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authorCamil Staps2018-04-19 20:03:26 +0200
committerCamil Staps2018-04-19 20:03:26 +0200
commita5177eb4a7669219d626a0d4ad533b1f86eb64a7 (patch)
treee6f533601f6b2bad75fc616ea460cca9d9dc3e29 /Assignment1/intro.tex
parentExample for satisfaction by words; still needed: satisfaction by TS (and equi... (diff)
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\erin
\subsection{Past Modalities in LTL}\label{sec:intro}
-% Explain that past Modalities are not necessary for a complete logic
-% Explain that PLTL does make the logic more succinct (Paper 1)
-%TODO: Give example on what kind of things we want to express with PLTL
As mentioned in Remark 5.16, LTL can be extended with \emph{past modalities}.
This section discusses this extension.
-The combination of LTL and Past Modalities is often called \enquote{LTL-Past} or PLTL.
-For the sake of brevity we will use the second (PLTL) to denote this combination.
+The combination of LTL and Past Modalities is often called \enquote{LTL-Past} or PLTL; we will use the second.
When temporal logic was first introduced by Arthur N. Prior in his 1957 book~\cite{Prior1957},
the logic consisted of both past and future modalities.
The complexity of the model problem does not increase with this extension~\citep{Sistla1985},
@@ -22,6 +18,5 @@ In other words, there is a class of PLTL formulae%
for which the size of all equivalent LTL formulas is $\Omega\left(2^n\right)$.
Markey achieves this proof by providing a formula that is in exactly this class.
Besides being smaller, PLTL formulas can also be easier to write and understand, as examples below will demonstrate.
-They are also included in many model checking tools, such as NuSMV.%
- \footnote{\url{http://nusmv.fbk.eu/}}
+They are also included in many model checking tools, such as NuSMV,\footnote{\url{http://nusmv.fbk.eu/}}, and as we will see in the examples they are used in practice.
For this reason, it is useful to discuss them here.