A time sequence (TS) is a sequence (ordered by time) of pairs < v, t > where v is an arbitrary data object and t are chronons of a given granularity designating past and/or future instants. A TS is identified by a surrogate (possibly a time-invariant key). If each v is a single value, the TS is said to be simple, and if v is a complex value (e.g., a set, a sequence, etc.), the TS is complex. A TS may have properties and/or constraints attached to it.