[DFDL-WG] Minutes for OGF DFDL Working Group Call, November-11-2009

[Alan Powell]

Open Grid Forum: Data Format Description Language Working Group

OGF DFDL Working Group Call, November-11-2009

Attendees
Suman Kalia (IBM)
Steve Hanson (IBM)
Mike Beckerle (Oco)
Peter Lambros (IBM)
Steve Marting (Progeny)
Stephanie Fetzer (IBM)

Apologies
Alan Powell (IBM)


1. 051 Scoping Rules 
Two issues discussed: 
a) Use of selectors
Reviewed Suman's selectors examples. Agreement that the semantic was 
correctly captured and no further action needed.
b) Default dfdl:format annotation
Rejected proposal to wrap this in an unnamed dfdl:defineFormat. All 
dfdl:definexxx should be named.

Action 51 closed.

2. 061 Refactor dfdl:textNumberFormat to remove dfdl:numberBase.
Reviewed Alan's updated spec fragment. 
Looks good, a couple of comments:
a) Suggestion to replace the enum 'text' from dfdl:textNumber 
Representation, as it is confusing because of dfdl:representation enum 
'text'. Proposals were 'plain' or 'regular'. More welcomed.
b) In dfdl:textNumberFormatRef, the clause should just say "Only applies 
when textNumberBase is '10' " for consistency with other text properties. 

Action 61 updated.

3. 059: External specification of encoding, byte order
Reviewed Steve H's proposal.
Agreed that DFDL xsd wins over context.
Agreed that $encoding & $byteOrder would be built-in 'external' variables 
in DFDL namespace.
  $encoding should have default UTF-8
  $byteOrder should have default big-endian
Rejected formal spec statement that DFDL implementation can optionally 
override DFDL xsd

Action 59 updated.

4. 045 Resolving points of uncertainty and parsing rules 
Continued discussion of semantics of discriminators and arrays, using 
Mike's example. The example has 3 levels of uncertainty. The following key 
points emerged during the web meeting.

The use of timing="after" on a 'forward looking' dfdl:discriminator does 
not always work. Because it is evaluated at the end of parsing the hosting 
component, a failure might have occurred while parsing one of the 
children. The failure will cause backtracking, even though we might have 
parsed enough to evaluate the discriminator.

The WTX equivalent (component rules on identifier fields) handles 'forward 
looking' by continually trying to evaluate the rule as it processes a 
component's children.  Conceptually timing="during". 

Mike changed the discriminators so that they were decorated, eg, 
choiceDiscriminator, occurDiscriminator. This makes what the discriminator 
applies to more obvious.  An equivalent alternative is to link the 
component and the discriminator using an id/idref, or an SCD.  Mike will 
think more on this, and also whether other decorated discriminators are 
needed, eg, for unordered/floating sequences.

Stephanie will supply equivalent WTX type tree for comparison.

It was noted that there is a big semantic difference between DFDL 
discriminators and WTX component rules - if the former's expression 
evaluates to false then a processing error is raised.  Not so with WTX, 
which will continue on. 

Action 45 updated.
Action 33 closed and merged into 45.

5. Actions
Updated below.
Note closure of action 62 which was not discussed on the call - we have 
the name of an IBM technical writer to assist with spec completion.


