Open Grid Forum: Data Format Description Language Working Group

OGF DFDL Working Group Call, May-20-2009

Meeting opened, 14:00 UK

Attendees
Steve Hanson (IBM)
Mike Beckerle (Oco)
Suman Kalia (IBM)
Alan Powell (IBM)

Apologies
Dave Glick (drac)

Agenda:

1. Go through actions.
Updated below:

2. Codepage for text items in infoset.
It is proposed that text values in the infoset should be ISO10646.
Agreed

3. Annotations on Top Level element
Highlighted usability problem that the top level element cannot inherit dfdl properties from scope as no complex type has be used yet. A reference to a defineFormat needs to on both the top element and its complex type. Suggested that could add a defineFormat property that used that defineFormat to set defaults for the schema but that would cause problems with include/import. Solutions seemed worse than the problem so will leave it as it is.

4 .Scoping of elements and Types
MB has pointed out a problem with the current scoping rules and proposed that propoeties on an element should override those on its type.

Discussion on whether an element was an instance of a simpleType or enclosed a simple type. For example if dfd:initiator on both element and simple type do you get one or two initiators.. Also discussed separating dfdl properties between element and type so that none were common. The need to be able to use XSD simple types directly made this impossible. Decided that an element is an instance of a simple type and that properties on the element override those on the simple type. Noted that this is different from complex type.
Action: AP to document change to simple type scoping rules.

5. Scoping rules for assert/discriminator and other annotations
The scoping rules for non-format annoations are not defined. AP to make a proposal

6. Need for the equivalent of WTX Restart
Restart indicates where in the schema to restart parsing when unable to correctly parse content

Could be viewed as an implementation decision. More investigation needed

7. Built-in Specifications
Spec Section 23 Built-in Specifications
TBD: this section gives the names, import URLs for, rep-property definition sets, property definitions, etc. for the built-in named format definitions

The intention is that a small number of built-in specifications are provided for common format styles.

8. AOB
Next call 27 May 14:00 UK Scheduled for 1 hour

Meeting closed, 16:10 UK

Actions raised at this meeting

No
Action

045
20/05 AP: Speculative Parsing

046
20/05 AP: Document changes to simple type scoping

047
20/05 AP: Scoping for non-format annotations

048
20/05: AP investigate Restart

049
20/05 AP Built-in specification description and schemas

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.
08/04: Not discussed
22/04: AP to complete asap once the ICU strict/lax behaviour is understood.
29/04: No progress
06/05: No progress
13/05: Calendar has been added to latest spec version v034 but still a few details to clarify.
20/05: No Progress

026
SH: Envelopes and Payloads
08/04: Not discussed explicity, but recursive use of DFDL is tied up with this
22/04: Two aspects. Firstly compositional - do sufficient mechanisms exist to model an envelope with a payload that varies. Secondly markup syntax - this might be defined in the envelope.
The second of these is very much tied up with the variable markup action 028, so will be considered there. SH to verify the composition aspect.
29/04: SH and AP working on proposal. related to Action 028
06/05: No progress
06/05: No progress
20/05: No Progress

027
SH: Property precedence tables
08/04: Not discussed
22/04: Two things missing from the existing precedence trees. Firstly, does not show alternates (eg, initiator v initiatorkind). Secondly, need a tree per concrete DFDL object (eg, element). SH to update.
29/04: No progress
06/05: SH is updating tables which will be ready for next call
13/05: SH emailed updated version. AP commented.. See minutes for issues and property changes.
20/05: Updated version circulated. Review before next call and be ready for vote.

028
SH: Variable markup
08/04: Discussed briefly at end of call, IBM to see whether there any use cases that require recursive use of DFDL.
15/04: Use case was distributed and will be discussed on next call.
22/04: The use case in question is EDI where the terminating markup for the payload segments is defined in the ISA envelope segment. The markup is modelled as an element of simple type where the allowable markup values are defined as enums on the type. But we need to handle two cases - firstly where the envelope is present, so the value used by the payload is taken from the envelope. Secondly where only the payload is present. Here we need a way of scanning for all the enum values, and adopting the one we actually find, when parsing. And using a default when unparsing. SH to explore use of a DFDL variable, where the variable has a default, but also has a type that is the same as the markup element - that way we get to use the enums without defining everything twice.
29/04: SH and AP working on proposal.
06/05: No progress
13/05: No progress
20/05: No Progress

