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

[Ian W Parkinson]

One correction in the revised minutes below: some duplicate text removed 
from para 2.1. With thanks to Simon for spotting the error.

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: 
1.      There remain two types of information item: Element Information 
Items and Document Information Items. There are now two categories of 
Element Information Item: simple, and complex. 
2.      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. 
3.      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. 
4.      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. 
5.      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. 
6.      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. 
7.      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. 

8.      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. 
9.      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






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