What is the form of an @source XPath expression where the source propertyis multi-valued?

[Mike Edwards <mike_edwards@uk.ibm.com>]

Folks,

OK, here is an interesting question.

SCA component properties support a @source
attribute which indicates that the value for the property is obtained from
the value of a property of the containing
composite.  The source attribute takes the general form of an XPath
expression,
but starting with "$composite_property_name",
which indicates the name of the composite property to use, and which
logically implies the "XML document"
on which the remainder of the XPath expression operates.

For example:

    <property
name="complexType"
type="test:ComplexType1"/>
 
    <component
name="TestComposite12Component1">
         
<implementation.composite
name="test:TestComposite71"/>
        <service
name="Service1"/>
        <property
name="serviceData1"
source="$complexType/test:firstData/text()"/>
    </component>

If the composite property is multi-valued
(i.e. @many = "true"), what should be the form of the XPath expression
in the @source attribute?

    <property
name="complexType"
many="true"
type="test:ComplexType1">
     
  <value>
         
      <firstData>Sample
first data</firstData>
         
      <secondData>Sample
second data</secondData>
     
  </value>
     
  <value>
         
      <firstData>Alternate
first data</firstData>
         
      <secondData>Alternate
second data</secondData>
     
  </value>
    </property>
 
    <component
name="TestComposite76Component1">
         
<implementation.composite
name="test:TestComposite71"/>
        <service
name="Service1"/>
        <property
name="serviceData1"
source="?????"/>
    </component>

In this case, the composite property
contains an array of values.

So, does this imply that the right way
to approach this for the @source XPath expression is as follows:

$complexType        
                     
                     
      --> the whole array of values
$complexType[1]      
                     
                     
   --> the first value in the array
$complexType[n]      
                     
                     
   --> the nth value in the array

$complexType[n]/test:firstData/text()
                 --> the
text in the firstData element of the nth value in the array

and I suppose that since the [...] syntax
in XPath is actually a Predicate rather than simply an array index, this
can imply other expressions being contained
within the brackets, such as @foo="bar", which would select
the value elements in the array which
happen to have thier @foo attribute set to "bar".


I am asking this since our spec is silent
on this point and our @source expression format is not straight XPath
but has this twist of having the target
property name at its root.


Yours,  Mike.

Strategist - Emerging Technologies, SCA & SDO.
Co Chair OASIS SCA Assembly TC.
IBM Hursley Park, Mail Point 146, Winchester, SO21 2JN, Great Britain.
Phone & FAX: +44-1962-818014    Mobile: +44-7802-467431  
Email:  mike_edwards@uk.ibm.com

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