Open Grid Forum: Data Format Description Language Working Group

OGF DFDL Working Group Call, March-04-2009


Attendees
Mike Beckerle(Oco)
Alan Powell (IBM)
Steve Hanson (IBM)
Tim Kimber (IBM)

Apologies
Dave Glick (drac)


1. XML Schema 1.1

It was agreed that the lack of support for Schema 1.1 in tools, libraries etc would be an inhibitor to DFDL implementations so it was agreed to remain on XML schema 1.0 .

SH highlighted the main isuues with staying on XSD 1.0

1) xs:all improvements - relaxing min/max occurs, allowing wildcards,

I don't see an alternative to our current proposal of dfdl:sequenceKind.

2) weakened wildcard

Either live with this restriction, or say that the DFDL parser will implement the 1.1 rule where an optional element takes precedent over a wildcard and say that if you use this feature of DFDL, you should avoid XML schema tools that implement this UPA check. (It is my understanding that many tools that validate XML Schema for correctness do not include the UPA checks).

These issues need to be resolved.

It was noted thet Schema 1.1 assert only allow reference to children of the item with the assert and that it would be desirable if DFDL was compatible. As there are dfdl use cases were reference to earlier fields is required AP to investigate if assigning earlier fields to variables in sufficient.

2. DFDL;ASSERT and DFDL:DISCRIMINATOR

Discussion to clarify the semantics of assert and discriminator.

Decided that dfdl:discriminator should only be used to resolve choices. TK to investigate if there are other use cases where discriminator would be useful.

dfdl:assert is to ensure that a document is well formed which, while possibly applying similar tests, is separate from validation. Confirmed that assert cannot be turned off.
AP to document semantics.

3. Reducing number of properties

General agreement to reduce properties when they are redundant and don't support a common use case.

LengthKind=NullTerminated,  typeSubstitution, and trimkind.will be removed.

dfdl:format specialization such as dfd;:sequence were also discussed.  It had been pointed out in emails that there are two stable options

- Only dfdl:format with no specializations
- Only specializations and no general dfdl:format.

Supporting both dfdl:format and specialization was felt to be undesirable.
SH point out that the second option was not practical for all constructs as complex type definitions which put properties in scope would require all possible properties.
I was agreed that for dfdl v1 the specializations would be dropped.


4. AOB
To be discussed
- Escape Schemes
- Consuming extraneous data after schema has be used.
-  'Floating' definitions
- Validation ranges and exclusion lists
-  Actions

Next call 11 March 14:00

Meeting closed, 15:00 GMT


Actions raised at this meeting
No
Action
033
04/03: Assert/Discriminator semantics. AP to document. TK to check uses of discriminator besides choice.
034
04/03: AP remove redundant properties

Current Actions:
No
Action
012
AP/SH: Update decimalCalendarScheme
10/9: Not allocated yet
17/9: No update
24/9: Add calendar binary formats to actions
22/10: No progress
16/1: proposal distributed and discussed. Will be redistributed
21/1: add locale,
04/02: changed from locale to specific properties
18/2: Need more investigation of ICU strict/lax behaviour.
020
SH: Resolve packedDecimalSignCodes behaviour depends on NumberCheckPolicy
22/10: No progress
10/12: added how to decide to overpunch and sign position
11/02: proposal largely agreed. SH to make minor changes
18/02: AP to document unsigned type behaviour
25/02: no progress
023
MB: Review Schema 1.1
29/1: AP and SH to talk to Sandy Gao
04/02 Call arranged for Friday
11/02: Call took place. Identified useful changes. Consolidate with previous list.
04/03: decided to stay on Schema 1.0.
024
String XML type
025
Escape schemes
21/1: discussed requirements
04/02: AP/SH to describe behaviour for known length text fields. Need to discuss if comment escapes should be supported.
11/02 new draft distributed:
18/02: SH up document concerns
25/02: SH and AP have refined proposal ready for approval.
04/03: SH and AP have further refined proposal.
026
SH: Envelopes and Payloads
027
Property precedence tables
028
Variable markup
029
 valueCalc (output length calculation)
031
DG: Review dfdl v033
11/02:  Initial comments received
18/02: Will include work items 5 and 12.
032
DG: Investigate compatibility between DFDL infoset and XDM
033
04/03: Assert/Discriminator semantics. AP to document. TK to check uses of discriminator besides choice.
034
04/03: AP remove redundant properties

Closed actions:

034 Work items:
No
Item
001
String XML type (Ian P) - Apr 30, 2008
002
Escape schemes (Ian P) - Apr 30, 2008
003
Variables - ??, 2008 (Mike)
005
Improvements on property descriptions - ??, 2008 (All - split TBD)
006
Envelopes and Payloads (Steve) - Apr 30, 2008
007
(from draft 32) valueCalc (Mike) - ??, 2008   mostly
complete
008
(from draft 32) Property precedence for writing (Steve) - under review
009
(from draft 32) Variable markup (Steve) - Mar 31, 2008   proposal needs writing up
010
(from draft 32) Assertions, discriminators and choice, including discussion of timing option (Suman) - Mar 31, 2008 * in progress *
011
(from draft 32) How speculative parsing works (combining choice and variable-occurence - currently these are separate) ??, 2008 (IBM)  in progress
012
(from draft 32) Reordering the properties discussion: move representation earlier, improve flow of topics ??, 2008 (Alan) * not started *
025
Augmented infoset and unparsing (Alan)   added but needs work
026  Remove duration

complete - specification updated



Alan Powell

MP 211, IBM UK Labs, Hursley,  Winchester, SO21 2JN, England
Notes Id: Alan Powell/UK/IBM     email: alan_powell@uk.ibm.com  
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