# Bx Examples Repository

# Title: undoableNotSimplyMatching

## Version: 0.1

## Type: Precise

## Overview

This example was contrived to demonstrate that being undoable does not

imply being simply matching (the two properties are incomparable: both

are implied by history ignorance)

## Models

$M = N = \{(x,\phi) | x \in {a,b,c}, \phi \in \{false, true\}\}$

## Consistency

$R((x,\phi),(y,\psi))$ iff $x = y$

## Consistency Restoration

### Forward

$\overrightarrow{R}((x,\phi),(y,\psi)) = (x,\psi)$

### Backward

$\overleftarrow{R}((x,\phi),(y,true)) = (y,\phi)$

$\overleftarrow{R}((x,\phi),(y,false)) = (y,\not\phi)$, if as sets, $\{x,y\} = \{a,c\}$

$\overleftarrow{R}((x,\phi),(y,false)) = (y,\phi)$, otherwise.

## Properties

Correct, hippocratic, undoable. **Not** simply matching, hence not history ignorant.

## Discussion

This is Example 7 from the paper cited below.

History ignorant bx are simply matching, by Prop. 4, Coro. 1 of that paper.

## References [optional section]

Perdita Stevens, *Observations relating to the equivalences induced on model sets by bidirectional transformations*, EC-EASST Vol.49, Proceedings of BX 2012. TU Berlin. ISSN 1863-2122 .bib

External link: http://journal.ub.tu-berlin.de/eceasst/article/view/714/720

## Author(s)

Perdita Stevens, James McKinna