How to evaluate dynamic XPath expression in BPEL?

Question

I have an xml file where I keep many settings for my BPEL process. At runtime, I read the file and I want to select values from it based on values in the process payload.
For example, imagine that the process payload is an order:
<order>
<header>
<id/>
<customer_id/>
<team_id/>
</header>
<items>
<item>
<id/>
<sku/>
<price/>
<quantity/>
</item>
</items>
</order>
Now, in my xml settings file, I have a section where I keep a mapping of "team_id" and "assignment_group", so that for each team id, I can select the appropriate group to whom a task should be assigned. The relevant section of the settings file will look something like this:
<assignment_groups>
<group team_id='0923230'>invoice_approvers</group>
<group team_id='3094303'>order_approvers</group>
<group team_id='3434355'>shipping_approvers</group>
</assignment_groups>
So, imagine I get an order input to my process where the team_id is '3094303'. Now I have to lookup the correct assignment group in my settings file.
So, I construct the dynamic XPath expression
/settings/assignment_groups/group[@team_id=3094303]
I know that this would evaluate to "order_approvers". However, even though I have the XPath expression in a BPEL variable, and I have my settings file as a BPEL variable also, I don't know how to execute the XPath expression against the settings BPEL variable to retrieve the correct value.
Any ideas appreciated.
Thanks,
Jack

Answer 1

James:
Thank you for the response. Incidentally, this is the very same document and section that I have been looking at for guidance. Specifically, the section titled "Dynamically indexing by Constructing an XPath at Run Time" on page 12-13.
I tried to do something similar to the example at the top of page 13:
<variable name="iterator" type="xsd:integer"/>
<assign>
<copy>
<from expression="concat('/invoice/line-item[',bpws:getVariableData('iterator'), ']/line-total')"/>
<to variable="xpath"/>
</copy>
<copy>
<from expression="bpws:getVariableData('input', 'payload',bpws:getVariableData('xpath')) + ..."/>
</copy>
</assign>
I am able to achieve the first copy operation to get my dynamic XPath into a BPEL variable and that's fairly straightforward. But I am unable to get the second copy to work. Specifically, I am not sure what to put in the second argument of the bpws:getVariableData function. I have tried many different combinations, but when I try to compile my program, I get the following compilation error:
Error:
[Error ORABPEL-10902]: compilation failed
[Description]: in "C:\code\TrainingWS\SampleGetSettings\bpel\SampleGetSettings.bpel", XML parsing failed because "org.collaxa.thirdparty.jaxen.expr.DefaultFunctionCallExpr".
[Potential fix]: n/a.
Thanks,
Jack