[DFDL-WG] DFDL: Minutes from OGF WG call, 7 Nov 2007

Thu Nov 8 06:45:37 CST 2007

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
Mail Point 211, Hursley Park, Hursley, Winchester, SO21 2JN, UK

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

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