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A Practical Introduction to PSLWeak vs. Strong Temporal Operators

A Practical Introduction to PSL: Weak vs. Strong Temporal Operators [Temporal operators can be weak or strong. A strong temporal operator such as eventually! is indicated by an exclamation point (!) as part of its name. An operator without an exclamation point, such as next, is weak. Up until now we have seen only one version of each operator, but many of the operators we have seen previously come in both weak and strong versions. The difference between weak and strong operators is important when the path is “too short” to determine whether or not everything that needs to happen to satisfy a property has indeed happened.1 For instance, consider the specification “every assertion of signal a must be followed three cycles later by an assertion of signal b”, on Trace 4.1(i). Does the specification hold or not? The assertion of signal a at cycle 2 is satisfied by the assertion of signal b at cycle 5. But what about the assertion of signal a at cycle 9? It requires an assertion of signal b at cycle 12, but the trace ends before cycle 12 is reached. Weak and strong temporal operators allow us to distinguish between the case where we would like to say that our specification holds on Trace 4.1(i), and the case where we would like to say that it does not.] http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png

A Practical Introduction to PSLWeak vs. Strong Temporal Operators

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Publisher
Springer US
Copyright
© Springer Science+Business Media, LLC 2006
ISBN
978-0-387-35313-5
Pages
27 –34
DOI
10.1007/978-0-387-36123-9_4
Publisher site
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Abstract

[Temporal operators can be weak or strong. A strong temporal operator such as eventually! is indicated by an exclamation point (!) as part of its name. An operator without an exclamation point, such as next, is weak. Up until now we have seen only one version of each operator, but many of the operators we have seen previously come in both weak and strong versions. The difference between weak and strong operators is important when the path is “too short” to determine whether or not everything that needs to happen to satisfy a property has indeed happened.1 For instance, consider the specification “every assertion of signal a must be followed three cycles later by an assertion of signal b”, on Trace 4.1(i). Does the specification hold or not? The assertion of signal a at cycle 2 is satisfied by the assertion of signal b at cycle 5. But what about the assertion of signal a at cycle 9? It requires an assertion of signal b at cycle 12, but the trace ends before cycle 12 is reached. Weak and strong temporal operators allow us to distinguish between the case where we would like to say that our specification holds on Trace 4.1(i), and the case where we would like to say that it does not.]

Published: Jan 1, 2006

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