Lecture 15
LTL Model Checking

Stanley Bak

Remaining Due Dates

Remaining due dates are on course website

We need to choose the order for paper and final presentations

CTL Model Checking

What are each of these?

Labeling Algorithm

• First, use temporal operator equivalences to rewrite the formula in terms of only AF, EU, EX
   
• Divide final formula into subformulas based on parse tree
   
• Label all states with their atomic propositions
   
• EX \(\phi\) - Easy, label every immediate predecessor of a state with \(\phi\) in the model with EX \(\phi\)

AF \(\phi\) - Along all paths, eventually \(\phi\)

Initially, for every state with the label \(\phi\),
add the label AF \(\phi\) (why is this okay?)

E[\(\phi\) U \(\psi\)] - There exists a path where\(\phi\) holds until until \(\psi\)

Initially, for every state with a label of \(\psi\), add the label E[\(\phi\) U \(\psi\)] (why is this okay?)

Then iterate:

Efficiency

Some formulas can be handled more efficiently, for example, EG \(\psi\)