equibel 0.8.6a1

A toolkit for equivalence-based belief change

Introduction

Note: This project is still under construction. More documentation will be available soon.

Equibel is a toolkit for working with equivalence-based belief change.

It can be used in two ways:

1. Programmatically, via the equibel Python module, or

2. Interactively, via the equibeli command-line interface

Currently Supported Platforms

• OS X with Python 2.7.x

• Linux (32-bit & 64-bit) with Python 2.7.x

Installation

It is recommended that you install Equibel into a virtual environment.

1. Create a project directory and a virtual environment:

   mkdir equibel_projects
   cd equibel_projects
   virtualenv venv --python=python2.7

2. Activate the virtual environment:

   source venv/bin/activate

3. Get the source code by cloning this repository:

   git clone git://github.com/asteroidhouse/equibel.git

4. Enter the equibel directory and run pip:

   cd equibel
   pip install .

For more detailed installation steps, see the tutorial at docs/EquibelTutorial.pdf.

Quickstart

Using the Interactive CLI

You can start the interactive CLI by typing equibeli in your terminal. The

following is an example interactive session that creates a path graph on four

nodes, adds formulas to the first and last nodes, and performs a one-shot belief

sharing operation:

$ equibeli
Equibel version 0.8.5
equibel (g) > add_nodes [1,2,3,4]

    nodes: [1, 2, 3, 4]

equibel (g) > add_edges [(1,2), (2,3), (3,4)]

    edges:
        1 <-> 2
        2 <-> 3
        3 <-> 4

equibel (g) > add_formula 1 p&q&r

    node 1:
        (q & p) & r

equibel (g) > add_formula 4 ~p&~q

    node 4:
        ~p & ~q

equibel (g) > formulas

    node 1:
        (q & p) & r
    node 2:
    node 3:
    node 4:
        ~p & ~q

equibel (g) > one_shot

    One-shot belief change completed:
    ---------------------------------

    node 1:
        q & p & r
    node 2:
        r
    node 3:
        r
    node 4:
        ~p & ~q & r

Using the Python API

To use Equibel within a Python program, you need to import the equibel

module. The following is a script that does the same thing as the interactive

session – it creates a path graph, assigns formulas to nodes, find the

completion, and prints the resulting formulas at each node:

import equibel as eb

if __name__ == '__main__':
    G = eb.EquibelGraph()

    # Create nodes:
    G.add_nodes([1, 2, 3, 4])

    # Create edges:
    G.add_edges([(1,2), (1,3), (3,4), (2,4)])

    # Add formulas to nodes:
    G.add_formula(1, "p & q & r")
    G.add_formula(4, "~p & ~q")

    # Find the completion of the G-scenario:
    R = eb.completion(G)

    # Print the resulting formulas at each node:
    for node_id in R.nodes():
        print("Node {0}: {1}".format(node_id, R.formulas(node_id)))