Comparison Between Two Languages Used to Express Planning Goals: CTL and E A G LE

The extended goals in non-deterministic domains are often expressed in temporal logic, particularly in

CTL

and

E

A

G

LE

. No work has given a formal comparison between

E

A

G

LE

and

CTL

on semantics, though it is said that the capability of representing the “intentional” aspects of goals and the possibility of dealing with failure are the main new features of

E

A

G

LE

w.r.t.

CTL

.

According to the formal semantics for

E

A

G

LE

and

CTL

, we prove that all the

E

A

G

LE

formulas in which only

LV

1

operators (i.e. the operators representing the “intentional” aspects of goals) appear and some

E

A

G

LE

formulas including

LV

2

operators (i.e. the operators dealing with failure and qualitative preferences) can be replaced by some

CTL

formulas without any change on semantics. Finally, we also find some basic and important goals in non-deterministic domains that exceed the expressive ability of

E

A

G

LE

.