SWIKB.py

# -*- coding: utf-8 -*-
from logic import KB
from pyxf import swipl


class SWIKB(KB):
    '''SWI Prolog knowledge base'''
    def __init__(self, sentence=None, path='swipl'):
        '''Constructor method
        Usage: SWIKB( sentence, path )
        sentence - Prolog sentence to be added to the KB (default: None)
        path - path to SWI Prolog executable (default: 'swipl')'''
        self.swi = swipl(path)
        if sentence:
            self.tell(sentence)

    def tell(self, sentence):
        '''Adds sentence to KB'''
        sentence = sentence.strip()
        if sentence[-1] == '.':
            sentence = sentence[:-1]
        return self.swi.query('assert(' + sentence + ')')

    def ask(self, query):
        '''Queries the KB'''
        return self.swi.query(query)

    def retract(self, sentence):
        '''Deletes sentence from KB'''
        sentence = sentence.strip()
        if sentence[-1] == '.':
            sentence = sentence[:-1]
        return self.swi.query('retract(' + sentence + ')')

    def loadModule(self, module):
        '''Loads module to KB
        Usage: instance.loadModule( path )
        path - path to module'''
        self.swi.load(module)

if __name__ == '__main__':
    kb = SWIKB()
    kb.tell('a(b,c)')
    kb.tell('a(c,d)')
    kb.tell('( p(_X,_Y) :- a(_X,_Y) )')
    kb.tell('( p(_X,_Y) :- a(_X,_Z), p(_Z,_Y) )')
    for result in kb.ask('p(X,Y)'):
        print( result )
    kb.retract('a(b,c)')