[DFDL-WG] Minutes for OGF DFDL Working Group Call, July 07-2010
Steve Hanson
smh at uk.ibm.com
Fri Jul 9 03:42:43 CDT 2010
Alan
I've made a couple of changes to item 3 to reflect what was discussed.
Regards
Steve Hanson
Strategy, Common Transformation & DFDL
Co-Chair, OGF DFDL WG
IBM SWG, Hursley, UK,
smh at uk.ibm.com,
tel +44-(0)1962-815848
From:
Alan Powell/UK/IBM at IBMGB
To:
dfdl-wg at ogf.org
Date:
08/07/2010 16:08
Subject:
[DFDL-WG] Minutes for OGF DFDL Working Group Call, July 07-2010
Sent by:
dfdl-wg-bounces at ogf.org
Open Grid Forum: Data Format Description Language Working Group
OGF DFDL Working Group Call, July 07-2010
Attendees
Steve Hanson (IBM)
Alan Powell (IBM)
Stephanie Fetzer (IBM)
Tim Kimber(IBM)
Suman Kalia (IBM)
Apologies
Mike Beckerle (Oco)
1. Current Actions
Updated below
2 Nils and Defaults.
Discussed Alan updates and Tim and Steve's comments. Still some
corrections and updates. Needs to have a introductory paragraph.
3 DFDL property types and other issues.
Not discussed
Tim has proposed more specific types for some properties. In particular
separating the different kinds of entities.
- Modify the meaning and usage of the type 'DFDL String Literal' and
modify the remainder of the specification accordingly
- Improve the description of DFDL entities to avoid confusion over the
intended usage of raw byte values.
- Clarify the standard sentence about forward references in DFDL
expressions - the current text implied that the restrictions only applied
to the unparser.
On parsing: No forward references allow for expressions that provide
property values. Asserts and discriminators may have downward references
(need to be defined)
and expression must be evaluated by the time the element has been
processed.
On unparsing: outputValueCalc may have a forward reference.
1.1 DFDL Properties
Properties on DFDL annotations may be one or more of the following types
· DFDL string literal
The property value is a string that represents a sequence of literal bytes
or characters which appear in the data stream.
· List of DFDL string literals
The property value is a space-separated list of DFDL string literals. When
parsing, if more than one string literal in the list matches the portion
of the
data stream being evaluated then the longest matching string literal in
the list must be used.
When unparsing, the first string literal in the list must be used.
· DFDL expression
The property value is an DFDL subset XPath 2.0 expression that returns a
value derived from other property values and/or from the DFDL infoset.
· DFDL regular expression
The property value is a regular expression that can be used as a pattern
to calculate the length of an element by applying that pattern to the
sequence
of literal bytes or characters which appear in the data stream.
· Enumeration
The property value is one of the allowed values listed in the property
description.
· Logical Value Simple Type
The property value is a string that describes a logical value. The type of
the logical value is one of the XML Schema simple types.
· QName
The property value is an XML Qualified Name as specified in “Namespaces in
XML “.
Identify which properties can be a list of an above type, or a union of
more than one of the above types
List: It is possible for some properties to be a list of DFDL string
literals or Logical Values. The property value is a space-separated list
of the specified type. When parsing, if more than one string literal in
the list matches the portion of the data stream being evaluated then the
longest matching string literal in the list must be used. When unparsing,
the first value in the list must be used
Union: It is possible for some properties to be a union of DFDL expression
and exactly one of the other types. If so then the expression is only
valid if it resolves to a value of the other type.
1.1.1.1 DFDL Entities in String Literals
XML entities should not be listed as they are valid in any property value.
A statement concerning use of XML entities should be added to section 5 of
the spec, if not already there.
1.1.1.1 Character classes in DFDL String literals
1.1.1.1 Raw byte values in DFDL String Literals
4. using textStringPadCharacter with charRef '%#r' on multi-byte encoding
Not discussed
textStringPadCharacter
DFDL String literal
The padding character or byte value that is used when justifying or
trimming text elements.
A pad character can be specified using DFDL entities.
A pad byte value must be specified using the %#r entity.
DFDL validation rules
- if a pad byte value is specified when lengthUnits='characters' then the
encoding must be a fixed-width encoding.
- if a pad character is specified when lengthUnits='bytes' then the pad
character must be a single-byte character.
If a pad byte value is specified when lengthUnits='characters' then
padding and trimming must be applied
using an array of N pad byte values, where N is the width of a character
in the fixed-width encoding.
