Introducing Asserter/Observer

Hi All,

Given the discussions around Thing (and IVPT), there has been many 
mentions of the notion of an assertor or observer. This is not part of 
our list of concepts but seems to be quite useful.

Two questions:
1) Does the group think that this should be an additional concept?

2) If it is useful, what are your thoughts on this definition:
    - an Asserter/Observer asserts a description of the provenance of 
one or more things.

Thanks,
Paul