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Decision Tree implementation for Django (pesudo code)
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| # Based on: http://springfans.com/ieeeSoftware/accChange.pdf | |
| class DecisionTable(models.Model): | |
| """Decision Table""" | |
| code = models.CharField(unique=True, max_length=8, verbose_name="Unique code for finding a decision table in code") | |
| name = models.CharField(blank=True, max_length=100, verbose_name="User friendly name for decision table") | |
| def __unicode__(self): | |
| return u"Table" | |
| class Rule(models.Model): | |
| table = models.ForeignKey(DecisionTable) | |
| code = models.CharField(unique=True, max_length=8, verbose_name="Unique code for looking up decision tables") | |
| name = models.CharField(max_length=128, verbose_name="User friendly description of decision table") | |
| priority = PositionField(collection="decision_table") | |
| def test(self, facts): | |
| for condition in self.condition.all(): | |
| if not condition.test(facts): | |
| return False | |
| return True | |
| def __unicode__(self): | |
| return u"R%d: %s" % (self.code, self.name) | |
| RESPONSE_CHOICES = ( | |
| ("Yes", True), | |
| ("No", False), | |
| ) | |
| class Condition(models.Model): | |
| """Boolean condition (e.g. condition must be true / condition must be false).""" | |
| rule = models.ForeignKey(Rule) | |
| name = models.CharField(blank=False, max_length=128, verbose_name="User friendly description of rule condition") | |
| value = models.BooleanField(required=True, default=False, choices=RESPONSE_CHOICES) | |
| def test(self, facts): | |
| return facts[self.name]==self.value | |
| def __unicode__(self): | |
| return u"C%d: %s" % (self.code, self.name) | |
| class Action(models.Model): | |
| """Data returned by rule""" | |
| rule = models.ForeignKey(Rule) | |
| code = models.CharField(unique=True, max_length=8, verbose_name="Unique code for identifying actions in code.") | |
| name = models.CharField(blank=False, max_length=128, verbose_name="User friendly description of rule action") | |
| order = PositionField("rule") | |
| def __unicode__(self): | |
| return u"A%d: %s" % (self.code, self.name) |
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