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Spencer Killen 2024-11-27 17:41:29 -07:00
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\BOOKMARK [1][-]{section.1}{\376\377\000P\000r\000e\000l\000i\000m\000i\000n\000a\000r\000i\000e\000s}{}% 1
\BOOKMARK [1][-]{section.2}{\376\377\000L\000a\000t\000t\000i\000c\000e\000\040\000T\000h\000e\000o\000r\000y}{}% 2
\BOOKMARK [1][-]{section.3}{\376\377\000D\000e\000t\000e\000r\000n\000m\000i\000n\000i\000s\000t\000i\000c\000\040\000A\000F\000T}{}% 3

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\documentclass{article}
\usepackage{natbib}
\usepackage{xspace}
\usepackage{xparse}
\usepackage{environ}
\usepackage{hyperref}
\usepackage{bm}
\usepackage[english]{babel}
@ -37,29 +40,15 @@ pdfpagemode=FullScreen,
\maketitle
\begin{definition}
\AnNdaoO is a $\langle \lte, \lte \rangle$-\Monotone function $o: \LL^2 \rightarrow \powersetO(\LL^2)$ s.t.\ for any $x \in \LL^2$
\begin{itemize}
\item $o(x, x)_1 = o(x, x)_2$
\end{itemize}
\end{definition}
\section{Preliminaries}
\input{sections/preliminaries.tex}
\begin{definition}
\AnNdaoO is {\em extra consistent} if for every $\lte$-\Prefixpoint $y$ of $o(x, \cdot)_2$, $x \lte y$.
\end{definition}
What about the bottom half does it matter?
\begin{lemma}[From Heyninck]
\AnNdaoO is consistent, for every $(x, y)$, $o(x, y)_1 \times o(x, y)_2$ contains at least one consistent pair.
\end{lemma}
\begin{definition}
Regular stable revision
\begin{align*}
S(o)(x, y)_1 \define \minLattice_{\lte}(\fixpointsOf(o(\cdot, y))) \\
S(o)(x, y)_2 \define \minLattice_{\lte}(\fixpointsOf(o(x, \cdot)))
\end{align*}
\end{definition}
\begin{definition}
"beta" stable revision

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\section{Lattice Theory}
\definitionBody{powerset}{Given a set $S$, we denote its powerset, i.e.\ $\{ x \subseteq S \}$ with $\powerset(S)$. We use $\powersetO(S)$ to denote the powerset of $S$ without the empty set.}
\definitionBody{poset}{
We call $\langle S, \lte \rangle$ a {\em poset} (a partially ordered set) if $\lte$ is reflexive, transitive and antisymmetric.
}
\definitionBody{lubglb}{An element is an {\em upper or lower bound} of a subset $S$ of a \Poset if it is greater than or equal or less than or equal, respectively, to every element inside $S$.}
\definitionBody{completelattice}{A {\em complete lattice} is a \Poset $\langle \LL, \lte \rangle$ s.t.\ every subset $S$ of $\LL$ has a unique greatest lower bound $\glb^{\LL} S$ and least upper bound $\lub^{\LL} S$}
\definitionBody{topbot}{We use $\top^{\LL}$ and $\bot^{\LL}$ to denote $\lub^{\LL} \LL$ and $\glb^{\LL} \LL$ respectively.}
\definitionBody{monotone}{A function $f: A \rightarrow B$ is {\em monotone} w.r.t. the orderings $\langle A, \lteSub{A} \rangle$ and $\langle B, \lteSub{B} \rangle$ if for all $a_1, a_2 \in A$, $a_1 \lte a_2$ implies $f(a_1) \lte f(a_2)$}
\definitionBody{image}{Given a function $f: A \rightarrow B$, we use $f[A]$ to denote the {\em image of $f$} w.r.t.\ $A$, i.e.\ the set $\{ f(a) ~|~ a \in A \} \subseteq B$.
