[DFDL-WG] Action 086: Nils and Defaults for complex elements

[Steve Hanson]

Alan

I think empty must really mean empty - no sequence initiator or 
separator(s) or terminator. If you have any of those then there is 
content, the complex element is there, and you apply defaulting to the 
children. 

I struggled with the tables.  I've changed them both. 


Defaulting for required complex element on parsing 
initiator region
content region

infoset contains
matching
not empty
 default values exist for all required content
complex element with child elements (real values)
matching
empty
 default values exist for all required content
emptyValueDelimiterPolicy 
 must be 
initiator or both
complex element with child elements (default values)
empty
not empty
default values exist for any missing required content
Initiator must not be specified
complex element with child elements (real values)
empty
empty
default values exist for all required content
emptyValueDelimiterPolicy 
 must be 
none 
or 
Initiator must not be specified
complex element with child elements (default values)



Defaulting for required complex element on unparsing 
infoset contains

initiator region contains
content region contains
not supplied

supplied but with no children

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

initiator string if specified
 representation of complex element and its children

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:
30/04/2010 16:26
Subject:
[DFDL-WG] Action 086: Nils and Defaults for complex elements
Sent by:
dfdl-wg-bounces at ogf.org




Part of Action 086 is to apply the clarified Nils and Defaulting rules to 
complex elements and develop some examples. 

The tables for parsing and unparsing are simpler because there is no need 
to consider nillable. 

I have assumed 
-  emptyValueDelimiterPolicy does apply to complex elements. 
- on parsing a complex element is empty if its children's content is 
empty. That is the child delimiters may be present. 
- 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

Logical Value
matching
Not empty

parsed children
matching
empty
 A default is specified
emptyValueDelimiterPolicy 
 must be 
initiator or both
default value 
of children
empty
Not empty

Initiator must not be specified
parsed children
empty
empty
A default is specified
emptyValueDelimiterPolicy 
 must be 
none 
or 
Initiator must not be specified
default value 
of children



Defaulting for complex elements on unparsing 
Logical Value

initiator region contains
content region contains
Missing or present with no children
default of all children is empty string
emptyValueDelimiterPolicy 
 none
empty
empty
emptyValueDelimiterPolicy 
initiator or both
initiator string
default of any child is not empty string

initiator string
 representation of the child default value.
a least on child exists

initiator string
representation of children



Examples 
Defaulting Complex types 
ONE:one, 
TWO: 
   TWOONE:twoone; 
   TWOTWO:twotwo; 
   TWOTHREE:twothree, 
THREE:three 
<end> 


In the following TWO is 'empty' (when relevant dfdl properties are set) 

ONE:one,THREE:three<end>
|separatorPolicy='suppressed', emptyValueDelimiterPolicy='none'

ONE:one,,THREE:three<end>
separatorPolicy='required', emptyValueDelimiterPolicy='none'

ONE:one<end>
separatorPolicy='suppressed' or 'suppressedAtEnd', 
emptyValueDelimiterPolicy='none'

<end>
separatorPolicy='suppressed' or 'suppressedAtEnd', 
emptyValueDelimiterPolicy='none'

ONE:one,TWO:,THREE:three<end>
separatorPolicy= don't care , emptyValueDelimiterPolicy='initiator'

ONE:one,TWO:<end>
separatorPolicy= 'suppressed' or 'suppressedAtEnd', 
emptyValueDelimiterPolicy='initiator'

ONE:one,TWO:,<end>
separatorPosition='postfix'
separatorPolicy= 'suppressed' or 'suppressedAtEnd', 
emptyValueDelimiterPolicy='initiator' 

*** Should 'postfix' separator be there when 'supressedAtEnd'  *** 

ONE:one,TWO:TWOONE:,THREE:three<end>
separatorPolicy= 'suppressed' or 'suppressedAtEnd', 
(TWO)emptyValueDelimiterPolicy='initiator' 
(TWOONE)emptyValueDelimiterPolicy='initiator' 


ONE:one,TWOONE:,THREE:three<end> 
separatorPolicy= 'suppressed' or 'suppressedAtEnd', 
(TWO)emptyValueDelimiterPolicy='none' 
(TWOONE)emptyValueDelimiterPolicy='initiator' 

*** We should discuss this example. *** 
  
Regards 
  
Alan Powell 
  
Development - MQSeries, Message Broker, ESB 
IBM Software Group, Application and Integration Middleware Software 
------------------------------------------------------------------------------------------------------------------------------------------- 

IBM 
MP211, Hursley Park 
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United Kingdom 
Phone: +44-1962-815073 
e-mail: alan_powell at uk.ibm.com






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