How to create an activity variable?

Hi there,

I am working with Shark 1.0 and I would like to create an activity
variable "on the fly". I have seen that there is a method in order to do
this in RepositoryPersistenceManager interface but I do not know how to
get a reference to the implementation of this interface. All that I have
found are internal references, is there any way to use this or another
thing to create and remove and activity variable?

Thank you.

Best regards.

David Simon.