With abuse to notation, when given a set of functions $F$, we write $\bigcup \{ f\image{A} ~|~ f \in F \}$ as $F\image{A}$.}
\section{Deternministic AFT}
The original definition of approximators from Denecker et al.\ \cite{denecker2000approximations}, which has been relaxed following Heyninck et al.\ \cite{nondet2}.
% \begin{definition}
% \definitionBody{deterministicapproximator}{
% A {\em deterministic approximator} $o: \LL \rightarrow \LL$ is an \Exact \Monotone function over a \CompleteLattice $\langle \LL, \lte \rangle$
% }
% \end{definition}
\begin{definitionOf}{deterministicapproximator}
A {\em deterministic approximator} $o: \LL \rightarrow \LL$ is an \Exact \Monotone function over a \CompleteLattice $\langle \LL, \lte \rangle$
\end{definitionOf}
\begin{definitionOf}{deterministicstablerevisionoperator}
Given \AnApproximator $o: \LL \rightarrow \LL$, its {\em stable revision operator $S(o): \LL^2 \rightarrow \LL^2$} as follows:
\begin{align*}
S(o)(x, y) \define (\lfp~o(\partialApp, y), \lfp~(x, \partialApp))
\end{align*}
\end{definitionOf}
In later work, Denecker et al.~\cite{DeneckerMT04} establish an alternative theory of AFT based around operators that are restricted to the smaller domain, $\LL^c = \{ (x, y) \in \LL^2 ~|~ x \lte y \}$.
The set $\L^c$ only contains the pairs that are \ConsistentPair.
\definitionBody{consistentpair}{A pair $(x, y)$ is {\em consistent} if $x \lte y$.}
\begin{definitionOf}{deterministicbetaapproximator}
A {\em $\beta$-approximator} $o \LL^c \rightarrow \LL^c$ is \AnApproximator restricted and closed under $\LL^c$
\end{definitionOf}
% Critically, stable revision is defined differently for \BetaApproximators
In the same work, Denecker et al.~\cite{DeneckerMT04} use a slightly different notion of stable revision.
Because, for a \BetaApproximator $o$, the function for any $(x, y) \in \LL^c$
\begin{align*}
o(\partialApp, y)_1:& \latticeinterval{\bot}{y} \rightarrow \latticeinterval{\bot}{y} \\
o(x, \partialApp)_2:& \latticeinterval{x}{\top} \rightarrow \latticeinterval{x}{\top}
\end{align*}
So naturally, \Definition{deterministicstablerevisionoperator} applied to \BetaApproximators also uses this limited range.
For our purposes, we adapt their definition to fit \Approximators and \BetaApproximators.
\begin{definitionOf}{deterministicbetastablerevisionoperator}
Given \AnApproximator $o: \LL^2 \rightarrow \LL^2$
\begin{align*}
\Sdetbeta(o)(x, y)_1 \define \minLattice_{\lte} \big( \fixpointsOf(o(\partialApp, y)_1) \setminus ((x \upclosure) \setminus (y \downclosure)) \big)
\\
\Sdetbeta(o)(x, y)_2 \define \minLattice_{\lte} \big( \fixpointsOf(o(x, \partialApp)_2) \setminus ((y \downclosure) \setminus (x \upclosure)) \big)
\end{align*}
\end{definitionOf}
The symmetric version
\begin{definitionOf}{deterministicbetastablerevisionoperator}
Given \AnApproximator $o: \LL^2 \rightarrow \LL^2$
\begin{align*}
\Sdetbeta(o)(x, y)_1 &\define \minLattice_{\lte} \Bigg( \fixpointsOf(o(\partialApp, y)_1) \setminus \bigg(
\Big( ((x \glbBinary y) \upclosure) \union ((x \lubBinary y) \downclosure) \Big)
\setminus
\Big( ((x \glbBinary y) \upclosure) \intersect ((x \lubBinary y) \downclosure) \Big)
\bigg) \Bigg)
\\
\Sdetbeta(o)(x, y)_2 &\define \Sdetbeta(o)(y, x)_1
\end{align*}
\end{definitionOf}
\begin{propositionOf}{deterministicstablerevisionoperatorsymmetry}
Given an \Approximator $o: \LL^2 \rightarrow \LL^2$ that is \Symmetric, its \BetaStableRevisionOperator $S(o)$ is also \Symmetric.
