[DFDL-WG] DFDL: Minutes from OGF WG call, 05 Mar 2008

[Ian W Parkinson]

Open Grid Forum: Data Format Description Language Working Group

Weekly Working Group Conference Call
17:00 GMT, 05 Mar 2008

Attendees
Mike Beckerle (Oco)
Steve Hanson (IBM)
Ian Parkinson (IBM)

Apologies
Alan Powell (IBM), Simon Parker (PolarLake)


1. Discriminator Expressions
Recent discussions on the DFDL-WG email list need to be written up for 
inclusion in the specification. It would be useful, as discussed, to 
automatically generate discriminators when converting COBOL copybooks, C 
structs etc. to DFDL schemas. As Mike observed, this will be difficult as 
copybooks and header files do not typically contain enough information to 
generate descriminators.

2. UML diagrams
Steve is happier with the proposed UML diagrams now that they have been 
simplified. We had previously decided to include, in the specification, 
just the diagram showing the supported subset of XML schema.

Now the diagrams are simplified, Simon is planning to attempt to combine 
the three current diagrams into a single diagram. Mike suggested a 
difficulty with these diagrams; some concepts (for example, element 
references) are not treated as real components in XML schema but are used, 
by DFDL, as part of the scoping rules.

3. valueCalc examples
Mike has distributed a set of Powerpoint slides giving examples of 
calculated values, and thanks the group for the feedback. He will add an 
additional example showing output length calculation.

4. Remaining specification work
The plan for draft 32 need to be adjusted as we have now missed many of 
the planned dates. Steve's 'unparser property precedence' item is 
complete; and the discussion on assertions and discriminators has made 
good progress, and need final write-up by Suman. Work on speculative 
parsing still needs to be assigned an owner, probably from IBM's WTX team.

With regard to speculative parsing, Steve wondered whether this might 
affect the ability of an implementation to implement optimisations such as 
lazy parsing. Although this remains an implementation detail and not a 
subject to be covered by the DFDL specification, we will need to describe 
aspects of the behaviour of speculative parsing to be able to define 
uncertainty resolution in DFDL.

Mike will include a review of the list of outstanding work items in the 
agenda for next week's DFDL-WG call.

Meeting closed, 17:35 GMT



Ian Parkinson
WebSphere ESB Development
Mail Point 211, Hursley Park, Hursley, Winchester, SO21 2JN, UK





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