RE: Views on Web services architecture

 

-----Original Message-----
From: Newcomer, Eric [mailto:Eric.Newcomer@iona.com]
Sent: Monday, July 22, 2002 3:24 PM
To: www-ws-arch@w3.org
Subject: Views on Web services architecture 
 

I find this a very illuminating statement of the "traditional" or non-REST
position.  Can we come up with a label for it?  OMA maybe ... or
"distributed object?"  As Eric says, "RPC" is a red herring.   I'm going to
use the label "OMA" here just as a placeholder for the general orientation
toward web services that Eric describes,  but am not really happy with the
label....

Services have a name, and data inputs and outputs.  The data is exchanged
with the service in the form of a message, which might include fields and
structures to be mapped into and out of procedure or method arguments.  The
service-oriented architecture is recursive, or perhaps inclusive -- meaning
that features and functions within the Web services architecture are exposed
as Web services the same as those created by application developers.  

Just trying to see how much agreement on non-critical issues we might
have... Would you accept "services have an identity" rather than a "name"?
Do you (Eric) have any problem with the notion that a web service identifier
SHOULD be a URI?  
 
 
Let me try a translation into language that's a bit more neutral with
respect to REST vs OMA.  Does anyone have a problem with "a service is
invoked by a message that identifies in detail the action to be taken and
information to be transferred to the service?"  The "action" can be one of
the CRUD operations, or it can be something more domain-specific such as
"accept-order".  Again, I'm not asking Mark to agree that a
non-CRUDdy/RESTful operation is a "good thing", just to see if we can come
up with acceptably neutral language for the WSA document to describe what it
is we're doing.  
 
In the same vein, how about "a service invocation may produce a message that
is sent back to the originator containing the result of the requested
operation." 

 
 Two or more messages may be placed into relationship to emulate an RPC, 

We're struggling with language to define "message exchange patterns"
appropriately across WSA, SOAP, and WSDL, but I think we generally agree on
the concept, and RPC is clearly one of the MEPs that web services can
exhibit.  Are we all more or less on the same page here?  Again, I'm not
seeking agreement on which MEP to use or not use, just on the notion that
there is a web services architecture concept of MEP, and different MEPs are
associated with different architectural styles.

 
 Web services are consistent with established service-oriented architectural
principles represented in products such as MQ Series, Orbix, Tuxedo, and TOP
END.   

Could you (Eric) elaborate on this, or give a reference?  Are these
"service-oriented architectural principles" general to WSA broadly defined,
or just to the style I'm calling "OMA", or both?

Programs or applications that receive Web services messages have associated
semantic information that determines how the message is processed, including
how it is mapped to the program or application, and what information, if
any, is to be carried in a reply message. 
 

Is WSDL "associated semantic information?"  If not, where does this semantic
information come from in today's world?