In Service Studio you can expose processes owned by your eSpace to be used by a different one. In this context, the eSpaces are called Producer and Consumer, respectively.
How to Expose a Process
In the Producer eSpace, set the Public property of your process to Yes and publish the eSpace. How?
When you expose a process its process entity will also be exposed.
In this situation, an error message is presented and the eSpace is not valid.
Use Process References | Process Properties | About Process Entities