[dfdl-wg] Meeting notes 2006-05-10

[Westhead, Martin (Martin)]

Present


Martin Westhead

Bob McGrath

Steve Hanson

Geoff Judd

 


Agenda


 

Two items were discussed this week:

*	Document "DFDL Arrays"
*	Integrating conversions and properties etc.

 

Most of the meeting was spent on the first item. Included below are
Bob's notes on the discussion. The main conclusion of the discussion is
that the approach seems like a very sensible direction. However it
highlighted that we need to start putting in effort on pinning down a
couple of the outstanding issues, context, conversions, XPath/Dpath.

 

Steve undertook to start working on the integration of properties and
convergence. Martin is going to focus on the outstanding issues with
capturing our separators semantics. It was noted the Mike has been
looking at bringing context and scoping together.

 


Discussion on the document entitled "DFDL Arrays"


 

Presents a proposed approach

 

Comments:

 

1. Efficiency is an issue, particularly if there is no way for the user
to

   know how the data is really laid out, which might lead to
dramatically

   inefficient logical models

 

   a) this issue is not limited to DFDL

   b) it would be nice to have a markup to tell how the data is laid out
WRT

      efficient access.  It was argued that this is hard, and shouldn't
be in

      the core DFDL.  But if such a language exists, then it would work
well

      with the proposed approach.

 

2. We hope that clever techniques a la compiler optimizations will be
able

   to create efficient access methods.  E.g., that drill through the
logical

   layers to eliminate multiple data movements.

 

   a) want the model to make this optimization possible

 

3. A third logical model was suggested, which is thought to be similar
to BFD.

   The model would be the 1D array plus a descriptor to say how to
interpret it.

   Essentially, you may not need or want the additional XML logical
model at

   all.

 

   a) look up BFD and correlate with that approach

   b) add this model to the notes

 

4.  The Array examples highlight the need to solve two general issues:

 

   a) path expressions

   b) transforms, WB and BB

 

5. The 'occurs' is out of date, should read 'occursPath'.

 

 

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