For a table-driven rule, define the data source as Service Items and construct your data retrieval rule using the wizard. For a more complicated SQL-coded rule, just use the RequestCenter datasource, and look up the service item definition to learn the name of the physical table and columns that hold the SI data. Depending on how your SI is structured, you might also have to look at the corresponding SI Subscription table to find out which requisition or customer created the SI.
I think there may be some timing issues here, however. By invoking Service 1.1 from the Related Services tab, the values for the SI are pre-filled on the form. HOWEVER, this pre-filling might happen AFTER a data retrieval rule in the onload event attempts to execute. If that is the case, I would file a defect report with TAC.
Ok so let's say I had a field in my dictionary for the associated service (Service1.1) called parentReqId. I want to automatically populate that field in my form with the requisition id that produced the parent service (Service1).
I create a new data retrieval rule and in the wizard ...
Step 1: select "distributing rule"
Step 2: select "before the form is loaded (server-side)
Step 3: select datasource "Service Items" and ???
At this point I need to select a table name. Do I select "ServiceItemSubscription" or "ServiceItemHistory"? What is the difference between these?
I am assuming there is some relationship in the database that maintains the parent / child relationship between Service1 and Service1.1 and that relationship is created automatically by virtue of ordering the child service from the context of the parent service (i.e. clicking the order button from the "related services" tab on the "service items" page). Is that assumption incorrect?