Given the set of all actors in this association and the target, is their
a significant difference between the population of the destination actor
in the set of all references over the relation in the candidate association
compared to over the entire relation.
Initializes a clique - add an actor and initialize the intersection
HashSet to all destinations this object links to (by keeping a set of all
actors that are linked to by all actors in a clique, determining whether
a new actor belongs is O(n) with the size of the clique for actors in the
set and constant for those not.)
Starts the database
Creates a database connection at the directory 'directory' with database
name 'database'
aquires the graph id of the root graph
compiles all the prepared statements used in the class