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RE: Role of intermediary

From: Henrik Frystyk Nielsen <frystyk@microsoft.com>
Date: Thu, 25 Jan 2001 10:32:00 -0800
Message-ID: <006401c086fd$1af92f80$308f3b9d@redmond.corp.microsoft.com>
To: "Michah Lerner" <michah@att.com>, <xml-dist-app@w3.org>
No doubt that building gateways is complicated as you have to provide a
mapping of the semantics in one protocol to another protocol. Especially
when the gateway is between application layer protocols like HTTP<-->FTP
for example which was done in the old CERN httpd proxy [1].
 
Some of the complexities can be fixed at a higher layer (like within an
XML Protocol message) but that doesn't work for all features and for
those you simply have to either a) define a mapping or b) rule it out.
Anybody making protocol bindings will have to consider this.
 
Henrik
 
[1] http://www.w3.org/Daemon/ <http://www.w3.org/Daemon/> 

-----Original Message-----
From: Michah Lerner [mailto:michah@att.com]
Sent: Tuesday, January 23, 2001 17:14
To: xml-dist-app@w3.org
Subject: Re: Role of intermediary


Mark's response to Marwan (Re: Role of intermediary) confirms the
requirements or specification do not  preclude an intermediary from
"receiving incoming messages using one protocol binding and forwarding
them using another".  R600
<http://www.w3.org/TR/2000/WD-xp-reqs-20001219/#z600> , R604
<http://www.w3.org/TR/2000/WD-xp-reqs-20001219/#z604>  and R608
<http://www.w3.org/TR/2000/WD-xp-reqs-20001219/#z608>  make this more
precise, and R612 <http://www.w3.org/TR/2000/WD-xp-reqs-20001219/#z612>
identifies HTTP as the normative non-exclusive binding.  The
composability requirement of section 4.4
<http://www.w3.org/TR/2000/WD-xp-reqs-20001219/#N1136>  as well as R505
<http://www.w3.org/TR/2000/WD-xp-reqs-20001219/#z505>  reinforce this
because a priori knowledge should not be required by the endpoints. 

However (there is always a however), the Charter ( 4.6 Protocol
<http://www.w3.org/TR/2000/WD-xp-reqs-20001219/#N1423> Bindings) warns
of potential "semantic complications") with some protocol bindings.
Will the abstract
<http://www.w3.org/2000/xp/Group/1/01/15-abstract-model/> model consider
the practical questions of different bindings between initial XP
<http://www.w3.org/TR/2000/WD-xp-reqs-20001219/#g340> sender and
ultimate XP  <http://www.w3.org/TR/2000/WD-xp-reqs-20001219/#g130>
receiver?  Are there specific use cases for example an SMTP(HTTP) sender
with HTTP(SMTP) receiver?  What about the scenarios of R502
<http://www.w3.org/TR/2000/WD-xp-reqs-20001219/#z502> ? 


What prevents extra complexity (and problems) when endpoints bind to
different protocols? 


Thanks! 


Re: Role of intermediary 

From: Mark Needleman - DRA (mneedlem@dra.com) 
Date: Fri, Jan 19 2001 


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Date: Fri, 19 Jan 2001 15:52:16 -0600 (CST) 
From: Mark Needleman - DRA <mneedlem@dra.com> 
To: Marwan Sabbouh <ms@mitre.org> 
cc: xml-dist-app@w3.org 
Message-ID: <Pine.OSF.3.95.1010119154939.30452M-100000@tourist.dra.com> 
Subject: Re: Role of intermediary 


Marwan 


I dont believe there is and i see the ability to do that as a legitimate

and useful function 
  


Mark H Needleman 
Product Development Specialist - Standards 
Data Research Associates, Inc. 
1276 North Warson Road 
P.O. Box 8495 
St Louis, MO 63132-1806 
USA 


Phone: 800 325-0888 (US/Canada) 
       314 432-1100 x318 
Fax: 314 993-8927 


Email: mneedleman@dra.com 
  


On Fri, 19 Jan 2001, Marwan Sabbouh wrote: 


> I have this question to the group: Is there anything in the spec that
might prevent an intermediary for receiving incoming messages using one
protocol binding and forwarding them using another? 
> 
> Thanks. 
> Marwan 
> 


 
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Received on Thursday, 25 January 2001 13:33:13 GMT

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