Under symmetry the two are equivalent for consistent partition
\end{propositionOf}
\begin{proof}
By \Symmetry, we have $\fixpointsOf(o(\partialApp, y)_1) = \fixpointsOf(o(x, \partialApp)_2)$
\end{proof}
\Proposition{deterministicstablerevisionoperatorsymmetry}
\begin{definition}
\AnNdaoO is a $\langle \lte, \lte \rangle$-\Monotone function $o: \LL^2 \rightarrow \powersetO(\LL^2)$ s.t.\ for any $x \in \LL^2$
\begin{itemize}
\item $o(x, x)_1 = o(x, x)_2$
\end{itemize}
\end{definition}
What about the bottom half does it matter?
\begin{lemma}[From Heyninck]
\AnNdaoO is consistent, for every $(x, y)$, $o(x, y)_1 \times o(x, y)_2$ contains at least one consistent pair.
\end{lemma}
\begin{definition}
Regular stable revision
\begin{align*}
S(o)(x, y)_1 \define \minLattice_{\lte}(\fixpointsOf(o(\cdot, y))) \\
S(o)(x, y)_2 \define \minLattice_{\lte}(\fixpointsOf(o(x, \cdot)))
\end{align*}
\end{definition}

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\newcommand{\definitionBody}[2]{\hypertarget{glossary:#1}{#2}}
\newcommand{\definitionLink}[2]{\hyperlink{glossary:#1}{#2}\xspace}
\newcommand{\Definition}[1]{\definitionLink{#1}{Definition~\ref{definition:#1}}}
\NewEnviron{definitionOf}[1]{
\begin{definition}\label{definition:#1}
\definitionBody{#1}{\BODY}
\end{definition}
}
\NewEnviron{propositionOf}[1]{
\begin{proposition}\label{proposition:#1}
\BODY
\end{proposition}
}
\newcommand{\Proposition}[1]{\hyperref[proposition:#1]{Proposition~\ref{proposition:#1}}}
\newcommand{\LeastFixpoint}{\definitionLink{leastfixpoint}{least fixpoint}}
\newcommand{\ConsistentPair}{\definitionLink{consistentpair}{consistent}}
\newcommand{\Monotone}{\definitionLink{monotone}{monotone}}
\newcommand{\Exact}{\definitionLink{deterministicexactapproximator}{exact}}
\newcommand{\Symmetric}{\definitionLink{deterministicsymmetricapproximator}{symmetric}}
\newcommand{\Symmetry}{\definitionLink{deterministicsymmetricapproximator}{symmetry}}
\newcommand{\BetaApproximator}{\definitionLink{deterministicbetaapproximator}{$\beta$-approximator}}
\newcommand{\BetaStableRevisionOperator}{\definitionLink{deterministicbetastablerevisionoperator}{$\beta$-stable revision operator}}
\newcommand{\BetaApproximators}{\definitionLink{deterministicbetaapproximator}{$\beta$-approximators}}
\newcommand{\Approximator}{\definitionLink{deterministicapproximator}{approximator}}
\newcommand{\Approximators}{\definitionLink{deterministicapproximator}{approximators}}
\newcommand{\AnApproximator}{\definitionLink{deterministicapproximator}{an approximator}}
\let\SdetNoLink\Sdet
\renewcommand{\Sdet}{\definitionLink{deterministicstablerevisionoperator}{\SdetNoLink}}
\let\SdetbetaNoLink\Sdetbeta
\renewcommand{\Sdetbeta}{\definitionLink{deterministicbetastablerevisionoperator}{\SdetbetaNoLink}}
\newcommand{\Image}{\definitionLink{image}{monotone}}
\let\imageNoLink\image{}
\renewcommand{\image}[1]{\imageNoLink{#1}}

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\newcommand{\image}[1]{[#1]}
\newcommand{\define}{\coloneqq}
\newcommand{\union}{\cup}
