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Re: SOAP Binding Framework, HTTP Binding, MEP documents

From: Paul Denning <pauld@mitre.org>
Date: Fri, 12 Oct 2001 17:34:41 -0400
Message-Id: <5.1.0.14.0.20011012100657.06bdc3f0@mailsrv1.mitre.org>
To: xml-dist-app@w3.org
At 02:53 PM 2001-10-11, David Fallside wrote:
>The request-response MEP is intended as a description that can
>be referenced by different bindings; the WG may consider describing other
>MEPs.

It should be noted that there is a relationship to applications in that 
different bindings may be swapped (e.g., replace HTTP with something else) 
as long as the other binding supports the same MEP.  Applications will need 
to specify which MEPs are expected from the underlying protocol 
binding.  Perhaps applications can define "properties" for the MEPs they 
expect, and the SOAP processor can check whether there is a match between 
the applications MEP needs and the MEPs offered by the binding(s).  Or the 
SOAP processor can use the application MEP-needs property to select the 
appropriate underlying binding (assuming a SOAP processor may have multiple 
bindings simultaneously).  This gets a little into routing, which is beyond 
the scope of the WG, but defining an MEP-needs property would put the hooks 
in place for it.

As suggested above, we need to say something about the transparency of the 
binding to applications and the role of registered MEPs.

We also need to talk more about the rationale for defining transport MEP 
rather than application MEPs.  I imagine WSFL or something similar would be 
more appropriate for application MEPs.  However, I'm wondering how usage 
scenario S7 [2] relates to these MEPs.

I'd like to see some more treatment on timeouts between the request and the 
response.  Do we need a property?

What about HTTP 1.1 [1] persistent connections and pipelining (section 8.1)?

"In order to remain persistent, all messages on the connection MUST have a 
self-defined message length (i.e., one not defined by closure of the 
connection), as described in section 4.4."

We should make it explicit in the SOAP HTTP binding that self-defined 
message length MUST be used.  Do we want to say that it is the job of the 
binding to determine this length, or must SOAP tell the binding what value 
to use (via a property)?  Perhaps we also need a property that can be used 
to explicitly close a connection rather than keep it open.  Is there a time 
limit to how long a persistent connection remains open?

"Servers will usually have some time-out value beyond which they will no 
longer maintain an inactive connection. Proxy servers might make this a 
higher value since it is likely that the client will be making more 
connections through the same server. The use of persistent connections 
places no requirements on the length (or existence) of this time-out for 
either the client or the server."

"Clients that use persistent connections SHOULD limit the number of 
simultaneous connections that they maintain to a given server. A 
single-user client SHOULD NOT maintain more than 2 connections with any 
server or proxy."

Since SOAP HTTP clients, in many case, will not be a "single-user" client, 
we should define a SOAP binding property to specify a maximum number of 
simultaneous connections.


[1] http://www.rfc-editor.org/rfc/rfc2616.txt
[2] http://lists.w3.org/Archives/Public/xml-dist-app/2001Oct/0116.html

Paul
Received on Friday, 12 October 2001 17:35:46 GMT

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