2.Syntax of CTL

A CTL formula comprises

1.  Atomic propositions such as {p, q, r…..}

2.  Path Quantifiers {A,E}

 .............a. A : all paths starting from a given state.

..............b.  E : there exists at least one path from a given state.

3.  Propositional logic operators such as AND ( ), OR ( ), NOT ( )

4.  Temporal operators {X,F,G,U}

..............a.  NE X T: next states of current state.

..............b.  F UTURE: any one of future states from the current state.

..............c.  G LOBAL: all future states from the current state.

..............d.  U NTIL: Some CTL formula holds until another CTL formula, from the current state.

X,F,G are unary operators and U is binary operator.

These temporal operators are illustrated using an example in Figure. 3.