Question

What is the pass by reference and Pass by value rules matrix between BPD and Services in IBM BPM?

Answer 1

it depends on the type of variable and also from and to whether it is a BPD or service

From	To	Type	Pass by
BPD activity	Service	Simple	Value
BPD activity	Service	Complex	Value
BPD activity	Linked BPD	Simple	Value
BPD activity	Linked BPD	Complex	Reference
Service	Nested service	Simple	Value
Service	Nested service	Complex	Reference

If you don't want to affect the original value, if it is a pass by reference, you can make a deep copy by serializing the complex variable and de-serializing it and then storing in in a new variable.

Comments

There is another concept besides Pass By Value and Pass By Reference, it is the "Pass By Value with Reference".

This comes into picture for the Shared Business Objects.

Please consider the below scenario.
For example, a shared object is passed by value with reference from a process to two different services. The process and services each contain a separate copy of the business object. When the first service completes, the shared object values are automatically persisted to the data store. When the second service starts, the shared object values are automatically loaded from the data store. So even though the process and the two services reference separate objects, the values of these objects are updated by the data store and the services operate on current data.