029
MB: valueCalc (output length calculation)
08/04: Not discussed
22/04: Action allocated to MB, this is to complete the work started at the Hursley WG F2F meeting.
29/04: No progress
06/05: MB will have update for next call
13/05: MB will have update for next call
20/05: Some progress. will be circulated this week

032
DG: Investigate compatibility between DFDL infoset and XDM
08/04: No update
22/04: No update
29/04: No update
06/05: DG indicates will have update next week
13/05: see minutes
20/05: No Progress

033
AP/TK: Assert/Discriminator semantics. AP to document. TK to check uses of discriminator besides choice.
08/04: In progress within IBM
22/04: Waiting for TK to return from leave to complete.
29/04: TK has sent examples shown need for discriminators beyond choice. Agreed. MB to respond to TK
06/05: Discussed suggestion of adding type indicator to discriminator. MB to provide examples.
15/03: Semantic documented in v034. MB to provide examples of need for scope indicator on discriminator
20/05: MB to provide examples of need for scope indicator on discriminator (but lower priority than action 029)

036
SH: Provide use case for floating component in a sequence
08/04: Raised
15/04: Use case sent and discussed. SH to do further investigation
22/04: IBM feedback from WTX team is that alternate suggested ways of modelling the EDI floating NTE segment have significant usability issues. The DFDL principle is that for a problem that can be expressed as two-layered, then two DFDL models are needed. The EDI NTE segment does not fall into this though, as its use is on a per sequence basis. Ongoing.
29/04: Agreed that need to be in V1. SH to make a proposal
06/05: No progress
20/05: SH has almost completed the proposal

037
All: Approach for XML Schema 1.0 UPA checks.
22/04: Several non-XML models, when expressed in their most obvious DFDL Schema form, would fail XML Schema 1.0 Unique Particle Attribution checks that police model ambiguity. And even re-jigging the model sometimes fails to fix this. Note this is equally applicable to XMl Schema 1.1 and 1.0. While the DFDL parser/unparser can happily resolve the ambiguities, the issue is one of definition. If an XSD editor that implements UPA checks is used to create DFDL Schema, then errors will be flagged. DFDL may have to adopt the position that:
a)DFDL parser/unparser will not implement some/all UPA checks (exact checks tbd)
b) XML Schema editors that implement UPA checks will not be suitable for all DFDL models
c) If DFDL annotations are removed, the resulting pure XSD will not always be valid (ie, the equivalent XML is ambiguous and can't be modelled by XML Schema 1.0)
Ongoing in case another solution can be found.
29/04: Will ask DG and S Gao for opinion before closing
06/05: Discussed S Gao email and suggestions. Decided need to review all XML UPA rules and decide which apply to dfdl.
20/05: SH or SKK to investigate

038
MB: Submit response to OMG RFI for non-XML standardization
22/04: First step is for MB to mail the OGF Data Area chair to say that we want to submit
29/04: MB has been in contact with OMG and will sunbit dfdl.
06/05: MB has prepared response to OMG. Will send DFDL sepc v033
20/05: Response has been sent to OMG based on v034

039
SKK: Approach for creating Schema-For-DFDL xsds.
22/04: Resolve issue around multiple declarations needed for DFDL properties, perhaps using MB's meta approach
29/04: Don't like qualified attributes in long form. SKK to check there are no code gen implications, eg EMF.
06/05: SKK will send update by Friday
20/05: SKK and MB have produced Schema for DFDL, XSD dfdl subset and examples.. Close

042
MB: Complete variable specification.
To include how properties such as encoding can be set externally. Must be a known variable name.
06/05: No progress
20/05: AP to make proposal

043
13/05: Types in the infoset. Currently infoset types have defined value space but that implies a parser would have to validate input. Is this correct?
20/05: SH No progress

044
13/05: Bidi
20/05: AP: will check what IBM products support.

