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1 Nils, defaults and unparsing
The semantics need clarifying

I have reorganized the table

Logical Value
initiator region contains
content region contains
Nil
(implies nillable)
nilValueInitiatorPolicy
'prohibited'
empty
representation of nil
nilValueInitiatorPolicy
'required'
initiator string
"" (empty string)
(type is xs:string or xs:hexbinary)
missingValueInitiatorPolicy
'prohibited'
empty
empty
missingValueInitiatorPolicy
'required'
initiator string
missing
useNilForDefault
nilValueInitiatorPolicy
'prohibited'
empty
representation of nil
nilValueInitiatorPolicy
'required'
initiator string
default is empty string
(type is xs:string or xs:hexBinary)
missingValueInitiatorPolicy  
'prohibited'
empty
empty
missingValueInitiatorPolicy
'required'
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



Note: If nilValue is the empty string then missingValueInitiatorPolicy is not used.


Other changes:

missingValueInitiatorPolicy Enum
Valid values ‘required', ‘prohibited'

Specifies whether to expect an initiator when an element is missing. Ignored unless dfdl:initiator is specified and is not "" (empty string).

'required'- Indicates that the dfdl:initiator followed by empty content is the required syntax to indicate that the element is missing.
 
‘prohibited' - Indicates that empty content is the required syntax to indicate that the element is missing. The presence of an initiator implies that real content must follow.

Use of ‘prohibited' implies an ordered sequence. If used on an initiated element of an unordered group it is a schema definition error.

If the element is required, defaulting occurs as defined above.
This property also applies on unparsing, when the data to be written (after nil value and default value processing) is empty content.
Annotation: dfdl:element (string or hexbinary)





2 dfdl:choiceKind 'fixedLength'

The main issues  are:
a) The calculation of the length of the longest branch is not obvious.
b) The length units to use - the dfdl:lengthUnits property does not exist on a choice
c) The name could be better

Proposal is therefore to retain the property but to:
i) State the conditions that must apply to use this property, and enforce them in the validator => schema definition error otherwise
ii) Decouple the choice from its parent by calculating the length of each branch based solely on the properties of the branches components, irrespective of any parent dfdl:lengthKind

3 dfdl:occursCountKind 'expression'

When dfdl:occursCountKind is 'expression' the occursCount should only be used when parsing. On unpasring the number of occurrences is specified by minOccurs etc
 
Note this behaviour is different from dfdl:lengthKind.


4 Unsigned decimal

Whether a logical type is signed or not is used to determine whether a sign is output in some representations. However there isn't an unsigned decimal or integer so these will always be output with a sign so COBOL declarations such as
05  CFCFDN-FLD12             PIC  9(05)V99 COMP-3.

cannot be supported.

Proposed solution:

- Allow xs:nonNegativeInteger which enables unsigned unbounded integers to be modelled.  The problem to solve is then just for xs:decimal.

- Call the new property dfdl:decimalSigned. It only applies to xs:decimal or user defined restrictions thereof.  It applies to all physical decimals, as its name implies (not just zoned or packed).


We considered added a dfdl:unsignedDecimal type but rejected it as causing confusion between dfdl type restrictions and user restrictions.

5 dfdl:separatorPoilicy.

dfdl:separatorPolicy enumeration definitions are not complete as they do not discuss arrays or defaulting.

separatorPolicy="required"
No group member, except for required members with a default,  may be omitted from the data stream.
Every group member must have a separator in the correct position.
Optional members and variable-occurrence arrays will be allowed, separators will be expected for all maxOccurs
** It is a schema definition error if maxOccurs="unbounded" for any member of the group

separatorPolicy="suppressed"
Any group member ( optional or required with a default) can be omitted from the data stream, in which case its separator must also be omitted.

For prefix and infix, if a separator is found then another group member is expected.
For postfix, if enclosing markup is not found immediately after a postfix separator then another group member is expected.

Enclosing markup or end of data can occur where an infix or prefix separator is expected. This terminates the group.
Enclosing markup or end of data can occur immediately after a postfix separator (if dfdl:documentfinalSeparatorCanBeMissing is 'yes' then the postfix separator may be missing at the end of the datastream). This terminates the group.

If the group terminates before all of its members have been parsed then any required members in the remainder of the group must be defaulted into the infoset.
The entire group can have a zero-length representation, which is indicated by enclosing markup at the start of the group's content region.

If another group member is expected and the next group member is a point of uncertainty then the identity of the next group member must be determined
by resolving the point of uncertainty as described in section XXX.

If another group member is expected but no group member is found in the data stream then it is a processing error.
If another group member is expected but all group members have been parsed then it is a processing error.

separatorPolicy="suppressedAtEnd"
suppressAtEnd has the same rules as 'required' up to the last required member that does not have a default, then it has the same rules as 'suppressed'

Open questions
1. If a group has separatorPolicy='required' and one of its optional members has a zero-length representation, and that member is allowed to have a zero-length representation, what should the parser do?  
A similar question arises for required, defaultable elements with a zero-length representation when they are based on a type with xs:minLength="0". Should the default value be used, or the empty string?
2. How should the occursXXX properties be applied when there are other ways to determine the number of occurences ( e.g. by counting separators )?
3. What algorithm should the parser use to decide whether to default a complex element or group ( when the element/group is a child of a separated group)?
4. How does unparsing work for separated groups in all of these scenarios?

6 Current Actions




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
09/12: no update
16/12: reminded dent to project manager
23/12: SH will send another reminder.
06/01: Another reminder will be sent
13/01: no update
20/01: no update
27/01: no progress
29/01: no progress
03/02: IBM is still investigating
10/02: IBM is still investigating
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 progressin
084
Check behaviour of dfdl:inputValueCalc and outputValueCalc.
085
ALL: publicize Public comments phase to ensure a good review..
086
AP: Nils and Defaults during unparsing - update table
 
Regards
 
Alan Powell
 
Development - MQSeries, Message Broker, ESB
IBM Software Group, Application and Integration Middleware Software
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