The xAPI state standard allow any type of activity ID, not only
integers. However, the default state store uses itemid to identify the
component instance so the activity id is limited to numerics. The store
base calls should use string as activityid as this is how xAPI specs
describe it. However, if a plugin want to use non numeric activity ids
it must implement it's own state store.
The restored states should be treated differently, to avoid resetting
them by default the first time users access them.
In that case, the first time users access to content with restored
xAPI states, they should be displayed (instead of resetting them).
Laurent David