[DFDL-WG] dfdl-wg Digest, Vol 47, Issue 1
Tim Kimber
KIMBERT at uk.ibm.com
Thu Jul 1 10:02:06 CDT 2010
re: 6.
6 Remove timing from dfdl:assert.
As timing property has been removed from discriminators it is inconsistent
to still have it on assert. Agreed
There was also a discussion about adding a message property to
discriminators which was inconclusive so decided not to change.
I remembered the reason why I thought this was a good idea.
Consider the situation where someone is generating their DFDL schema from
meta-data. The model is large, and consists of many references to global
structures. Each global structure ( e.g. an HL7 segment ) is identified in
a particular way. Sometimes the segment is required, sometimes it is not.
Sometimes it occurs as a child of a choice group, and sometimes not.
Regardless, it is highly likely that the segment will be identified in the
same way wherever it occurs. A natural decision for the modeler would be
to create a dfdl:discriminator on all references to the segement, even if
the ref is not under a point of uncertainty. It's harmless, and it carries
no performance penalty. If we disallow the "message" attribute, it will
force the modeler to put in extra logic to work out whether the ref is
under a POI, and generate an assert/discriminator as appropriate.
I'd be interested to know what Steph thinks about this - I think I've
heard her say that she sometimes uses discriminators where an assert would
have done the job, just to maintain consistency throughout the model.
regards,
Tim Kimber, Common Transformation Team,
Hursley, UK
Internet: kimbert at uk.ibm.com
Tel. 01962-816742
Internal tel. 246742
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Date:
01/07/2010 14:47
Subject:
dfdl-wg Digest, Vol 47, Issue 1
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Today's Topics:
1. Minute for OGF DFDL Working Group Call, June 30-2010 (Alan Powell)
----- Message from Alan Powell <alan_powell at uk.ibm.com> on Thu, 1 Jul 2010
14:47:07 +0100 -----
To:
dfdl-wg at ogf.org
Subject:
[DFDL-WG] Minute for OGF DFDL Working Group Call, June 30-2010
Open Grid Forum: Data Format Description Language Working Group
OGF DFDL Working Group Call, June 30-2010
Attendees
Steve Hanson (IBM)
Alan Powell (IBM)
Stephanie Fetzer (IBM)
Tim Kimber(IBM)
Apologies
Suman Kalia (IBM)
Mike Beckerle (Oco)
1. Current Actions
Updated below
2 Nils and Defaults.
Reviewed Alan's latest draft.
Agreed with definition of 'required parent context'
Preferred the combining of initiated and not initiated rules.
Would still like a separate definition of nillable
Minor editorial changes.
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.
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 describes a sequence of
literal bytes and 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 XPath 2.0 expression that calculates evaluates to
returns a value derived from other property values and/or from the DFDL
infoset. DFDL expressions can be used to calculate property values, and to
calculate logical values for simple elements.
· 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 comparing applying that pattern
to the sequence of literal bytes or characters which appear in the data
stream.
· Enum
The property value is a string literal that must be one of the allowed
values listed in the property description.
· QName
The property value is a string literal that also conforms to an XML
Qualified Name as specified in “Namespaces in XML “
· 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 in the DFDL
allowed subset.
1.1.1.1 DFDL Entities in String Literals
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.
Not discussed
6 Remove timing from dfdl:assert.
As timing property has been removed from discriminators it is inconsistent
to still have it on assert. Agreed
There was also a discussion about adding a message property to
discriminators which was inconclusive so decided not to change.
7. Splitting the specification in simpler sections.
Concern has been raised that a full DFDL implementation is complicated and
expensive.
A number of reviewer have said that they might implement only part of the
sepcification.
It has been suggested that the WG should look to see if it possible to
split the specification into more
manageable optional sections.
Meeting closed, 17:00
Next call Wednesday 07 July 2010 15:00 UK (10:00 ET)
Next action: 100
Actions raised at this meeting
No
Action
096
AP: using textStringPadCharacter with charRef '%#r' on multi-byte encoding
097
nilIndicatorPath and nilIndicatorIndex properties
099
Splitting the specification in simpler sections.
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
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.
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.
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.
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.
096
AP: using textStringPadCharacter with charRef '%#r' on multi-byte encoding
097
nilIndicatorPath and nilIndicatorIndex properties
099
Splitting the specification in simpler sections.
Closed actions
No
Action
098
Remove timing from dfdl:assert
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
Regards
Alan Powell
Development - MQSeries, Message Broker, ESB
IBM Software Group, Application and Integration Middleware Software
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