045
20/05: AP: Speculative parsing

Closed actions:

039
SKK: Approach for creating Schema-For-DFDL xsds.
22/04: Resolve issue around multiple declarations needed for DFDL properties, perhaps using MB's meta approach
29/04: Don't like qualified attributes in long form. SKK to check there are no code gen implications, eg EMF.
06/05: SKK will send update by Friday
20/05: SKK and MB have produced Schema for DFDL, XSD dfdl subset and examples.. SKK owner of dfdl schema and will update as properties change
Closed

040
SH: LengthKind on complex objects.
29/04: All send comment before next call
06/05: See minutes. Agreed to remove lengthKind from sequence and choice.
20/05: Closed moved to workitem

041
AP: UnorderedInitiated
29/04: All: Review for next call
06/05: See minutes: Agreed to generalize to all sequences
20/05: Closed. Move to work item

Work items:

No
Item target version status

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

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
027 Calendar schemes 034
032 Floating components
033 Changes from action 020 and 027 - renaming properties etc
035 Remove unorderedInitiated, add initiated content (a041)
036 Update dfdl schema with change properties (Suman)
037 Infoset text codepage
038 Improve length section

Alan Powell

MP 211, IBM UK Labs, Hursley, Winchester, SO21 2JN, England
Notes Id: Alan Powell/UK/IBM email: alan_powell@uk.ibm.com
Tel: +44 (0)1962 815073 Fax: +44 (0)1962 816898

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

No	Action
045	20/05 AP: Speculative Parsing
046	20/05 AP: Document changes to simple type scoping
047	20/05 AP: Scoping for non-format annotations
048	20/05: AP investigate Restart
049	20/05 AP Built-in specification description and schemas

