[DFDL-WG] Minutes for OGF DFDL Working Group Call, May 05-2010 - simple infoset item with no value.
Steve Hanson
smh at uk.ibm.com
Fri May 7 05:08:35 CDT 2010
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 at uk.ibm.com,
tel +44-(0)1962-815848
From:
Alan Powell/UK/IBM at IBMGB
To:
dfdl-wg at 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 at 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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