[DFDL-WG] DFDL: Minutes from OGF WG call, 16 Jan 2007 *CORRECTED*

[Ian W Parkinson]

All,

With thanks to Steve for the correction to 1(v). It is Steve, not Simon, 
who will be looking at whitespacing.

Ian



Open Grid Forum: Data Format Description Language Working Group

Weekly Working Group Conference Call
17:00 GMT, 16 Jan 2008


Attendees
Geoff Judd (IBM)
Simon Parker (PolarLake)
Ian Parkinson (IBM)
Alan Powell (IBM)
Steve Hanson (IBM)
Suman Kalia (IBM)


1. Review of Minutes from last week

OGF22 - No update from Mike.
Specification Drafts - Steve and Alan have distributed a version of Mike's 
plan for the next few versions. of the specification with work items 
assigned to individuals. Simon asked for clarification regarding his item 
"2-level description (schema components)" - this covers reviewing and 
updating the DFDL schema abstract data model document (distributed by 
Steve, with the agenda for this meeting) for inclusion in the DFDL 
specification, to replace and extend the existing UML diagram.
Expression Language - Alan will update and distribute a new draft of the 
expression language proposal.
Property Precedence - Steve has prepared a proposal as a Freemind mind map 
and would appreciate any review comments, especially with regard to the 
questions distributed along with the proposal. The group briefly discussed 
some of these, and Steve will email Mike asking for his opinion on some of 
these issues.
Regarding dfdl:escapeScheme, and how it applies when lengthKind=end of 
data - the specification plan includes a review of the escapeScheme 
mechanism and this issue can be discussed then.
While discussing the enum used for dfdl:nullKind, Simon observed that this 
issue has not arisen in PolarLake's parser as it does not have a 
well-developed concept of null.
Steve felt we should perhaps remove the Advanced Text Delimiter 
Supplement.
Entity References - Alan and Ian have been looking at this, and will 
prepare and distribute a revised proposal. Steve will write a proposal to 
cover whitespacing.

(Simon Parker left the meeting)

2. Property Precedence

The group discussed Steve's proposal and its relation to the specification 
document. It was suggested that the specification could list the 
properties of each object in precedence order; and further that the UML 
diagrams could show which properties can be used with each object.


Meeting closed, 17:40 GMT

---


IBM review of UML for DFDL Schema Abstract Model

For convenience, here is the set of comments from IBM regarding the UML 
diagrams in the schema abstract model document.

General:
All associations originating from DFDLSchema should have black diamond 
instead of empty diamond because DFDL schema object would be the owner of 
these objects. Cardinality of relationship is not explicitly shown; I 
think the default cardinality as per standard is 1 which won't be correct 
in this case. e.g. DFDLSchema would have more than 1 global elements/ 
types etc..  Likewise there would be black diamond relationship from 
Element Declaration/Simple Type Definition/ComplexType Definition to DFDL 
Annotation Base. (Suman)
In the open source XML Schema model, there is no explicitly defined object 
for element reference and group reference. Same  XSDElementDeclaration or 
XSDGroupDefintion are used to model references. It is determined 
programmatically and I think it would be better to use the open source XML 
schema model as source model and show relationship of DFDL Annotations 
attached to the XSD schema model. (Suman)

UML for DFDL subset of XSDL :
Need cardinality adding (Steve) 
 White v black diamond not correct (Suman)
What does 'ref' mean on the link from Particle to Element Declaration ? 
(Steve) 
Link  from Complex Type Definition to Particle - this can only be to a 
Model Group subclass (Steve)
May want to add the following pointer to make it complete: complex type 
definition -> (base type) -> complex type definition (Sandy)
I know this is probably not needed by DFDL; but may help to include it for 
completeness. We have it for simple types; may confuse people if it's not 
on compelx types. (Sandy) 

UML for DFDL annotations on XSDL:
Wondering whether this is necessary. It's a middle step, possibly only 
useful to implementors (Sandy)
1st bullet - talks about a limitation in the XSDL model - I'd like Sandy 
to take us through this. MRM carries annotations on groups and group 
refs.(Steve)
1st bullet - the practical limitation appears to be that you can't 
override the properties of a global group on a group reference, like you 
can with elements. Is this going to be an issue? (Steve)
4th bullet - prohibiting dfdl:discriminator on xs:choice seems sensible 
(Steve)
Should "variable definition" be derived from "DFDL annotation base"? 
(Sandy)
The current diagram suggests that "variable definition" can both be part 
of a format base or as a standalone annotation (outside of a format). Is 
this true? (Sandy)
Can "hidden" be viewed as a specialized element reference? (Sandy)
This only implies a "base class" pointer from "hidden" to "element 
reference". There really isn't much benifit in doing this. It just *feels* 
better. Don't feel strongly. (Sandy) 

UML for post-scope resolution and inheritance flattening:
Haven't finished reviewing it carefully. (Sandy)
Inheritance is used much more often in this diagram. e.g. "Any Element 
Wildcard" is derived from both "Occurrence Properties" and "DFDL 
properties Base". Is this intentional? Feels counter-intuitive to me. 
Components should *have* properties, rather than *be* properties. (Sandy)
Wondering whether it makes sense to combine diagrams 2 and 3. That is, a 
single diagram that has everything inherited/flattered, but don't attempt 
to remove properties that are not used at runtime. e.g. keep DFDL Schema 
etc. (Sandy) 



Ian Parkinson
WebSphere ESB Development
Mail Point 211, Hursley Park, Hursley, Winchester, SO21 2JN, UK





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