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. 08/04: Not discussed 22/04: AP to complete asap once the ICU strict/lax behaviour is understood. 29/04: No progress 06/05: No progress 13/05: Calendar has been added to latest spec version v034 but still a few details to clarify. 20/05: No Progress
026	SH: Envelopes and Payloads 08/04: Not discussed explicity, but recursive use of DFDL is tied up with this 22/04: Two aspects. Firstly compositional - do sufficient mechanisms exist to model an envelope with a payload that varies. Secondly markup syntax - this might be defined in the envelope. The second of these is very much tied up with the variable markup action 028, so will be considered there. SH to verify the composition aspect. 29/04: SH and AP working on proposal. related to Action 028 06/05: No progress 06/05: No progress 20/05: No Progress
027	SH: Property precedence tables 08/04: Not discussed 22/04: Two things missing from the existing precedence trees. Firstly, does not show alternates (eg, initiator v initiatorkind). Secondly, need a tree per concrete DFDL object (eg, element). SH to update. 29/04: No progress 06/05: SH is updating tables which will be ready for next call 13/05: SH emailed updated version. AP commented.. See minutes for issues and property changes. 20/05: Updated version circulated. Review before next call and be ready for vote.
028	SH: Variable markup 08/04: Discussed briefly at end of call, IBM to see whether there any use cases that require recursive use of DFDL. 15/04: Use case was distributed and will be discussed on next call. 22/04: The use case in question is EDI where the terminating markup for the payload segments is defined in the ISA envelope segment. The markup is modelled as an element of simple type where the allowable markup values are defined as enums on the type. But we need to handle two cases - firstly where the envelope is present, so the value used by the payload is taken from the envelope. Secondly where only the payload is present. Here we need a way of scanning for all the enum values, and adopting the one we actually find, when parsing. And using a default when unparsing. SH to explore use of a DFDL variable, where the variable has a default, but also has a type that is the same as the markup element - that way we get to use the enums without defining everything twice. 29/04: SH and AP working on proposal. 06/05: No progress 13/05: No progress 20/05: No Progress
029	MB: valueCalc (output length calculation) 08/04: Not discussed 22/04: Action allocated to MB, this is to complete the work started at the Hursley WG F2F meeting. 29/04: No progress 06/05: MB will have update for next call 13/05: MB will have update for next call 20/05: Some progress. will be circulated this week
032	DG: Investigate compatibility between DFDL infoset and XDM 08/04: No update 22/04: No update 29/04: No update 06/05: DG indicates will have update next week 13/05: see minutes 20/05: No Progress
033	AP/TK: Assert/Discriminator semantics. AP to document. TK to check uses of discriminator besides choice. 08/04: In progress within IBM 22/04: Waiting for TK to return from leave to complete. 29/04: TK has sent examples shown need for discriminators beyond choice. Agreed. MB to respond to TK 06/05: Discussed suggestion of adding type indicator to discriminator. MB to provide examples. 15/03: Semantic documented in v034. MB to provide examples of need for scope indicator on discriminator 20/05: MB to provide examples of need for scope indicator on discriminator (but lower priority than action 029)
036	SH: Provide use case for floating component in a sequence 08/04: Raised 15/04: Use case sent and discussed. SH to do further investigation 22/04: IBM feedback from WTX team is that alternate suggested ways of modelling the EDI floating NTE segment have significant usability issues. The DFDL principle is that for a problem that can be expressed as two-layered, then two DFDL models are needed. The EDI NTE segment does not fall into this though, as its use is on a per sequence basis. Ongoing. 29/04: Agreed that need to be in V1. SH to make a proposal 06/05: No progress 20/05: SH has almost completed the proposal
037	All: Approach for XML Schema 1.0 UPA checks. 22/04: Several non-XML models, when expressed in their most obvious DFDL Schema form, would fail XML Schema 1.0 Unique Particle Attribution checks that police model ambiguity. And even re-jigging the model sometimes fails to fix this. Note this is equally applicable to XMl Schema 1.1 and 1.0. While the DFDL parser/unparser can happily resolve the ambiguities, the issue is one of definition. If an XSD editor that implements UPA checks is used to create DFDL Schema, then errors will be flagged. DFDL may have to adopt the position that: a)DFDL parser/unparser will not implement some/all UPA checks (exact checks tbd) b) XML Schema editors that implement UPA checks will not be suitable for all DFDL models c) If DFDL annotations are removed, the resulting pure XSD will not always be valid (ie, the equivalent XML is ambiguous and can't be modelled by XML Schema 1.0) Ongoing in case another solution can be found. 29/04: Will ask DG and S Gao for opinion before closing 06/05: Discussed S Gao email and suggestions. Decided need to review all XML UPA rules and decide which apply to dfdl. 20/05: SH or SKK to investigate
038	MB: Submit response to OMG RFI for non-XML standardization 22/04: First step is for MB to mail the OGF Data Area chair to say that we want to submit 29/04: MB has been in contact with OMG and will sunbit dfdl. 06/05: MB has prepared response to OMG. Will send DFDL sepc v033 20/05: Response has been sent to OMG based on v034
039	SKK: Approach for creating Schema-For-DFDL xsds. 22/04: Resolve issue around multiple declarations needed for DFDL properties, perhaps using MB's meta approach 29/04: Don't like qualified attributes in long form. SKK to check there are no code gen implications, eg EMF. 06/05: SKK will send update by Friday 20/05: SKK and MB have produced Schema for DFDL, XSD dfdl subset and examples.. Close
042	MB: Complete variable specification. To include how properties such as encoding can be set externally. Must be a known variable name. 06/05: No progress 20/05: AP to make proposal
043	13/05: Types in the infoset. Currently infoset types have defined value space but that implies a parser would have to validate input. Is this correct? 20/05: SH No progress
044	13/05: Bidi 20/05: AP: will check what IBM products support.
045	20/05: AP: Speculative parsing

039	SKK: Approach for creating Schema-For-DFDL xsds. 22/04: Resolve issue around multiple declarations needed for DFDL properties, perhaps using MB's meta approach 29/04: Don't like qualified attributes in long form. SKK to check there are no code gen implications, eg EMF. 06/05: SKK will send update by Friday 20/05: SKK and MB have produced Schema for DFDL, XSD dfdl subset and examples.. SKK owner of dfdl schema and will update as properties change Closed
040	SH: LengthKind on complex objects. 29/04: All send comment before next call 06/05: See minutes. Agreed to remove lengthKind from sequence and choice. 20/05: Closed moved to workitem
041	AP: UnorderedInitiated 29/04: All: Review for next call 06/05: See minutes: Agreed to generalize to all sequences 20/05: Closed. Move to work item

No	Item	target version	status
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
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
027	Calendar schemes	034
032	Floating components
033	Changes from action 020 and 027 - renaming properties etc
035	Remove unorderedInitiated, add initiated content (a041)
036	Update dfdl schema with change properties (Suman)
037	Infoset text codepage
038	Improve length section