diff --git a/draft/draft.tex b/draft/draft.tex index 591bd2a..f6e9e5a 100644 --- a/draft/draft.tex +++ b/draft/draft.tex @@ -2150,7 +2150,7 @@ then at least $(x_1,y_3)$ is not in the behavioural equivalence, while it is in \begin{cor} Assuming that a relator $\relar$ over a functor $F\c\Set\to\Set$ satisfies $\relar(g^\op\comp f)\geq (Fg)^\op\comp Ff$ for every functions $f\c X\to Z$ and $g\c Y\to Z$, then $\hat{\relar}$-bisimilarity from a coalgebra $\alpha\c X\to FX$ to itself is sound and complete, using the axiom of choice. \end{cor} -\subsection{Egli-Milner relator} +\subsection{Egli-Milner relator and Barr relators} \begin{definition} We call the map $\emre\c\rel\to\rel$ the Egli-Milner $\powf$-relator, whenever for every relation $r\c X\rto Y$ it is defined as follows: \begin{gather*} @@ -2187,20 +2187,29 @@ Egli-Milner relator is not sound or complete, although its symmetrization is sou &\iff S\;(\powf g)^\op\comp\powf f\;T \end{align*}\qed \end{proof} -The symmetrization of the Egli-Milner relator is a Barr-relator. Barr-relator is a generalization of the Egli-Milner relator, where the functor is generalized. \begin{prop} - Assuming that $r\c X\rto Y$, and $\appr_{X}$ and $\appr_{Y}$ are posets over $FX$ and $FY$ respectively, then $\appr_{X};\hat{\emre};\appr_{Y}=\appr_{X};\hat{\emre}$ and $\appr_{X};\hat{\emre}=\hat{\emre};\appr_{Y}$. + Assuming that $r\c X\rto Y$, then $\subseteq;\hat{\emre};\subseteq=\subseteq;\hat{\emre}$ and $\subseteq;\hat{\emre}=\hat{\emre};\subseteq$. \end{prop} +Barr relator is a generalization of the Egli-Milner relator, where the functor is generalized. + \begin{definition} - A relator over a functor $F$ is a Barr-relator, shown by $\bar{F}$, iff for a relation $r\c X\rto Y$, and a span $(\pi_1\c A\to X,\pi_2\c A\to Y)$ that $r=\pi_2\comp\pi_1^\op$ we have: + A relator over a functor $F$ is a Barr relator, shown by $\bar{F}$, iff for a relation $r\c X\rto Y$, and a span $(\pi_1\c A\to X,\pi_2\c A\to Y)$ that $r=\pi_2\comp\pi_1^\op$ we have: \begin{gather*} \bar{F}r=F\pi_2\comp(F\pi_1)^\op \end{gather*} \end{definition} + \begin{prop} - Assuming that $\relar$ is a relator over $F\c\Set\to\Set$, and $\appr_{X}$ and $\appr_{Y}$ are posets over $FX$ and $FY$ respectively, then the relator that takes $r\c X\rto Y$ to $\appr_{X};\relar r;\appr_{Y}$ is a Barr-relator. + $\hat{L}$ is a Barr relator. +\end{prop} +\begin{proof} + \todo{Finish.} +\end{proof} + +\begin{prop} + Assuming that $\relar$ is a relator over $F\c\Set\to\Set$, and $\appr_{X}$ and $\appr_{Y}$ are posets over $FX$ and $FY$ respectively, then the relator that takes $r\c X\rto Y$ to $\appr_{X};\relar r;\appr_{Y}$ is a Barr relator. \end{prop} \begin{proof} \todo{Finish.}