Annotation: dfdl:element, dfdl:simpleType
Would adding fillByte to dfdl:padChar enumeration make it clearer.
padChar is a pad character (%#r not allowed)
fillByte is a fill byte
5. nilIndicatorPath and nilIndicatorIndex properties
These properties seem a bit of an anomaly. Tim has suggested they can be
simplified.
Tim had emaled Mike with a proposal and Steve had responded with 3
alternatives
1) Leave things as they are, perhaps renaming 'nilIndicator' to
'indicator'
2) Collapse nilIndicatorPath and nilIndicatorIndex to a single property.
It means the path is repeated, but it makes nils consistent with length
and occurs. For all, you can always use a string variable to hold the
constant part of the path and concatenate with the index. And if we
improve usability in a future DFDL release, we would improve it for nils,
lengths and occurs at the same time.
3) Drop the properties for 1.0 altogether on the grounds that it is a rare
case. I've never seen such a format, but we know Mike has.
Not discussed.
Meeting closed, 17:00
Next call Wednesday 14 July 2010 15:00 UK (10:00 ET)
Next action: 100
Actions raised at this meeting
No
Action
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
16/06: work continues
23/06: work continues
30/06: work continues
07/07: 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 chance up
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.
088
define semantics of choiceKind 'fixedLength'
31/03: TK to provide definition of calculable length.
Investigate PL/I varchars and Cobol occurs dependingon.
14/04Tim had distributed a document starting the definition of calculable
length for the longest choice member.
Alan had done some investigation of COBOL occurs depending on and when
used in the working section of a program then the maximum storage was
reserved but when used in the linkage section the dependent number was
uses. We need to understand how the WMB COBOL importer deals with ODO.
21/04: Need to define 'calculable length' and WMB importer ODO behaviour.
05/05: TK: Still need definition of calculable length.
SKK: WMB COBOL imported behaviour with ODO
15/05: Suman sent an expmle of an imported Cobol ODo which suggested that
the maximum space was reserved. He will extend the example.
02/06: no progress
16/06: no progress
23/06: no progress
30/06: Alan looked at Tim's description of calculable length and suggested
that that real use case may be much simpler. If real use case is COBOL and
C importers then it would be cleaner to require the 'fixed length' to be
specified on the enclosing complex element and remove choiceKind 'fixed
length'. Ask Suman is COBOL and C importers can be enhance to provide
length on cpmplex element.
07/07: Steve had proposed 5 possible approaches to supporting main use
case.
i) Change the importer to add a parent element for each group. Con: This
changes the logical model by inserting an extra level.
ii) Allow dfdl:length to be carried on embedded xs:choice (along with
dfdl:lengthUnits & dfdl:lengthKind).
iii) New dfdl:choiceLength property to be carried on embedded xs:choice
(always bytes).
iv) dfdl:choiceKind as today. Con: length from TD model is lost and must
be recalculated.
v) dfdl:choiceKind but with limitations to make the calculation easier.
Con: length from TD model is lost and must be recalculated.
Agreed a modified version of iii)
dfdl:choiceKind becomes dfdl:choiceLengthKind with emuns 'implicit'
(length of selected branch) and 'explicit' ( length specified by
dfd;choiceLength)
New property dfdl:choiceLength
096
AP: using textStringPadCharacter with charRef '%#r' on multi-byte encoding
07/07: not discussed
097
nilIndicatorPath and nilIndicatorIndex properties
07/07: Tim had emaled Mike with a proposal and Steve had responded with 3
alternatives
1) Leave things as they are, perhaps renaming 'nilIndicator' to
'indicator'
2) Collapse nilIndicatorPath and nilIndicatorIndex to a single property.
It means the path is repeated, but it makes nils consistent with length
and occurs. For all, you can always use a string variable to hold the
constant part of the path and concatenate with the index. And if we
improve usability in a future DFDL release, we would improve it for nils,
lengths and occurs at the same time.
3) Drop the properties for 1.0 altogether on the grounds that it is a rare
case. I've never seen such a format, but we know Mike has.
Not discussed.
099
Splitting the specification in simpler sections.
07/07: Steve sent a proposal but not discussed. Alan will arrange a
separate call.
Closed actions
No
Action
092
AP: Confirm behaviour of defaulting with various occursCountKinds and
separator policies.
16/06: no progress
23/06: discussed
- whether when number of instances doesn't match specified number of
occurrences is it an error or should missing instances be defaulted?
Decided it is an error.
- defaulting occurs up to minoccurs unless separator policy is required
when default up to maxOccurs and unbounded is an error.
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.
07/07: Agreed last call's decision. 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.
Regards
Alan Powell
Development - MQSeries, Message Broker, ESB
IBM Software Group, Application and Integration Middleware Software
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