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
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