The xAPI state standard allows any type of activity ID, not only integers.

However, the default state store (core_xapi\state_store) uses itemid to identify the component instance, so the activity id is limited to numerics.

The state store base calls should use string as activityid as this is how xAPI specs described it. However, if a plugin wants to use non-numeric activity ids, it must implement its own state store.

All core_xapi\state_store should throw an exception if the activity id is not compatible.