[DFDL-WG] Minutes for OGF DFDL Working Group Call, July 21-2010

Thu Jul 22 11:39:35 CDT 2010

Open Grid Forum: Data Format Description Language Working Group

OGF DFDL Working Group Call, July 21-2010

Attendees
Steve Hanson (IBM) 
Alan Powell (IBM) 
Stephanie Fetzer (IBM)
Tim Kimber(IBM) 

Apologies
Mike Beckerle (Oco)
Suman Kalia (IBM)

1. Current Actions 
Updated below 

2. Alignment of children when forward references. 
Expressions with forward references require caching of serialized output 
which is difficult when children have alignments that are greater that 
their parent. 
Agreed that 'the alignment of a child must be less than or equal to the 
alignment of its parent'. This allows serializing parts of the tree 
without having to redo alignments. 

3. teston/testoff dfdl expression functions.
Are these functions still needed. They were introduced to allow individual 
bits to be set in a byte. Steve to look at TLog and ISO 8583 formats that 
use existence flags to see if they are still required.

Meeting closed, 16:30

Next call  Wednesday  28 July  2010  15:00 UK  (10:00 ET)

Next action: 108
Actions raised at this meeting

No
Action 
106
2. Alignment of children when forward references. 
Expressions with forward references require caching of serialized output 
which is difficult when children have alignments that are greater that 
their parent. 
Agreed that 'the alignment of a child must be less than or equal to the 
alignment of its parent'. This allows serializing parts of the tree 
without having to redo alignments. Closed
107
3. teston/testoff dfdl expression functions.
Are these functions still needed. They were introduced to allow individual 
bits to be set in a byte. Steve to look at TLog and ISO 8583 formats that 
use existence flags to see if they are still required.

Current Actions:
No
Action 
066
Investigate format for defining test cases
25/11:IBM to see if it is possible to publish its test case format.
04/12: no update
...
17/02: IBM is willing in principle to publish the test case format and 
some of the test cases. May need some time to build a 'compliance suite'
24/03: No progress
03/03: Discussions have been taking place on the subset of tests that will 
be provided.
10/03: work is progressing
17/03: work is progressing
31/03: work is progressing
14/04: And XML test case format has been defined and is being tested.
21/04. Schema for TDML defined. Need to define how this and the test cases 
will be made public
05/05: Work still progressing
12/05: Work still progressing
02/06: Work still progressing on technical and legal considerations
...
21/07: work continues
085
ALL: publicize Public comments phase to ensure a good review..
14/04: see minutes
21/04: Press release, OMG and other standards bodies.
05/05: Alan and Steve H have contacted other standards bodies. Will ask 
them to add comments on spec
15/05: still no public comments
02/06: No public comments
16/06: Public comments period has ended with no external comments. Alan 
had posted changes made in draft 041. Steve suggested send a note to the 
WG highlighting these changes.  Steve also suggested requesting an 
extension as other IBM groups may review. We discussed whether this was 
necessary as changes will need to be made during the implementation phase 
anyway. Alan to ask OGF what the process is for changes post public 
comment.
23/06: Still no comments. Alan will contact OGF to understand the rest of 
the process.
30/06: Alan has emailed Joel asking what the process is now public comment 
period is over andcan we update the published version with WG updates. No 
response yet.
07/07: No response. Alan will chase up
14/07: No response from Joel. Sent email to Greg Newby by no response.
21/07: Still no response.
086
AP: Nils and Defaults during unparsing - update table
31/03: TK to documetn use cases for parsing
14/04: Investigate new property to control empty string behaviour.
21/04: After investigation a new property is not required. New rules 
developed and tables updated.
Need examples of complexTypes to confirm tables apply. 
Review Nils, defaulting spec section.
05/05: Discussed defaulting complex elements. Tables updated but need to 
add terminator.
SH; to confirm WMD behaviour when infoset item has no value on unparsing
Need to describe defaulting choices.
15/05: More discussion. Alan updating sections
26/05: Discussed draft updates. Stephanie to confirm asserts do not make 
an element required. 
Alan will update draft..  All: review rest of draft.
02/06: Alan updated description. Please review.
Discussed Stephanie's example using discriminators. Decided no changes 
needed.
16/05: went through Steves comments. Steve to update draft.
23/06: Steve's updates to the rules discussed. See minutes. Rest of 
document needs updating.
30/06: Discussed Alans updates. Some corrections. Alan will send out 
updated copy for review before next call.
07/07: Discussed Alan updates and Tim and Steve's comments. Still some 
corrections and updates.
14/07: Discussed Alan updates (v9) Still some corrections and updates.
21/07: Discussed Draft 10. Shouldn't mention input/outputValueCalc in this 
section. Mention defaulting in calculated values section.
Move details of nilValue from nilKind property.
099
Splitting the specification in simpler sections.
07/07: Steve sent a proposal but not discussed. Alan will arrange a 
separate call.
14/07:Discussed Steve's proposal and Suman's and Alan's comments.
Need to add choice, validation, facets.
Also how does an implementation declare which subsets it supports. 
Suggested levels and/or profiles. Steve highlighted a problem when a DFDL 
schema from an implementation of just the core functions was moved to a 
full DFDL implementation what should happen about the missing properties. 
Does the full implementation need to be aware of subsets of functions? 
Should it raise a schema definition error for use of a function not in the 
subset. 
21/07: no progress
101
Semantics of 'fixed' 
21/07: Discussed whether not matching the 'fixed' value should be a 
validation error or processing error. Decided that for consistency it 
should be a validation error.
It would be useful however to avoid having to duplication of facet 
information in an assert which could become unwieldy for, say, a large 
enumeration.
Suggestions
- a parser option that 'converted all validation errors to porcessing 
errors'
- a dfdl expression function that  'applied all facets' or 'applied 
specific facet' to a particular element.
Stephanie will proce some examples of how this could be used.
102
Clarify the specification of error reporting from a DFDL processor 
- section 2.3 needs to be updated 
21/07: Section is not clear. Alan will update.
103
Asserts and discriminators 
- specify the scope of forward references. Must be downward-only. The 
expression must be resolvable by the time the component on which it is 
positioned goes out of scope - otherwise it is a processing error. 
21/07: Agreed 
104
Expressions 
Discuss error behaviour when evaluating an expression in various contexts 
- All properties: 
wrong type returned : schema definition error 
exception when evaluating expression : schema definition error 
referenced variables/paths not available : schema definition error 
- Properties which allow a forward reference 
referenced variables/paths not available : no error. DFDL processor 
continues processing until the expression result is available, then acts 
on the result. 
21/07: Steve stated the current definition that returning the incorrect 
type was a schema definition error and everything else was a processing 
error.
107
teston/testoff dfdl expression functions.
Are these functions still needed. They were introduced to allow individual 
bits to be set in a byte. Steve to look at TLog and ISO 8583 formats that 
use existence flags to see if they are still required.

