Skip to content

Rule sets

Rule sets are a convenient way to separate your business rules into different collections.

Doing so increases the rules' maintainability because of a better organization and fully uncoupled rules.

Tip

Rule sets are very usefull when you have a lot of rules.

Info

Most of the time, you won't need to handle different rule sets and will only use the default one: default_rule_set.

The good news is that different rule sets can be used seamlessly with the same rules engine instance 👍

Let's take the following example:

Based on that example, imagine that you need to add some rules about something totally different than the superhero school. Let's say rules for a dinosaur school.

Configuration

Update your configuration by adding a new rule set: dinosaur_school_set

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
---
rules:
  superhero_school_set:
    check_admission:
      ADMITTED_RULE:
        condition: HAS_SCHOOL_AUTHORIZED_POWER
        action: set_admission
        action_parameters:
          value: true
      DEFAULT_RULE:
        condition: null
        action: set_admission
        action_parameters:
          value: false
  dinosaur_school_set:  # 
    food_habit:
      HERBIVOROUS:
        condition: not(IS_EATING_MEAT)
        action: send_mail_to_cook
        action_parameters:
          meal: "plant"
      CARNIVOROUS:
        condition: null
        action: send_mail_to_cook
        action_parameters:
          meal: "meat"

conditions:
  HAS_SCHOOL_AUTHORIZED_POWER:
    description: "Does applicant have a school authorized power?"
    validation_function: has_authorized_super_power
    condition_parameters:
      power: input.super_power
  IS_EATING_MEAT:  # 
    description: "Is dinosaur eating meat?"
    validation_function: is_eating_meat
    condition_parameters:
      power: input.diet.regular_food

conditions_source_modules:
  - my_folder.conditions
actions_source_modules:
  - my_folder.actions

Good to know

You can define your rule sets into different YAML files (under the rules key in each).

Usage

Now that your rule sets are defined (and assuming that your condition and action functions are implemented in the right modules), you can easily use them:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
from arta import RulesEngine

input_data_1 = {
    "id": 1,
    "name": "Superman",
    "civilian_name": "Clark Kent",
    "age": None,
    "city": "Metropolis",
    "language": "french",
    "super_power": "fly",
    "favorite_meal": "Spinach",
    "secret_weakness": "Kryptonite",
    "weapons": [],
}

input_data_2 = {
    "id": 1,
    "name": "Diplodocus",
    "age": 152000000,
    "length": 31,
    "area": "north_america",
    "diet": {
        "regular_food": "plants",
    },
}

eng = RulesEngine(config_path="path/to/conf/dir")

superhero_result = eng.apply_rules(input_data_1, rule_set="superhero_school_set")  # 

dinosaur_result = eng.apply_rules(input_data_2, rule_set="dinosaur_school_set")

Good to know

Input data can be different or the same among the rule sets. It depends on the use case.

Object-Oriented Model