[DFDL-WG] Minutes for OGF DFDL Working Group Call, April 21-2010
Alan Powell
alan_powell at uk.ibm.com
Thu Apr 22 05:39:05 CDT 2010
Open Grid Forum: Data Format Description Language Working Group
OGF DFDL Working Group Call, April 21-2010
Attendees
Steve Hanson (IBM)
Alan Powell (IBM)
Mike Beckerle (Oco)
Stephanie Fetzer (IBM)
Tim Kimber(IBM)
Apologies
Steve Marting (Progeny)
Suman Kalia (IBM)
1. DFDL Specification status
There have been no public comments so far but this is not unexpected.
Steve H is pursuing a press release from IBM and OCO. Mike will send
updated information to the OMG.
Alan will pursue contacts from the Athena EU project.
2 Nils, defaults and unparsing
Steve H, Tim and Alan have had further discussions and concluded and new
property was not required so propose
- Elements that are zero length and elements that are 'missing' from the
data stream should be treated the same.
- missingValueInitiatorPolicy should be renamed to
emptyValueInitiatorPolicy to distinguish from a missing infoset value on
unparsing
- Any 'initiator' policy needs to also include terminators so the
enumerations should be extended to "none", "initiator", "terminator",
"both". and the properties renamed emptyValueDelimiterPolicy and
nilValueDelimiterPolicy .
The tables have been reworked
Nils and Defaults on Parsing
initiator region
content region
Logical Value
matching
content
content matches nilValue
nilValueDelimiterPolicy
must be
initiator or both
nil
Content does not match nilValue
parse content to get value
matching
empty
empty string is a nil value
nilValueDelimiterPolicy
must be
initiator or both
nil
A default is specified
emptyValueDelimiterPolicy
must be
initiator or both
default value
(may be nil, empty space or value)
empty
content
content matches nilValue
nilValueDelimiterPolicy
must be
none
nil
Content does not match nilValue
Initiator must not be specified
parse content to get value
Initiator is specified
ERROR
empty
empty
empty string is a nil value
nilValueDelimiterPolicy
must be
none
nil
A default is specified
emptyValueDelimiterPolicy
must be
none
default value
(may be nil, empty space
or value)
Note. The default value can be the empty space.
Nils and Defaults on Unparsing
Logical Value
initiator region contains
content region contains
Nil
(implies nillable)
nilValueDelimiterPolicy
none
empty
representation of nil
nilValueDelimiterPolicy
initiator or both
initiator string
"" (empty string)
(type is xs:string or xs:hexBinary)
emptyValueDelimiterPolicy
none
empty
empty
emptyValueDelimiterPolicy
initiator or both
initiator string
missing
useNilForDefault
nilValueDelimiterPolicy
none
empty
representation of nil
nilValueDelimiterPolicy
initiator or both
initiator string
default is empty string
(type is xs:string or xs:hexBinary)
emptyValueDelimiterPolicy
none
empty
empty
emptyValueDelimiterPolicy
initiator or both
initiator string
Other default
initiator string
representation of the default value.
a non-nil non-empty-string value
initiator string
representation of the logical value
The above tables (with minor changes) were agreed.
The tables currently apply to simpleTypes, examples are needed to confirm
that they are correct for complexTypes as well.
Steve questioned whether complexTypes can be nillable as WTX allow this.
Stephanie will investigate.
Subsequently Stephanie confirmed that this was only needed for XML support
in WTX so is not needed in DFDL.
The Nils, defaulting section in the spec will be reviewed/rewritten to
incorporate the new understanding.
3. Current Actions:
Updated below.
4 Expressions during Unparsing.
In order to reduce complexity and potential performance problems it is
proposed to
- nilValue and occursStopValue should NOT be able to take an expression.
Agreed
- Very few properties should be allowed to have forward references. Table
below agreed
Here's the list of properties that can take an expression, along with some
suggested restrictions on forward referencing:
byteOrder
backward reference only
encoding
backward reference only
initiator
backward reference only
terminator
backward reference only
separator
backward reference only
outputNewline
backward reference only
length
simple elements : backward reference only.
complex elements : forward reference allowed
Quote "When unparsing with dfdl:lengthKind="explicit", the calculation of
dfdl:representationLength() returns the value of the dfdl:length
property." A simple element's length needs to be known in advance, else it
cannot be parsed. A complex element's length might get resolved while
parsing its content, so a forward reference within the scope of the
complex element is possible.
Having said that, we might want to impose a restriction in IBM's DFDL
processor v1.0 that only backward references are allowed.
escapeCharacter
backward reference only
escapeEscapeCharacter
backward reference only
textNumberDecimalSeparator
backward reference only
textNumberGroupSeparator
backward reference only
textNumberExponentCharacter
backward reference only
binaryFloatRep
backward reference only
textBooleanTrueRep
backward reference only
textBooleanFalseRep
backward reference only
nilValue
backward reference only
Not clear why this needs to be specified as an expression. ( may already
be on a list of open issues somewhere )
nilIndicatorPath
backward reference only
occursCount
backward reference only
occursStopValue
Not clear why this needs to be specified as an expression.
[inputValueCalc]
[Parser only] Backward reference only
outputValueCalc
Forward or backward reference
Meeting closed, 14:10
Next call Wednesday 28 April January 2010 13:00 UK (8:00 ET)
Next action: 091
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
084
Check behaviour of dfdl:inputValueCalc and outputValueCalc.
14/04: no prorgess
21/04: no progress
085
ALL: publicize Public comments phase to ensure a good review..
14/04: see minutes
21/04: Press release, OMG and other standards bodies.
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.
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.
089
Need to be able to define unsigned decimal and integer
31/03: MB to agree proposed solution
14/04: MB to agree proposed solution
21/04: Agreed. Closed
090
Semantics of separatorPolicy
14/04: Discussion on detecting when complex types should be defaulted.
Examples needed.
21/04: Complex defaulting examples needed for new rules
Closed actions
No
Action
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
097
Remove functions that returns duration
098
occursCountKind is parsing only
099
nilValue and OccuresStopValue cannot have an expression.
On unparsing only outputValueCalc can have a forward reference.
Regards
Alan Powell
Development - MQSeries, Message Broker, ESB
IBM Software Group, Application and Integration Middleware Software
-------------------------------------------------------------------------------------------------------------------------------------------
IBM
MP211, Hursley Park
Hursley, SO21 2JN
United Kingdom
Phone: +44-1962-815073
e-mail: alan_powell at uk.ibm.com
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.ogf.org/pipermail/dfdl-wg/attachments/20100422/db72725e/attachment-0001.html
More information about the dfdl-wg
mailing list