14.3 Planning with Chronicles 331
the constraints C how the world changes over time. The chronicle is interpreted
as a conjunction of temporal assertions and temporal and object constraints. The
object constraints in a chronicle are restricted to unary or binary constraints over
finite domains on object variables. These are constraints of the form x ∈ D, x = y,
x = y, conditional expressions such as “if x ∈ D
1
then y ∈ D
2
,” and pairs of
allowed values for two variables, e.g., as defined by a rigid relation. The temporal
constraints are here those of the point algebra PA. Hence, we will not instantiate
temporal variables into numerical values. Other temporal constraint formalisms
can be used in the chronicle representation; in particular, the use of