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diff --git a/Assignment1/intro.tex b/Assignment1/intro.tex index 0d359f3..6df3700 100644 --- a/Assignment1/intro.tex +++ b/Assignment1/intro.tex @@ -9,8 +9,9 @@ The combination of LTL and Past Modalities is often called \enquote{LTL-Past} or For the sake of brevity we will use the second (PLTL) to denote this combination. 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. -Only later, when it was shown that past modalities do not increase the expressive power of LTL~\cite{Gabbay1980}, -computing scientists stopped considering past modalities for reasons of minimality. +The complexity of the model problem does not increase with this extension~\citep{Sistla1985}, + but neither does the expressiveness of the system compared to LTL~\citep{Gabbay1980}. +Eventually, formal computing scientists stopped using past modalities for reasons of minimality. \erin In 2003, Nicolas Markey showed that while past modalities do not increase expressive power, |