Révision 225 CSL17/appendix-soundness.tex

appendix-soundness.tex (revision 225)
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\section{Proof of soundness}
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\begin{definition}
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	[Length bounded characteristic functions]
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	We define $\mubci{}$ programs $\charfn{}{A} (l , \vec u; \vec x)$, parametrised by a formula $A$ and a compatible typing $(\vec u ; \vec x)$ of its varables, as follows.
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	%	If $A$ is a $\Pi_{i}$ formula then:
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	\[
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	\begin{array}{rcl}
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	\charfn{\vec u ; \vec x}{s\leq t} (l, \vec u ; \vec x) & \dfn & \leqfn(l;s,t) \\
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	\smallskip
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	%	\charfn{}{s=t} (l, \vec u ; \vec x) & \dfn & \eq(l;s,t) \\
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	%	\smallskip
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	\charfn{\vec u ; \vec x}{\neg A} (l, \vec u ; \vec x) & \dfn & \notfn (;\charfn{\vec u ; \vec x}{A}(l , \vec u ; \vec x)) \\
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	\smallskip
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	\charfn{\vec u ; \vec x}{A\cor B} (l, \vec u ; \vec x ) & \dfn & \orfn(; \charfn{\vec u ; \vec x}{A} (l, \vec u ; \vec x , w), \charfn{\vec u ; \vec x}{B} (\vec u ;\vec x) ) \\
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	\smallskip
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	\charfn{\vec u ; \vec x}{A\cand B} (l, \vec u ; \vec x ) & \dfn & \andfn(; \charfn{\vec u ; \vec x}{A} (l, \vec u ; \vec x , w), \charfn{\vec u ; \vec x}{B} (\vec u ;\vec x) )
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	%	\end{array}
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	%	\quad
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	%	\begin{array}{rcl}
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	\\	\smallskip
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	\charfn{\vec u ; \vec x}{\exists x^\safe . A(x)} (l, \vec u ;\vec x) & \dfn & \begin{cases}
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	1 & \exists x^\safe . \charfn{}{A(x)} (l, \vec u ;\vec x , x) = 1 \\
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	0 & \text{otherwise} 
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	\end{cases} \\
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	\smallskip
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	\charfn{\vec u ; \vec x}{\forall x^\safe . A(x)} (l, \vec u ;\vec x ) & \dfn & 
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	\begin{cases}
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	0 & \exists x^\sigma. \charfn{\vec u ; \vec x}{ A(x)} (l, \vec u; \vec x , x) = 0 \\
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	1 & \text{otherwise}
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	\end{cases}
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	\end{array}
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	\]
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\end{definition}
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For the implication above, let us simply refer to the LHS as $\Wit{\vec u ; \vec x}{\Gamma} (l , \vec u ; \vec x , \vec w)$ and the RHS as $\Wit{\vec u ; \vec x}{ \Delta} (l, \vec u ; \vec x , \vec w')$, with $\vec w'$ in place of $\vec f( \cdots )$, which is a slight abuse of notation: we assume that LHS and RHS are clear from context.
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\begin{proof}

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