[DFDL-WG] Variable definitions in the defineFormat block

[Suman Kalia]

Alan/Steve -  Changes after our meeting this morning (June 16, 2009) 

Define a variable format block just like we define textNumberFormat. The 
variable block could be at schema level but preferably should be defined 
within the defineFormat definition so that  variables are scoped to format 
definition and do not pollute the schema namespace.. 
Variable block is referenced from dfdl:format annotation just like 
textNumberFormat block is referenced through textNumberFormatRef 
annotation.

It addresses the problem hilited today in the meeting related to semantics 
of dfdl:ref="myFormat" annotation on a xsd constructs. The net effect of 
this annotation is as if the dfdl:format annotation (along with the 
attribute settings) is specified explicitly on the xsd construct.  By 
providing a level of indirection and referencing variable block through 
varRef annotations, we have permitted visibility to variables but not to 
the definition of variables. 

Excerpts from MyEnvelopeFormat.xsd - attached for perusal.. Also attached 
is the    PI for the example ( see updated xsd files under the folder 
enveloper_skk) 

        <xsd:annotation>
                <xsd:appinfo source="http://dataformat.org/">
                        <dfdl:defineFormat name="MyEnvelopeFormat" 
baseFormat="dfdlDefaultFormat:defaultFormat" >

                                <!--  statically override properties 
specific to the envelope wrapped messages -->
                                <dfdl:format byteOrder="big-Endian"   
varRef="./MyEnvelopeFormatVariables"/>

                                <!--
                                          Identify variables for 
processing the messages wrapped in an envelope
                                          i.e. the set of properties 
values that I need to take from input data and 
                                          dynamically set the values of 
dfdl properties during the processing of the message.
 
                                          Assumption: Names of variables 
defined in the format are unique
 
                                -->
 
                <!--  Define the variables needed for the format locally 
in the format block       -->
               <!--  They could also be defined at the schema level and 
referenced through varRef -->
               <!--  as its definition is QName just like textFormatBlock 
or numberFormatBlock    -->
               <!--  Best practice would be to constraint the variable 
block locally              -->
 
              <dfdl:defineVariableBlock name="MyEnvelopeFormatVariables">
                                <dfdl:defineVariable name="sep" type=
"string" />
                                <dfdl:defineVariable name="enc" type=
"string" />
                                <dfdl:defineVariable name=
"outputDirPathSep" type="string" default="/" use="output" />
                                <dfdl:defineVariable name="outputMsgKind" 
type="string" use="output" />
                                <dfdl:defineVariable name="inputMsgKind" 
type="string" use="input" />
              </dfdl:defineVariableBlock>
 
                        </dfdl:defineFormat>
                </xsd:appinfo>
        </xsd:annotation>


Suman Kalia
IBM Toronto Lab
WMB Toolkit Architect and Development Lead
WebSphere Business Integration Application Connectivity Tools 

http://www.ibm.com/developerworks/websphere/zones/businessintegration/wmb.html


Tel : 905-413-3923  T/L  969-3923
Fax : 905-413-4850 T/L  969-4850
Internet ID : kalia at ca.ibm.com
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