Aliases: [ Type of person by activity, Types of person by activity, Types of person classified by activity ]
A collection of collections. Each instance of type of person classified by activity is a collection of Persons that classifies people by some kind of activity that they do on a regular basis. Examples include student, tourist, and horn player. If the differentiating activity is one that is normally done as a career or job, it is preferable to make the collection an instance of the more specific type of profession (q.v.).