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RE: Synchronous v/s Asynchronous, a WSA question, and few suggestions

From: Rogers, Tony <Tony.Rogers@ca.com>
Date: Thu, 5 Oct 2006 10:44:13 +1000
Message-ID: <BEE2BD647C052D4FA59B42F5E2D946B3375728@AUSYMS12.ca.com>
To: "Ramkumar Menon" <ramkumar.menon@gmail.com>, <www-ws-desc@w3.org>
In the context of SOAP over HTTP, synchronous means using IN-OUT MEP
with the OUT message travelling on the response of the original HTTP
connection (anonymous URI in replyTo). Asynchonous means that the
response travels on a different HTTP connection (non-anonymous, non-none
URI in replyTo).
Request-Response can be async; just requires a replyTo that does not
specify anon or none.
Tony Rogers
tony.rogers@ca.com <blocked::mailto:tony.rogers@ca.com> 


From: www-ws-desc-request@w3.org [mailto:www-ws-desc-request@w3.org] On
Behalf Of Ramkumar Menon
Sent: Thursday, 5 October 2006 10:09
To: www-ws-desc@w3.org
Subject: Synchronous v/s Asynchronous, a WSA question, and few

I am troubled by a few questions since a few days. Appreciate your
comments in this matter.
a) What defines "synchronous" or "asynchronous" - Are this terms
normatively defined in any related specification ?  Are these terms
"adjectives" for message exchange patterns?  
b) Does "synchronous" interaction require the caller program to "block"
on the response from the service ? [I know it really depends on what
(a)'s answer is]
c) Can't a Request/Response transmission primitive [that wsdl 1.1
defines]  be asynchronous [thru wsdl extensions] ? The specification
does not talk about the relationship between synchronicity and the type
of the transmission primitive. So I assume this does not violate the
conformance requirements. 
d) Is it correct if I state that synchronicity and asynchronicity of an
interaction cannot be defined at the abstract level of a service
definition and depends purely on the transport bindings being used ? [or
if the user employs extensions for the operation in the abstract portion
of the WSDL]  
e) What is the relationship between the transport specified in the WSDL
1.1 Bindings and the ReplyTo/FaultTo requirements that are imposed on
the service ? - confusing question, aint it ? :-) 
Let me explain with an example.
  I define a WSDL 1.1 service with a portType with a
request/response/fault operation. I define WS-A headers for each of the
input, output and fault in the binding section.  I wish to return faults
from this operation to a FaultTo endpoint that is different from the
ReplyTo endpoint. Shouldnt it be possible to send messages to the
FaultTo endpoint on a different transport ? [ i.e. Lets say I wish to
send faults to an Email Address]. Question is as follows - If so, would
this require separate bindings for the operation to be defined within
the WSDL ?". If this answer to this question is "yes", then, since
transports are specified at the operation level, this would require two
bindings, one for http and one over smtp.  And in the second binding,
what does it mean to specify the information for the input and output -
they are unused. :-)  I am gonna get killed for making this assumption ,
but I am really confused on this last point - I maybe wrong here. Or
maybe WSDL 1.1 is tough to gel in with WSA requirements without relying
on some extension mechanism. 
Few other points:-
a) I noticed that Figure 2-1 [xml infoset] in Section 2.2.1 in WSDL 2.0
primer states that an interface should have 1-* number of operations.
This should be changed to 0-*.[since there could be interfaces with zero
operations, for instance, an interface that just defines faults] 
b) Section 2.9.1 in the Core Language Spec states that "A Binding
component that defines bindings for an Interface component MUST define
bindings for all the operations of that Interface component".  Shouldnt
a similar assertion be made regarding the Faults declared in the
interface as well? i.e.  "A Binding component that defines bindings for
an Interface component MUST define bindings for all the faults of that
Interface component"
c) An interesting thought [on wsdl 2.0] - Why cant faults be global to a
description - I have a scenario where the wsdl defines two interfaces -
one for reserving flight tickets for the travel, and one for making
hotel reservations for the travel.Each of these interfaces are served by
two separate endpoints [lets say, outsourced to two different
Both of them throw a fault namely "CreditCardAuthorizationFault" and a
"InsufficientFundsFault". Why cant this fault be declared globally, and
referenced within each of the interfaces ? [I'm being too impractical,
aint I ? :-) ] - But would definitely appreciate an explanation to this
Received on Thursday, 5 October 2006 00:44:22 UTC

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