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@ca.ibm.com