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Timed CTL Model Checking in Real-Time Maude⋆ - IfI

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38 D. Lepri, E. Ábrahám, and P. Cs. Ölveczky<br />

Us<strong>in</strong>g the gcd strategy we can also determ<strong>in</strong>e a “m<strong>in</strong>imal” time <strong>in</strong>terval such<br />

that the above bounded response is satisfied <strong>in</strong> the system. In particular, we<br />

discovered that this <strong>in</strong>terval is [5, 12] by try<strong>in</strong>g different values for a and b <strong>in</strong> the<br />

<strong>in</strong>terval-bounded command<br />

Maude> (mc-tctl {<strong>in</strong>it} |=<br />

AG((’HierarchicalTrafficLight . ’Decision | (port ’Error is present))<br />

implies AF[c a, b c] (’HierarchicalTrafficLight |<br />

(’Cyel = # 1, ’Cgrn = # 0, ’Cred = # 0)))) .)<br />

Figure 8 shows the dialog w<strong>in</strong>dow for the <strong>Real</strong>-<strong>Time</strong> Maude code generation<br />

of the hierarchical traffic light model: after enter<strong>in</strong>g the error handl<strong>in</strong>g property,<br />

a simple click on the Generate button will display the result of the model<br />

check<strong>in</strong>g command execution <strong>in</strong> the “Code Generator Commands” box.<br />

7 Conclusions and Future Work<br />

We have described the semantic foundations of our T<strong>CTL</strong> model checker for<br />

<strong>Real</strong>-<strong>Time</strong> Maude. Our model<strong>in</strong>g formalism is more expressive than those of<br />

other timed model checkers, allow<strong>in</strong>g us to analyze real-time systems which<br />

are beyond the scope of other verification tools. In particular, we have proved<br />

soundness and completeness of our model checker for a class of dense-time <strong>Real</strong><br />

<strong>Time</strong> Maude specifications that conta<strong>in</strong> many systems outside the scope of other<br />

real-time model checkers. Furthermore, the <strong>in</strong>troduced T<strong>CTL</strong> model checker also<br />

provides for free a timed temporal logic model checker for <strong>in</strong>terest<strong>in</strong>g subsets of<br />

model<strong>in</strong>g languages widely used <strong>in</strong> <strong>in</strong>dustry, such as Ptolemy II and the avionics<br />

standard AADL.<br />

So far, we have only proved soundness and completeness for formulas with<br />

closed <strong>in</strong>tervals under the cont<strong>in</strong>uous semantics. We should also cover formulas<br />

with open time <strong>in</strong>tervals and the po<strong>in</strong>twise semantics. The model checker should<br />

also provide counter-examples <strong>in</strong> a user-friendly way, when possible. We should<br />

also extend our model checker to time-bounded T<strong>CTL</strong> model check<strong>in</strong>g to support<br />

the model check<strong>in</strong>g of systems with <strong>in</strong>f<strong>in</strong>ite reachable state space. F<strong>in</strong>ally, the<br />

current version of the tool is implemented at the Maude meta-level; for efficiency<br />

purposes, it should be implemented <strong>in</strong> C++ <strong>in</strong> the Maude eng<strong>in</strong>e.<br />

References<br />

1. Aalst, W.M.P.v.d.: Interval timed coloured Petri nets and their analysis. In: Application<br />

and Theory of Petri Nets 1993. LNCS, vol. 691, pp. 453–472. Spr<strong>in</strong>ger<br />

(1993)<br />

2. AlTurki, M., Meseguer, J.: <strong>Real</strong>-time rewrit<strong>in</strong>g semantics of Orc. In: Proc.<br />

PPDP’07. ACM (2007)<br />

3. Alur, R., Dill, D.L.: A theory of timed automata. Theoretical Computer Science<br />

126(2), 183–235 (1994)<br />

4. Alur, R., Henz<strong>in</strong>ger, T.: Logics and models of real time: A survey. In: <strong>Real</strong> <strong>Time</strong>:<br />

Theory <strong>in</strong> Practice. LNCS, vol. 600. Spr<strong>in</strong>ger (1992)

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