dvd example - get process instance from order id question

[jbpmndc]

In the dvd example a process instance is retrieved using an entity bean's id. Is jBPM aware of all entity beans or how is it aware that there is a process that has an orderId of x value?

ProcessInstance pi = (ProcessInstance) context.getSession()
 .createQuery("select pi from LongInstance si join si.processInstance pi " +
 "where si.name = 'orderId' and si.value = :orderId")
 .setLong( "orderId", order.getOrderId() )
 .uniqueResult();

[jbpmndc]

You would think the process definition would need to define the variables and the code would need to set the variable values:

contextInstance.setVariable("orderId", "20")

So I can't figure out when and/or where orderId is being set that allows the above query to work.

[jbpmndc]

This query takes place in the ShowOrdersAction bean. I don't see the table LongInstance in the data model for jBPM:

http://wiki.jboss.org/wiki/Wiki.jsp?page=Jbpm31DataModel

Has anyone had any success in piecing this together?

[jbpmndc]

Is this a case where I need to read the docs again or has no one encountered how this works?