To find associations of two objects 'a' and 'b' from the 3 time slices of a
hypermapped virtual world R
the query in mathematical notation is:
Sx
(x1o, x2o)
(St
(t1, t2, t3) R)
In SQL-like language the query can be expressed as:
SELECT x
CLUSTER OPEN x1, OPEN x2
FROM SELECT t
CLUSTER t1, t2, t3
FROM R