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CTL and ACTL patterns

CTL and ACTL patterns. Robert Meolic , Tatjana Kapus , Zmago Brezočnik Faculty of Electrical Engineering and Computer Science University of Maribor. CTL and ACTL patterns. Description of system. Introduction Temporal logics CTL ACTL Why patterns? Some examples Conclusion.

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CTL and ACTL patterns

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  1. CTL and ACTL patterns Robert Meolic, Tatjana Kapus, Zmago Brezočnik Faculty of Electrical Engineering and Computer Science University of Maribor

  2. CTL and ACTL patterns Description of system • Introduction • Temporal logics • CTL • ACTL • Why patterns? • Some examples • Conclusion Specification of properties AG [red!] A [{trainCross!} U {green!}] EF (EX {trainCross!} EX {carCross!})

  3. Introduction • System = states + transitions • Kripke structure: state predicates • Labelled transition system (LTS): action predicates Kripke structure LTS p a a r r b a b a p p q p a b c q r

  4. Temporal logics • Standard Boolean operators • Path quantifiers: A, E A E • Temporal operators: X, F, G, U X p This example is for CTLFor ACTL it is similar F p p p p p p G p p p q U

  5. CTL – Computation tree logic EX p AX p A state where CTL formula p is valid is p-state p p p EF p AG p E[p U q] p p p p p p p p p q p p p

  6. ACTL – Action CTL EX{a}p EF{a}p a A transition containing action predicate alphawhich is leading to the statewhere ACTL formula p is validis (alpha,p)-transition p a p • There are some abbreviations, e.g. Hennessy-Milner operators • < a > p = EX {a} p • [ a ] p = NOT EX {a} NOT p EG{a}p p a p a p a p

  7. Why patterns? • Forming CTL and ACTL formulae is a complex task • Required are theoretical background and experience • There is a danger that the formula DOES NOT express the property which an engineer intended to express • Patterns of formulae are very useful help

  8. Some examples • Always in the future, if q is valid, then p is valid all the time before it • Always in the future, if q is valid, then p is valid all the time after it • if q is valid in the future for the last time, then p is valid for at least one time before it

  9. More examples • Classification of patterns presented by M. Dwyer • ABSENCE: p is false after q • PRECEDENCE: s precedes p between q and r

  10. Conclusion • For model checking CTL and ACTL formulae are needed • Patterns enable the construction of complex formulae • The goal is automatic translation from NATURAL LANGUAGE to TEMPORAL LOGIC Our ACTL model checker EST is available at http://www.el.feri.uni-mb.si/est/ Comments and questions: meolic@uni-mb.si

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