Alan

"- It was agreed that on unparsing a simple infoset item with no value will be treated the same as missing.  Steve H to check WMB behaviour. Need to state in 4.1.2 Infoset that value is optional. "

Something to note. We say that for a simple element infoset item [dataValue] has a value (either type compliant or nil) and for a complex element infoset item [dataValue] has 'no value'.  Also  we say that for a simple element infoset item [children] has 'no value' and for a complex element infoset item [children] it may have a value (so it could also have 'no value').  The implication therefore is that an element infoset item is deduced to be simple or complex based on the [dataValue] property.  If we let a simple item take 'no value' for [dataValue] as proposed, then there is no reliable way to identify an element infoset item as simple or complex.  

Is that a problem in practice?  After parsing, all simple items will have [dataValue] set.  For items created by some other means, and presumably destined for unparsing, you could have an item with neither [dataValue] nor [children] set.  We could say (1) that an element infoset item is known to be simple or complex only when it is processed by the unparser, at which point the item is matched to the DFDL schema and its type resolved.  This is what broker's MRM parser does.  Alternatively (2) we introduce a simple/complex flag.

Note that I tried creating an MRM 'infoset' item for a string element but just gave a name and no value. The MRM serializer looked at the element, matched it to its model, found it was simple, and treated the value as NULL which invoked null processing.  The XML serializer also assumed NULL.

Personally I think we should adopt (1) but interpret 'no value' for a simple item as nil and not missing.

Regards

Steve Hanson
Strategy, Common Transformation & DFDL
Co-Chair, OGF DFDL WG
IBM SWG, Hursley, UK,
smh@uk.ibm.com,
tel +44-(0)1962-815848


From: Alan Powell/UK/IBM@IBMGB
To: dfdl-wg@ogf.org
Date: 06/05/2010 18:12
Subject: [DFDL-WG] Minutes for OGF DFDL Working Group Call, May 05-2010
Sent by: dfdl-wg-bounces@ogf.org





Open Grid Forum: Data Format Description Language Working Group

OGF DFDL Working Group Call, May 05-2010

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

Apologies
Steve Marting (Progeny)
Mike Beckerle (Oco)


1. DFDL Specification status

Alan had contacted an automotive standards body (AIAG) to generate interest in getting comments. The request had been forwarded to a number of OMG groups some of whom have at least looked at the specification. He will encourage them to make comments.

Steve H had commented on the OMG MDMI site that the DFDL spec was available

2 Nils, defaults and unparsing  

Alan had distributed tables and examples for defaulting complex elements. Steve H had updated the tables.

-  emptyValueDelimiterPolicy does apply to complex elements.
- on parsing a complex element is empty if its content region is empty. That is there no child delimiters or content.
- on unparsing defaulting occurs if a complex item is missing or present present but has no children.

Defaulting for complex elements on parsing
initiator region
content region
infoset contains
matching
Not empty
default exists for any missing required children
complex element with child elements (real & default values)
matching
empty
default exists for any required children
emptyValueDelimiterPolicy
must be
initiator or both
complex element with child elements (real & default values)
empty
Not empty
default exists for any missing required children
Initiator must not be specified
complex element with child elements (real & default values)
empty
empty
default exists for any required children
emptyValueDelimiterPolicy
must be
none
or
Initiator must not be specified
complex element with child elements (real & default values)




Defaulting for complex elements on unparsing
infoset contains
initiator region contains
content region contains
not supplied

supplied but with no children

supplied with some children
default  exist for all missing required children and final representation of complex element is empty string
emptyValueDelimiterPolicy
none
or
Initiator is not  specified
empty
empty
emptyValueDelimiterPolicy
initiator or both
initiator string
default values exist for all missing required content and final representation of complex element is  not empty string
Initiator is not specified
initiator string
 representation of complex element and its children
Initiator is not specified
empty



- The tables need to add terminator which may make them too cluttered
- It was agreed that on unparsing a simple infoset item with no value will be treated the same as missing.  Steve H to check WMB behaviour. Need to state in 4.1.2 Infoset that value is optional.

- Conformed that emptyValueDelimiterPolicy only applies is initiator or terminator is set.

- Need to describe defaulting of choices.

- Confirmed that a separator is inserted/expected when postfix separator and supressedAtEnd.

3. Current Actions:
Updated below

4 AOB

The IBM team had questioned whether timezones should be just UTC+/- offset or should GMT and other short time zones be allowed. Alan to investigate

Tim also questioned the teston/off functions. Alan stated that setting bits in a array was not possible. Will look at ISO8583 to see if needed.

Meeting closed, 14:10

Next call  Wednesday 12 May  2010  13:00 UK  (8:00 ET)

Next action: 092

Actions raised at this meeting
No
Action
091
The IBM team had questioned whether timezones should be just UTC+/- offset or should GMT and other short time zones be allowed. Alan to investigate

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
084
Check behaviour of dfdl:inputValueCalc and outputValueCalc.
14/04: no prorgess
21/04: no progress
05/05: 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.
05/05: Alan and Steve H have contacted other standards bodies. Will ask them to add comments on spec
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.
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
091
The IBM team had questioned whether timezones should be just UTC+/- offset or should GMT and other short time zones be allowed. Alan to investigate

Closed actions
No
Action
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
05/05: Subsumed into action 086 defaults.
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
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.
100
Need to state in 4.1.2 Infoset that value is optional.

 
Regards
 
Alan Powell
 
Development - MQSeries, Message Broker, ESB
IBM Software Group, Application and Integration Middleware Software
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Phone: +44-1962-815073
e-mail: alan_powell@uk.ibm.com


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