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Re: "From the point of view of the service"

From: Jacek Kopecky <jacek@systinet.com>
Date: 28 Jan 2003 18:01:54 +0100
To: "Amelia A. Lewis" <alewis@tibco.com>
Cc: WS Description List <www-ws-desc@w3.org>
Message-Id: <1043773314.2845.41.camel@krava.in.idoox.com>

Amy,

I agree with Youenn that you're expressing one piece of information in
three places (in your example). That's redundancy with all its pros and
cons. It has to be said that with the names being input and output (and
with fault being the same direction as the element above it) this
redundancy is there already anyway. 

So what we're discussing in this thread is how to say the same thing in
a more accessible way. Personally, I prefer the status quo which is much
nicer in the syntax, while I believe you'd need as much explaining prose
in the spec in any case.

Regards,

                   Jacek Kopecky

                   Senior Architect, Systinet Corporation
                   http://www.systinet.com/



On Mon, 2003-01-27 at 16:17, Amelia A. Lewis wrote:
> The use of the phrase (see subject header) caught my attention over the weekend, and out of idle interest and a desire to stir up the trout pond, I investigated.
> 
> On investigation, it seems to me that the only reason that we need to say that a WSDL instance describes interactions "from the point of view of the service" is because of the <input> and <output> elements.  Without this "point of view" context, "input" and "output" are problematic.
> 
> Suppose, instead, that operation looked something like this?
> 
> <operation mep="http://www.w3.org/2003/13/wsa/meps/request-response"
>            xmlns:rr="http://www.w3.org/2003/13/wsa/meps/request-response">
>   <message name="rr:request" direction="toService" [other attrs] />
>   <message name="rr:response" direction="fromService" [other attrs] />
>   <fault name="rr:xyzzy" direction="fromService" [other attrs] />
> </operation>
> 
> MEPs are already defined in terms of the service (that is, because they use "input" and "output" they are also required to state that the MEP is from the point of view of a service).  This linguistic adjustment, using "toService" and "fromService", makes that explicit.  An additional benefit of placing direction into an attribute (no matter what the content of the attribute; one could imagine continuing to use the ambiguous "input|output" pair) is that fault directionality can now be described as well.
> 
> This may annoy some folks who like the mirror model, but I submit that there are a fair number of MEPs in which the capabilities of the service and the capabilities of the service partner are clearly distinguished, so that it is not inadmissable to designate them server and client.  The requirement that every MEP has a mirror presumes a service-to-service (or peer-to-peer) model, in my opinion, and unnecessarily restricts the universe of services that may be described.
> 
> However, please take this as observation, rather than a proposal.  Should someone find this interesting enough to make a proposal of it, I'll back it, but I don't feel strongly enough to want to argue about (err, I mean "discuss") it.
> 
> Amy!
Received on Tuesday, 28 January 2003 12:02:03 GMT

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