[DFDL-WG] DFDL: Minutes from OGF WG call 2007-10-31

[Mike Beckerle]

OGF DFDL WG Call 2007-10-31

Discussed: Separator semantics via rewriting - Alan Powell (prior to call) 
raised objections to MikeB's treatment of separator properties semantics 
in draft of nulls/optionals/defaults memo.

Mike agrees. This stuff is a mess. Needs to be reworked.

Action item: Mike to rework.

Discussed: Boxed data, i.e., sequences with dfdl:length specifications as 
means of specifying box size surrounding dfdl-described content.

Proposed to drop this from DFDL V1.0. 

Action: examine important formats to see if this feature is needed. We 
know there are formats that use it (IMS blocks), but must they be 
supported in single schemas or is a two-layer via two schemas approach 
acceptable?

Resolved: not dropping this. New  simpler examples are needed which make 
this clearer than the example in the email/memo by Mike. 

(Note: this is the whole section on valueCalc properties. This has already 
been identified as an area needing a write up.)

Discussed: does infoset include things like the representation length of 
items? This information is needed to express output for formats where one 
element stores the rep-length of another. Suman pointed out that this 
information doesn't need to be available in the infoset. The relationships 
between elements of many kinds cannot be expressed directly in terms of 
the infoset, so why require this representation-level relationship to be 
so expressed?

Resolved: infoset does not contain represnetation artifacts like 
representation length. Mike mentioned that it does contain number of 
occurrences for arrays. However, later discussion of infoset brings into 
doubt whether the infoset even knows about arrays.

Discussed: infoset 

Metadata link? Suman has advocated for this. It's an optional thing. SCD 
paths are acceptable to most. Simon maintained that this shouldn't be part 
of the infoset but really is an implementation consideration.

UML model: Discussed that it should match XML infoset terminology and also 
the grammar terminology used in the spec. (note: or the grammar 
terminology be made to conform to the infoset - actually this is more 
likely) Simon's model has arrays as distinct from sequence groups. We 
discussed eliminating arrays as a concept and going to a neutral term that 
captures both sequence groups and arrays (things with children). 

Action: Steve H. and Simon P. to work out remaining infoset issues. 
Provide UML diagram. 


Mike Beckerle
STSM, Architect, Scalable Computing
IBM Software Group
Information Platform and Solutions
Westborough, MA 01581
direct: voice and FAX 508-599-7148
assistant: Pam Riordan 
                  priordan at us.ibm.com 
                  508-599-7046

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