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(a)uk.ibm.com
Tel: +44 (0)1962 815073 Fax: +44 (0)1962 816898
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