Hi all,
Steve and Mike have asked me to record
minutes at the regular DFDL-WG conference calls. Here are the minutes from
yesterday's meeting - I'd obviously welcome any suggestions you may have
on the format or style of these minutes.
Thanks,
Ian
Open Grid Forum: Data Format Description
Language Working Group
Weekly Working Group Conference Call
17:00 GMT, 7 Nov 2007
Attendees
Mike Beckerle (IBM)
Geoff Judd (IBM)
Steve Hanson (IBM)
Suman Kalia (IBM)
Simon Parker (PolarLake)
Ian Parkinson (IBM)
1. Introduction
The previous meeting left two areas
for consideration: the Information Set (InfoSet) proposal, and the work
regarding defaulting and nulls. This meeting would cover a review of a
revised InfoSet proposal. The defaults/nulls issue has not been progressed.
2. Review of Revised Information
Set Proposal
Steve and Simon have collaborated on
a revision, v6, of the InfoSet proposal. This has been circulated via the
DFDL-WG mailing list.
The meeting reviewed the v6 proposal,
highlighting the following points:
- There remain two types of information
item: Element Information Items and Document Information Items. Element
Information Items. There are now two categories of Element Information
Item: simple, and complex.
- The description of Document
Information Items incorrectly lists a "root" member. This should
be replaced by a "children" member. Geoff pointed out that the
associated UML diagram suggests that a Document Information Item may contain
multiple children; this will be restricted in the text.
- The "dfdl version"
member is now used to describe the version of DFDL to which the InfoSet
conforms; it does not describe the version of the parser generating the
InfoSet. In particular, for an InfoSet to inlcude a dfdl version identifier,
there is now no requirement for that InfoSet to have been generated by
a DFDL parser.
- Mike queried the meaning of
"absolute Schema Component Descriptor"; it should identify a
schema as a whole. This is a term defined by the SCD specification, and
an appropriate citation should be added to the proposal.
- The meeting discussed, at length,
the "data value" member of Element Information Item, which the
proposal lists as being of type String. Mike pointed out that this is insufficient
to distinguish between some binary floating-point values, and suggested
that it should be of a type defined by the "data type" member.
Suman suggested this would also make for a more natural API. Simon remarked
on the precedent set by XML Schema where all values are represented as
strings. Mike closed the discussion advocating dropping the word "String"
from the definition of the "data value" member.
- Suman queried the purpose of
the document information item. This is an in-memory artifact only, which
acts as a container of the InfoSet's data, and has no representation in
a serialization of the InfoSet. This should be clarified in the proposal.
- The proposal now contains a
UML diagram illustrating the object model. The relationship between Parent
and Element requires some clarifying: it should be modelled as a composite
containment relationship.
- Simon highlighted that the "schema"
member of Element Information Item may be either a relative or an absolute
SCD; while the "schema" member of Document Information Item must
be an absolute SCD.
- The current version makes no
mention of arrays, preferring to treat arrays as repeated children with
the same name. The meeting consdered how to denote arrays in the InfoSet,
but opted instead to add a note regarding arrays to the specification.
Mike will circulate his notes regarding
the agreed changes to the spec. Simon will circulate a new version, v7,
incorporating further comments.
3. Other Business
There was no other business.
Meeting closed
Ian Parkinson
WebSphere ESB Development
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IBM United Kingdom Limited - Registered in England and Wales with number
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Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
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Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
3AU