SOAP Messaging

["Doug Ransom" <Doug.Ransom@pwrm.com>]

Title: SOAP Messaging

I am poking around some of the more interestingly titled WS specs  to see if they are relevant. I thought I would make some notes on WS-Transfer and WS-Enumeration as well so we know what they are about.  Many of the specs are simply interface definitions.

I hope you will think about them and whether they are relevant.  I don't think its necessary to dispute/approve the relevance of any of these to OBIX at this time (i.e. don't consume your time drafting emails).  These are just for tools for your consideration - I am not proposing any of these.

WS-Transfer is a remarkably simple spec, and the implementation very lightweight.  It is a simple interface with simple semantics.

I found a very concise description at
http://tinyurl.com/6j6tg

The transfer spec is at http://tinyurl.com/4bqle  It might be worth skipping to the appendix simply to review the WSDL.  I think this is potentially interesting if we have store/get/create/delete semantics for xml resources (i.e. a profile of the information I will be repeatedly querying could be configured/stored with WS-Transfer.  The actual OBIX stuff I read might be a different service altogether).

Ws-enumeration is less interesting.  "There are numerous applications for which a simple single-request/single-reply metaphor is insufficient for transferring large data sets over SOAP. Applications that do not fit into this simple paradigm include streaming, traversal, query, and enumeration. ".  If we need database-like cursors for large result sets, this might we worth looking into.

WS-Metadata provides among other things, a simple interface to support requesting a WSDL or XML Schema.  If the structure of an OBIX server were represented in Schema (i.e. every device has its own schema to represent its current structure) this could perhaps return a schema for an entire server. I find the of returning a schema interesting;  Obix does something similar with our own simplified schema (see section 3.2.2.2 of v0.4).

This led me to think there may very well be use cases for requesting WSDL, whether we use WS-Metadata or define our own interface.  Aaron mentioned something this morning about the required dynamic style access to OBIX and its downsides.  Maybe WSDL is an approach that would help?  In Python or dotnet and probably Java and most other platforms, one can compile a WSDL to classes on the fly, create instances, and (the hard part), create and use the data structures required that represent the types encoded in the the soap messages.

Doug Ransom
Energy Analytics Domain Expert
Power Measurement
2195 Keating Cross Road
Saanichton, BC, Canada  V8M 2A5
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E-Mail: mailto:doug.ransom@pwrm.com
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