diff --git a/draft/draft.tex b/draft/draft.tex index 3e200c5..c13055f 100644 --- a/draft/draft.tex +++ b/draft/draft.tex @@ -2209,7 +2209,8 @@ Barr relator is a generalization of the Egli-Milner relator, where the functor i \end{proof} \begin{definition}[One-sided Barr relator] - A relator over a functor $F$ is a one-sided Barr relator, shown by $\overrightarrow{F}$, iff for a partial order $\appr$ over $F$, 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: + Given a relation $r$, and take a span $(\pi_1\c A\to X,\pi_2\c A\to Y)$ that $r=\pi_2\comp\pi_1^\op$. Assuming that $\sqsubseteq$ is a partial order over a functor $F$, then the relator over $F$ and shown with $\overrightarrow{F}$ is a \emph{one-sided Barr relator} iff we have: +% A relator over a functor $F$ is a one-sided Barr relator, shown by $\overrightarrow{F}$, iff for a partial order $\appr$ over $F$, 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*} \overrightarrow{F}r=F\pi_2\comp\sappr\comp(F\pi_1)^\op \end{gather*} @@ -2241,20 +2242,67 @@ Barr relator is a generalization of the Egli-Milner relator, where the functor i So we have $\hat{\overrightarrow{F}}\leq \bar{F}$. Now, we are left to show that $\bar{F}\leq\hat{\overrightarrow{F}}$. For that, reading the given proof from the end to the starting point is sufficient. \end{proof} + +\begin{lemma} + Then the following propositions hold: + \begin{enumerate} + \item $\powf\pi_2\comp\supseteq\comp(\powf\pi_1)^\op\quad=\quad\supseteq\comp \powf\pi_2\comp(\powf\pi_1)^\op$ + \item $\powf\pi_1\comp\supseteq\comp(\powf\pi_2)^\op\quad=\quad\supseteq\comp \powf\pi_1\comp(\powf\pi_2)^\op$ + \end{enumerate} +\end{lemma} +\begin{proof} + Without loss of generality, we assume $i,j\in\{1,2\}$, and $i\neq j$, and prove $\powf\pi_j\comp\supseteq\comp(\powf\pi_i)^\op\quad=\quad\supseteq\comp \powf\pi_j\comp(\powf\pi_i)^\op$. + Assuming $x \mathrel{\powf\pi_j\comp\supseteq\comp(\powf\pi_i)^\op} y$, then exist $z$ and $z'$ such that + \begin{gather*} + z \mathrel{(\powf\pi_i)} x,\\ + z \mathrel{\subseteq} z',\\ + z'\mathrel{(\powf\pi_j)} y. + \end{gather*} + Then from $z \mathrel{\subseteq} z'$ we get $\powf\pi_j(z)\mathrel{\subseteq}y$. So, we have $z\mathrel{\supseteq\comp \powf\pi_j} y$, thus $x\mathrel{\supseteq\comp \powf\pi_j\comp(\powf\pi_i)^\op} y$. + + Now, assuming $x \mathrel{\supseteq\comp \powf\pi_j\comp(\powf\pi_i)^\op} y$, then there exist $z$ and $y'$ such that + \begin{gather*} + z\mathrel{(\powf\pi_i)} x,\\ + z \mathrel{(\powf\pi_j)} y',\\ + y' \mathrel{\subseteq} y. + \end{gather*} + We take the set $w=z\cup \powf\pi_i(z)\times y$ for which we have $z\subseteq w$ and $\powf\pi_j(w)=y$. So, we have $w \mathrel{(\powf\pi_j)} y$, $z\mathrel{\subseteq} w$, and $z\mathrel{(\powf\pi_i)} x$ that gives $x \mathrel{\powf\pi_j\comp\supseteq\comp(\powf\pi_i)^\op} y$.\qed +\end{proof} + +%\begin{lemma} +% Assuming that $F\pi_1$ and $F\pi_2$ are monotone with respect to $\sqsubseteq$ that is an order over $F$, then the following propositions hold: +% \begin{enumerate} +% \item $F\pi_2\comp\sqsupseteq\comp(F\pi_1)^\op\quad=\quad\sqsupseteq\comp F\pi_2\comp(F\pi_1)^\op$ +% \item $F\pi_1\comp\sqsupseteq\comp(F\pi_2)^\op\quad=\quad\sqsupseteq\comp F\pi_1\comp(F\pi_2)^\op$ +% \end{enumerate} +%\end{lemma} +%\begin{proof} +% Without loss of generality, we assume $i,j\in\{1,2\}$, and $i\neq j$, and prove $F\pi_j\comp\sqsupseteq\comp(F\pi_i)^\op\quad=\quad\sqsupseteq\comp F\pi_j\comp(F\pi_i)^\op$. +% +% Assuming $x \mathrel{F\pi_j\comp\sqsupseteq\comp(F\pi_i)^\op} y$, then exist $z$ and $z'$ such that +% \begin{gather*} +% z \mathrel{(F\pi_i)} x,\\ +% z \mathrel{\sqsubseteq} z',\\ +% z'\mathrel{(F\pi_j)} y. +% \end{gather*} +% Then from $z \mathrel{\sqsubseteq} z'$ we get $F\pi_j(z)\mathrel{\sqsubseteq}y$. So, we have $z\mathrel{\sqsupseteq\comp F\pi_j} y$, thus $x\mathrel{\sqsupseteq\comp F\pi_j\comp(F\pi_i)^\op} y$. +% +% Now, assuming $x \mathrel{\sqsupseteq\comp F\pi_j\comp(F\pi_i)^\op} y$, then there exist $z$ and $y'$ such that +% \begin{gather*} +% z\mathrel{(F\pi_i)} x,\\ +% z \mathrel{(F\pi_j)} y',\\ +% y' \mathrel{\sqsubseteq} y. +% \end{gather*} +%\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.} \end{proof} -\begin{prop} - The following propositions hold: - \begin{itemize} - \item $\powf\pi_2\comp\supseteq\comp(\powf\pi_1)^\op\quad=\quad\supseteq\comp\powf\pi_2\comp(\powf\pi_1)^\op$ - \item $\powf\pi_1\comp\supseteq\comp(\powf\pi_2)^\op\quad=\quad\supseteq\comp\powf\pi_1\comp(\powf\pi_2)^\op$ - \end{itemize} -\end{prop} + \end{document}