Facts

This section outlines Fact creation and implementation. See here for more information on Facts in logic.

Fact Parameters

To create a new Fact object in PyReason, use the Fact class with the following parameters:

  1. fact_text (str): The fact in text format, where bounds can be specified or not. The bounds are optional. If not specified, the bounds are assumed to be [1,1]. The fact can also be negated using the ‘~’ symbol.

    Examples of valid fact_text are:

1. 'pred(x,y) : [0.2, 1]'
2. 'pred(x,y)'
3. '~pred(x,y)'

  1. name (str): The name of the fact. This will appear in the trace so that you know when it was applied

  2. start_time (int): The timestep at which this fact becomes active (default is 0)

  3. end_time (int): The last timestep this fact is active (default is 0)

  4. static (bool): If the fact should be active for the entire program. In which case start_time and end_time will be ignored. (default is False)

Fact Example

To add a fact in PyReason, use the command:

import pyreason as pr
 pr.add_fact(pr.Fact(fact_text='pred(x,y) : [0.2, 1]', name='fact1', start_time=0, end_time=2))