\newcommand{\intersect}{\cap}
\newcommand{\glb}{\bigwedge}
\newcommand{\lub}{\bigvee}
\newcommand{\glbBinary}{\land}
\newcommand{\lubBinary}{\lor}
\newcommand{\powerset}{\wp}
\newcommand{\powersetO}{\wp^o}
\newcommand{\upclosure}{\uparrow}
\newcommand{\downclosure}{\downarrow}
\newcommand{\partialApp}{\cdot}
\newcommand{\lfp}{\textbf{lfp}}
\newcommand{\latticeinterval}[2]{[#1, #2]}
\newcommand{\Sdet}{S}
\newcommand{\Sdetbeta}{S^{\beta}}

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\definition{powerset}{Given a set $S$, we denote its powerset, i.e.\ $\{ x \subseteq S \}$ with $\powerset(S)$. We use $\powersetO(S)$ to denote the powerset of $S$ without the empty set.}
\definition{poset}{
\definitionBody{powerset}{Given a set $S$, we denote its powerset, i.e.\ $\{ x \subseteq S \}$ with $\powerset(S)$. We use $\powersetO(S)$ to denote the powerset of $S$ without the empty set.}
\definitionBody{poset}{
We call $\langle S, \lte \rangle$ a {\em poset} (a partially ordered set) if $\lte$ is reflexive, transitive and antisymmetric.
}
\definition{lubglb}{An element is an {\em upper or lower bound} of a subset $S$ of a \Poset if it is greater than or equal or less than or equal, respectively, to every element inside $S$.}
\definition{completelattice}{A {\em complete lattice} is a \Poset $\langle \LL, \lte \rangle$ s.t.\ every subset $S$ of $\LL$ has a unique greatest lower bound $\glb^{\LL} S$ and least upper bound $\lub^{\LL} S$}
\definition{topbot}{We use $\top^{\LL}$ and $\bot^{\LL}$ to denote $\lub^{\LL} \LL$ and $\glb^{\LL} \LL$ respectively.}
\definition{monotone}{A function $f: A \rightarrow B$ is {\em monotone} w.r.t. the orderings $\langle A, \lteSub{A} \rangle$ and $\langle B, \lteSub{B} \rangle$ if for all $a_1, a_2 \in A$, $a_1 \lte a_2$ implies $f(a_1) \lte f(a_2)$}
\definition{image}{Given a function $f: A \rightarrow B$, we use $f[A]$ to denote the {\em image of $f$} w.r.t.\ $A$, i.e.\ the set $\{ f(a) ~|~ a \in A \} \subseteq B$.
\definitionBody{lubglb}{An element is an {\em upper or lower bound} of a subset $S$ of a \Poset if it is greater than or equal or less than or equal, respectively, to every element inside $S$.}
\definitionBody{completelattice}{A {\em complete lattice} is a \Poset $\langle \LL, \lte \rangle$ s.t.\ every subset $S$ of $\LL$ has a unique greatest lower bound $\glb^{\LL} S$ and least upper bound $\lub^{\LL} S$}
\definitionBody{topbot}{We use $\top^{\LL}$ and $\bot^{\LL}$ to denote $\lub^{\LL} \LL$ and $\glb^{\LL} \LL$ respectively.}
\definitionBody{monotone}{A function $f: A \rightarrow B$ is {\em monotone} w.r.t. the orderings $\langle A, \lteSub{A} \rangle$ and $\langle B, \lteSub{B} \rangle$ if for all $a_1, a_2 \in A$, $a_1 \lte a_2$ implies $f(a_1) \lte f(a_2)$}
\definitionBody{image}{Given a function $f: A \rightarrow B$, we use $f[A]$ to denote the {\em image of $f$} w.r.t.\ $A$, i.e.\ the set $\{ f(a) ~|~ a \in A \} \subseteq B$.
With abuse to notation, when given a set of functions $F$, we write $\bigcup \{ f\image{A} ~|~ f \in F \}$ as $F\image{A}$.}