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2/4/2002 2:45:21 PM, "Roger L. Costello" <costello@mitre.org> wrote:
>
>Subject: Approaches to designing XML messages
>
>I have convinced myself that there are two fundamentally different
>approaches to designing Web service XML messages. They are:
>
>1. The data-oriented approach
>
>2. The action-oriented approach
>
>I believe that which approach a person takes will have serious
>implications on the nature of Web services.
>a. Has someone already articulated the two approaches?
As I understand it, you are distinguishing "messaging" (data
exchange) from "remote procedure calls" (the action oriented
approach). In SOAP terms, the envelope defines the fundamental
message unit or "wire format" (including the identity of the service
that the message is directed to), and RPC is one of a number of
"message exchange patterns" that can be layered on top of SOAP. SOAP
1.1 allowed this, and SOAP 1.2 makes this much more explicit in the
spec.
> b. What are the pros/cons of the two approaches
In SOAP-ese, this would be posed as "under what circumstances is one
message exchange pattern more appropriate than another". I haven't
seen a lot of explicit discussion of this, although it comes up
tangentially on xml-dist-app from time to time and we did have a
discussion here a month ago that discussed messaging vs RPC; Leigh
summarized it at http://www.xml.com/pub/a/2002/01/16/deviant.html
> c. Intuitively, I think that the data-oriented approach
> is the right approach.
Certainly in some situations, especially where "bulk" data transfers
are happening, humans are involved in the processing, and probably
more generally in loosely coupled application architectures. In
others, especially where you want to leverage programmers' more
widespread familiarity with the synchronous RPC paradigm AND you have
the network/security/processing infrastructure to support it,
"actions" make lots of sense.
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