Rule engine in Elixir - Rete

Mix.install([
  {:neural_bridge, git: "https://github.com/lorenzosinisi/neural_bridge"}
])

Example 1: calculate the net salary of an employee in the UK

rules = [
  NeuralBridge.Rule.new(
    id: 1,
    given: """
    Person's salary is equal $salary
    """,
    then: """
    let $monthly_salary = div($salary, 12)
    Person's monthly_salary is $monthly_salary
    """
  ),
  NeuralBridge.Rule.new(
    id: 2,
    given: """
    Person's monthly_salary is equal $monthly_salary
    """,
    then: """
    let $payout = mult($monthly_salary, 0.64)
    Salary's net_amount is $payout
    """
  ),
  NeuralBridge.Rule.new(
    id: 2,
    given: """
    Salary's net_amount is equal $amount
    """,
    then: """
    Salary's net_amount is $amount
    """
  )
]

facts = """
Person's salary is 60000
Person's employment_type is "Full-time"
Person's location is "UK"
"""

NeuralBridge.Session.new("uk")
|> NeuralBridge.Session.add_rules(rules)
|> NeuralBridge.Session.add_facts(facts)
|> Map.fetch!(:inferred_facts)

Example 2: dynamic pricing

In this example, the rules calculate the discount to be applied to a customer based on the number of items they have bought in a month. The discount percentages are determined as follows:

• If the customer has bought 5 items, the discount percentage is set to 20%.
• If the customer has bought less than 2 items, the discount percentage is set to 0%.
• If the customer has bought exactly 3 items, the discount percentage is set to 10%.

rules = [
  NeuralBridge.Rule.new(
    id: 1,
    given: """
    Customer's number_of_items_bought is equal 5
    """,
    then: """
    Customer's discount_percentage is 0.2
    """
  ),
  NeuralBridge.Rule.new(
    id: 1,
    given: """
    Customer's number_of_items_bought is lesser 2
    """,
    then: """
    Customer's discount_percentage is 0.0
    """
  ),
  NeuralBridge.Rule.new(
    id: 1,
    given: """
    Customer's number_of_items_bought is equal 3
    """,
    then: """
    Customer's discount_percentage is 0.1
    """
  )
]

facts = """
Customer's number_of_items_bought is 5
"""

[
  %Retex.Wme{
    identifier: "Customer",
    attribute: "discount_percentage",
    value: 0.2
  }
] =
  NeuralBridge.Session.new("uk")
  |> NeuralBridge.Session.add_rules(rules)
  |> NeuralBridge.Session.add_facts(facts)
  |> Map.fetch!(:inferred_facts)

Example 3: loan approval

rules = [
  NeuralBridge.Rule.new(
    id: 1,
    given: """
    Applicant's credit_score is greater 700
    """,
    then: """
    Loan's approval_status is "approved"
    """
  ),
  NeuralBridge.Rule.new(
    id: 2,
    given: """
    Applicant's credit_score is lesser 500
    """,
    then: """
    Customer's at_risk is true
    Loan's approval_status is "rejected"
    """
  )
]

facts = """
Applicant's credit_score is 499
"""

[
  %Retex.Wme{
    identifier: "Customer",
    attribute: "at_risk",
    value: true
  },
  %Retex.Wme{
    identifier: "Loan",
    attribute: "approval_status",
    value: "rejected"
  }
] =
  NeuralBridge.Session.new("uk")
  |> NeuralBridge.Session.add_rules(rules)
  |> NeuralBridge.Session.add_facts(facts)
  |> Map.fetch!(:inferred_facts)

Example 3: workflow automation

rules = [
  NeuralBridge.Rule.new(
    id: 1,
    given: """
    SupportTicket's opening_time_hours greater 24
    SupportTicket's id is equal $ticke_id
    """,
    then: """
    SupportTicket's escalation_level "high"
    SupportTicket's escalated is $ticke_id
    """
  )
]

facts = """
SupportTicket's opening_time_hours is 25
SupportTicket's id is "123AB_ID"
"""

[
  %Retex.Wme{
    identifier: "SupportTicket",
    attribute: "escalation_level",
    value: "high"
  },
  %Retex.Wme{
    identifier: "SupportTicket",
    attribute: "escalated",
    value: "123AB_ID"
  }
] =
  NeuralBridge.Session.new("uk")
  |> NeuralBridge.Session.add_rules(rules)
  |> NeuralBridge.Session.add_facts(facts)
  |> Map.fetch!(:inferred_facts)