know what mechanisms they use, there is 
>> virtually nothing we can say about the top cloud in the diagrams.  We 
>> cannot even assume that the "Publish" and "Find" actions are 
>> interacting with the same entity.
>>> . . . this inane debate . . . .
>> Well, the debate really isn't about arbitrary terms.  It is about the 
>> underlying architectural assumptions that are implied by our terms 
>> and diagrams.  It is clear that some people have made some 
>> assumptions while others have made others, and we DO need to come to 
>> agreement about those assumptions.
>> -- 
>> David Booth
>> W3C Fellow / Hewlett-Packard
>> Telephone: +1.617.253.1273
>> <Slide1.PNG><Slide2.PNG><Slide3.PNG><Slide4.PNG>
Received on Friday, 4 October 2002 13:57:18 UTC

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