Closed actions
No
Action 
105
Grammar for DFDL expression 
- currently allows multiple predicates on a single expression. Sounds as 
if this was unintended. 
21/07: Current definition is incorrect: Will delete predicateList from the 
grammar and replace with predicate. Closed
106
2. Alignment of children when forward references. 
Expressions with forward references require caching of serialized output 
which is difficult when children have alignments that are greater that 
their parent. 
Agreed that 'the alignment of a child must be less than or equal to the 
alignment of its parent'. This allows serializing parts of the tree 
without having to redo alignments. Closed

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

not started
012
Reordering the properties discussion: move representation earlier, improve 
flow of topics 

not started 
036
Update dfdl schema with change properties 
ongoing

042
Mapping of the DFDL infoset to XDM 
none
not required for V1 specification
070
Write DFDL primer 

071
Write test cases.

083
Implement RFC2116

105
AP: Describe trailingSkipBytes for delimited formats.
Alan suggested 'dfdl:terminator must be specified and not empty if 
dfdl:lengthKind is delimited or endOfParent.'

106
AP: Skip Bytes should allow bits
Ageed that it should be possible to specify bits.
- LSB and TSB renames to dfdl:leadingSkip, dfdl:trailingSkip
- units are specified by dfdl:alignmentUnits.

107
Remove timing from dfdl:assert

108
AP: Confirm behaviour of defaulting with various occursCountKinds and 
separator policies.
30/06: Decided that defaulting for variable occurrence arrays should 
always be to minOccurs. If separatorPolicy is 'required' then just the 
separators will be output up to maxOccurs and unbounded is an error.

109
define semantics of choiceKind 'fixedLength' 
dfdl:choiceKind becomes dfdl:choiceLengthKind with emuns 'implicit' 
(length of selected branch) and 'explicit' ( length specified by 
dfd;choiceLength)
New property dfdl:choiceLength 

110

nilIndicatorPath and nilIndicatorIndex properties
14/07: As part of nils default discussion the WG decided to drop 
dfdl:nilIndicator and dfdl:nilIndicatorIndex 

111
AP: using textStringPadCharacter with charRef '%#r' on multi-byte encoding 

14/07: Although there was some merit in having separate textPadKinds it 
was felt it was too late to make the change. The property descriptions 
(for numbers, calendars and booleans as well) will be improved. Closed

112
Alignment enumerations when dfdl:lengthUnits = 'bits' 
When alignmentUnits='bits', the rule that alignment must be 1,2,4,8 etc or 
multiple of 2 looks rather hard to justify. 
It was agreed to remove the restriction on aligmentUnits for both 'bytes' 
and 'bits'. Closed

113
Grammar for DFDL expression 
- currently allows multiple predicates on a single expression. Sounds as 
if this was unintended. 
21/07: Current definition is incorrect: Will delete predicateList from the 
grammar and replace with predicate. Closed

114
2. Alignment of children when forward references. 
Expressions with forward references require caching of serialized output 
which is difficult when children have alignments that are greater that 
their parent. 
Agreed that 'the alignment of a child must be less than or equal to the 
alignment of its parent'. This allows serializing parts of the tree 
without having to redo alignments. Closed

Regards

Alan Powell

Development - MQSeries, Message Broker, ESB
IBM Software Group, Application and Integration Middleware Software
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