durable_rules

for real time analytics (a Ruby, Python and Node.js Rules Engine)

durable_rules is a polyglot micro-framework for real-time, consistent and scalable coordination of events. With durable_rules you can track and analyze information about things that happen (events) by combining data from multiple sources to infer more complicated circumstances.

A full forward chaining implementation (Rete) is used to evaluate facts and events in real time. A simple meta-linguistic abstraction lets you define simple and complex rulesets as well as control flow structures such as flowcharts, statecharts, nested statecharts and time driven flows.

The durable_rules core engine is implemented in C, which enables fast rule evaluation as well as muti-language support.

durable_rules can be scaled out by offloading state to a data store out of process such as Redis. State offloading is extensible, so you can integrate the data store of your choice.

In durable_rules V2, less is more: The Rete tree is fully evaluated in C. Thus, the framework is 5x to 10x faster (depending on the scenario) and does not require Redis. The programming model for posting events, asserting and retracting facts is synchronous and does not prescribe any web framework.

Getting Started

Using your scripting language of choice, simply describe the event to match (antecedent) and the action to take (consequent).

Node.js

To install the framework do: npm install durable

var d = require('durable');

d.ruleset('test', function() {
    // antecedent
    whenAll: m.subject == 'World'
    // consequent
    run: console.log('Hello ' + m.subject)
});

d.post('test', {subject: 'World'});

Python

To install the framework do: pip install durable_rules

from durable.lang import *

with ruleset('test'):
    # antecedent
    @when_all(m.subject == 'World')
    def say_hello(c):
        # consequent
        print ('Hello {0}'.format(c.m.subject))

post('test', { 'subject': 'World' })

Ruby

To install the framework do: gem install durable_rules

require "durable"

Durable.ruleset :test do
  # antecedent
  when_all (m.subject == "World") do
    # consequent
    puts "Hello #{m.subject}"
  end
end

Durable.post :test, { :subject => "World" }

Forward Inference

durable_rules super-power is the foward-chaining evaluation of rules. In other words, the repeated application of logical modus ponens to a set of facts or observed events to derive a conclusion. The example below shows a set of rules applied to a small knowledge base (set of facts).

Node.js

var d = require('durable');

d.ruleset('animal', function() {
    whenAll: {
        first = m.predicate == 'eats' && m.object == 'flies' 
        m.predicate == 'lives' && m.object == 'water' && m.subject == first.subject
    }
    run: assert({ subject: first.subject, predicate: 'is', object: 'frog' })

    whenAll: {
        first = m.predicate == 'eats' && m.object == 'flies' 
        m.predicate == 'lives' && m.object == 'land' && m.subject == first.subject
    }
    run: assert({ subject: first.subject, predicate: 'is', object: 'chameleon' })

    whenAll: m.predicate == 'eats' && m.object == 'worms' 
    run: assert({ subject: m.subject, predicate: 'is', object: 'bird' })

    whenAll: m.predicate == 'is' && m.object == 'frog'
    run: assert({ subject: m.subject, predicate: 'is', object: 'green' })

    whenAll: m.predicate == 'is' && m.object == 'chameleon'
    run: assert({ subject: m.subject, predicate: 'is', object: 'green' })

    whenAll: m.predicate == 'is' && m.object == 'bird' 
    run: assert({ subject: m.subject, predicate: 'is', object: 'black' })

    whenAll: +m.subject
    run: console.log('fact: ' + m.subject + ' ' + m.predicate + ' ' + m.object)
});

d.assert('animal', { subject: 'Kermit', predicate: 'eats', object: 'flies'});
d.assert('animal', { subject: 'Kermit', predicate: 'lives', object: 'water'});
d.assert('animal', { subject: 'Greedy', predicate: 'eats', object: 'flies'});
d.assert('animal', { subject: 'Greedy', predicate: 'lives', object: 'land'});
d.assert('animal', { subject: 'Tweety', predicate: 'eats', object: 'worms'});

Python

from durable.lang import *

with ruleset('animal'):
    @when_all(c.first << (m.predicate == 'eats') & (m.object == 'flies'),
              (m.predicate == 'lives') & (m.object == 'water') & (m.subject == c.first.subject))
    def frog(c):
        c.assert_fact({ 'subject': c.first.subject, 'predicate': 'is', 'object': 'frog' })

    @when_all(c.first << (m.predicate == 'eats') & (m.object == 'flies'),
              (m.predicate == 'lives') & (m.object == 'land') & (m.subject == c.first.subject))
    def chameleon(c):
        c.assert_fact({ 'subject': c.first.subject, 'predicate': 'is', 'object': 'chameleon' })