Next call 18 November 13:00 UK

Meeting closed, 15:00

Next action: 064
Actions raised at this meeting

No
Action 




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
...
09/06: No Progress (low priority)
17/06: SH to check ICU code for lax calendar behaviour
24/06: no progress
...
12/08: no progress
19/08: Inconsistencies are being found in ICU behaviour so Calendars need 
reviewing again.
26/08: Specific three character short time zones may not be  maintained 
during round tripping when there is more than one short form for a time 
zone offset. Because dates and datetimes in the infoset only maintain a 
time zone offset so on unparsing it isn't possible to say which short form 
will be selected for a particular offset when there is more than one 
possible. Need to document.
09/09: no progress
...
14/10: no progress
21/10: Will produce a list of known issues.
28/10: Discussed ICU farctional seconds behaviour. SF to send latest 
understanding.
04/11: no progress
11/11: no update
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
27/05: No Progress
03/06: The concern is that some dfdl schemas will fail UPA check when 
validation is turned on or when editted using tooling that enforces UPA 
checks. Renaming fields will resolve some/most issues. Need documentation 
that  describes issue and best practice.
17/06: no change
24/06: no change
01/07: no progress
...
12/08: No Progress (lower priority)
19/08: Clarify that this action is to go through the XML UPA checks to 
assess impact on dfdl schemas and advice best practice. Name clashes is 
just one example. SH or SKK
26/08: No Progress (lower priority)
09/09: no progress
...
04/11: no progress
11/11: Steve has started to look at this. He has requested a 'consumable' 
definition of the UPA rules from the XSD WG members. Even non-normative 
Appendix H in the XSD 1.0 spec is hard to consume.
045
20/05 AP: Speculative Parsing
27/05: Psuedo code has been circulated. Review for next call
03/06: Comments received and will be incorporated
09/06: Progress but not discussed
17/06: Discussed briefly
24/06: No Progress
01/07: No Progress
15/07: No progress. MB not happy with the way the algorithm is documented, 
need to find a better way.
29/07: No Progress 
05/08: No Progress. Will document behaviour as a set of rules.
12/08: No Progress 
...
16/09: no progress
30/09: AP distributed proposal and others commented. Brief discussion AP 
to incorporate update and reissue
07/10: Updated proposal was discussed.Comments will be incorporated into 
the next version.
14/10: Alan to update proposal to include array scenario where minOccurs > 
0
21/10: Updated proposal reviewed
28/10: Updated proposal reviewed see minutes
04/11: Discussed semantics of disciminators on arrays. MB to produce 
examples
11/11: Absorbing action 033 into 045.  Maybe decorated discrminator kinds 
are needed after all. MB and SF to continue with examples. 
049
20/05 AP Built-in specification description and schemas
03/06: not discussed
24/06: No Progress
24/06: No Progress (hope to get these from test cases)
15/07: No progress. Once available, the examples in the spec should use 
the dfdl:defineFormat annotations they provide.
...
14/10: no progress
21/10: Discussed the real need for this being in the specification. It 
seemed that the main value is it define a schema location for downloading 
'known' defaults from the web. 
28/10: no progress
04/11: no progress
11/11: no update
056
MB Resolve lengthUnits=bits including fillbytes
12/08: No Progress
...
28/10: no progress
04/11: MB to look at lengthUnits = bits
11/11: no update
059
9/9: SH Define how encoding,  byteorder and floating point format 
externally
16/09: no progress
07/10: no progress
14/10: no progress
21/10: SH to investigate
28/10: no progress
04/11: no progress
11/11: SH proposal accepted. One open issue - what is the full list of 
built-in variables?
061
AP Refactor dfdl:textNumberFormat to remove dfdl:numberBase. 
14/10: Base 2, 8, 16 numbers are invariably integers without formatting, 
use of pattern etc is overkill
21/10: no progress
28/10: no progress
04/11: no progress
11/11: Reviewed AP proposal, some comments to incorporate.
063
Write DFDL primer and test cases.
11/11: no update

Closed actions
No
Action 
033
MB: Need for scope indicator on discriminator
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)
27/05: No Progress (lower priority)
....
07/10: no progress
14/10: Action re-titled and assigned to Mike B
21/10: no progress
28/10: no progress
04/11: Mike to produce examples for choices with variable occurrence 
arrays.
11/11: Closed. Incorporated into action 045. 
051
Scoping rules.
MB: to document change to scoping rules to satisfy implementation concerns
17/06: MB and SH proposals discussed. Needs further discussion
24/06: AP to update presentation with latest proosal
24/06: AP had updated presentation. MB to review
08/07: Discussed at length. Simple types will now take annotations. 
Variables will be used for parameters.
15/07: No further progress. Needs final write up.
29/07: No Progress
05/08: No Progress 
12/08: No Progress 
19/08: AP will document new syntax rules.
26/08: No Progress 
09/09: AP has documented new scoping rules. Not discussed
16/09: Not disussed. AP to update element reference examples
30/09: Significant dissatisfaction with proposed new rules. New proposal 
developed during call. AP to document.
07/10: New proposal was refined. Details in minutes.
14/10: Discussed at length. Details in minutes. 
21/10: Discussed at length. Details in minutes. 
04/11: defineFormat can only contain one active format block, Drop 
baseFormat, SKK to produce examples for selectors.
04/11: Further discussion see minutes. SKK to produce examples of 
selectors.
11/11: Closed. No open questions. Incorporate into spec via work item 051.
062
SH investigate technical writer support.
28/10: SH had contacted S Gao to understand the W3 process and support. 
04/11: no progress
11/11: Closed. SH has the name of an IBM technical writer who can help 
with spec preparation - Mark Tibbits.

Work items:
No
Item
target version
status
005
Improvements on property descriptions 

not started
011
How speculative parsing works (combining choice and variable-occurence - 
currently these are separate) (from action 045)

awaiting completion of actions 045  
012
Reordering the properties discussion: move representation earlier, improve 
flow of topics 

not started 
033
Numeric data - what physical reps are allowed for what logical types (from 
action 020)
037
ensure all behaviour documented
036
Update dfdl schema with change properties 
ongoing

038
Improve length section including bit handling

some improvement in 036
042
Mapping of the DFDL infoset to XDM 
none
not required for V1 specification
051
Revised scoping rules (from action 051)
037

058
textPadCharacter %#rxx limitation and split to textxxxxPadCharacter
037

059
limit terminatorCanBeMissing to last element in schema. Ignore elsewhere.
037

060
New empty string semantic for dfdl:binaryBooleanTrueRep
037

061
Change maxOccurs violations from processing error to validation error (if 
not 'fixed')
037

062
Drop calendarUseZForUTC. describe zU, IU and TU symbols
037

063
DefineFormat can contain only one active format. Drop baseFormat
037





Alan Powell

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






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