[DFDL-WG] DFDL: Minutes from OGF WG call, 14 Nov 2007
Ian W Parkinson
PARKIW at uk.ibm.com
Thu Nov 15 05:33:46 CST 2007
Open Grid Forum: Data Format Description Language Working Group
Weekly Working Group Conference Call
17:00 GMT, 14 Nov 2007
Geoff Judd (IBM)
Steve Hanson (IBM)
Suman Kalia (IBM)
Simon Parker (PolarLake)
Ian Parkinson (IBM)
Mike Beckerle (IBM)
1. Information Set Proposal
Following last week's review of the Information Set proposal, Simon
updated the proposal and distributed a new draft, version 7. Alan queried
the reference to empty lists under "No Value", asking if this was
necessary as DFDL does not use a concept of lists - this is carried over
from the XML Information Set specification, and is only theoretical. The
proposal will be distributed wider within IBM to solicit final comments.
2. Review of Revised DFDL Data Grammar
Mike has updated the Data Grammar portion of the DFDL specification, to
take into account the InfoSet proposal, and distributed this via the
DFDL-WG mailing list.
The meeting reviewed the revised grammar, touching upon the following
Both the ComplexContent and ComplexElement productions include a "Prefix"
element. Alan asked whether this duplication was necessary. Steve and
Simon noted that this had not changed during the revision and that there
are cases where this is useful. The meeting agreed not to change this.
Alan asked why we need both Element and ComplexContent in the SequenceItem
production. Element effectively introduces a name.
Simon noted that most of the changes were in the productions, and wondered
what influence the InfoSet proposal actually had on the specification.
Steve said that there had been real changes, for example with
SimpleElement and ComplexElement.
Steve observed that Prefix and Postfix Separators no longer appear in the
productions table. The meeting agreed that these were probably no longer
necessary, and that this was a useful simplification, but to check this
3. Object Constraint Language
The UML diagram in the revised InfoSet proposal uses Object Constraint
Language1 (OCL) to specify an invariant on the Element class. Simon asked
the meeting to consider whether this might be a useful approach in other
sections of the DFDL specification, in particular when describing parser
behaviour. Suman was concerned that it might prove useful only for
specifying parser internals which should not be covered in the language
4. Other Business
Suman asked if we need to define a parser API. Steve suggested that this
should not form part of the language specification, but that there may
need to be other specification documents.
Steve and Alan will be compiling a list of remaining work items to move
the specification towards completion.
Work has started within IBM, to attempt to describe a number of industry
standard data formats, including SWIFT and ISO 8583, using DFDL. Simon has
a long standing work item to attempt to describe a number of custom
application formats. These efforts should help validate the utility of
DFDL and suggest specification revisions.
Thanksgiving is next week - will this affect attendence of next weeks
Meeting closed 17:35 GMT
Mike to comment on the omission of initial prefix Separators and final
postfix Separators from the productions table, in the revised DFDL Data
Grammar. Are these intended to be covered by other elements in the
productions, or do they need to be added?
Object Constraint Language; specification at
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