    @when_all((m.predicate == 'eats') & (m.object == 'worms'))
    def bird(c):
        c.assert_fact({ 'subject': c.m.subject, 'predicate': 'is', 'object': 'bird' })

    @when_all((m.predicate == 'is') & (m.object == 'frog'))
    def green(c):
        c.assert_fact({ 'subject': c.m.subject, 'predicate': 'is', 'object': 'green' })

    @when_all((m.predicate == 'is') & (m.object == 'chameleon'))
    def grey(c):
        c.assert_fact({ 'subject': c.m.subject, 'predicate': 'is', 'object': 'grey' })

    @when_all((m.predicate == 'is') & (m.object == 'bird'))
    def black(c):
        c.assert_fact({ 'subject': c.m.subject, 'predicate': 'is', 'object': 'black' })

    @when_all(+m.subject)
    def output(c):
        print('Fact: {0} {1} {2}'.format(c.m.subject, c.m.predicate, c.m.object))


assert_fact('animal', { 'subject': 'Kermit', 'predicate': 'eats', 'object': 'flies' })
assert_fact('animal', { 'subject': 'Kermit', 'predicate': 'lives', 'object': 'water' })
assert_fact('animal', { 'subject': 'Greedy', 'predicate': 'eats', 'object': 'flies' })
assert_fact('animal', { 'subject': 'Greedy', 'predicate': 'lives', 'object': 'land' })
assert_fact('animal', { 'subject': 'Tweety', 'predicate': 'eats', 'object': 'worms' })        

Ruby

require "durable"

Durable.ruleset :animal do
  when_all c.first = (m.predicate == "eats") & (m.object == "flies"),  
          (m.predicate == "lives") & (m.object == "water") & (m.subject == first.subject) do
    assert :subject => first.subject, :predicate => "is", :object => "frog"
  end

  when_all c.first = (m.predicate == "eats") & (m.object == "flies"),  
          (m.predicate == "lives") & (m.object == "land") & (m.subject == first.subject) do
    assert :subject => first.subject, :predicate => "is", :object => "chameleon"
  end

  when_all (m.predicate == "eats") & (m.object == "worms") do
    assert :subject => m.subject, :predicate => "is", :object => "bird"
  end
  
  when_all (m.predicate == "is") & (m.object == "frog") do
    assert :subject => m.subject, :predicate => "is", :object => "green"
  end
    
  when_all (m.predicate == "is") & (m.object == "chameleon") do
    assert :subject => m.subject, :predicate => "is", :object => "green"
  end

  when_all (m.predicate == "is") & (m.object == "bird") do
    assert :subject => m.subject, :predicate => "is", :object => "black"
  end
    
  when_all +m.subject do
    puts "fact: #{m.subject} #{m.predicate} #{m.object}"
  end
end

Durable.assert :animal1, { :subject => "Kermit", :predicate => "eats", :object => "flies" }
Durable.assert :animal1, { :subject => "Kermit", :predicate => "lives", :object => "water" }
Durable.assert :animal1, { :subject => "Greedy", :predicate => "eats", :object => "flies" }
Durable.assert :animal1, { :subject => "Greedy", :predicate => "lives", :object => "land" }
Durable.assert :animal1, { :subject => "Tweety", :predicate => "eats", :object => "worms" }

Pattern Matching

durable_rules provides string pattern matching. Expressions are compiled down to a DFA, guaranteeing linear execution time in the order of single digit nano seconds per character (note: backtracking expressions are not supported).

Node.js

var d = require('durable');

d.ruleset('test', function() {
    whenAll: m.subject.matches('3[47][0-9]{13}')
    run: console.log('Amex detected in ' + m.subject)
    
    whenAll: m.subject.matches('4[0-9]{12}([0-9]{3})?')
    run: console.log('Visa detected in ' + m.subject)
    
    whenAll: m.subject.matches('(5[1-5][0-9]{2}|222[1-9]|22[3-9][0-9]|2[3-6][0-9]{2}|2720)[0-9]{12}')
    run: console.log('Mastercard detected in ' + m.subject)
});

d.assert('test', { subject: '375678956789765' });
d.assert('test', { subject: '4345634566789888' });
d.assert('test', { subject: '2228345634567898' });

Python

from durable.lang import *

with ruleset('test'):
    @when_all(m.subject.matches('3[47][0-9]{13}'))
    def amex(c):
        print ('Amex detected {0}'.format(c.m.subject))

    @when_all(m.subject.matches('4[0-9]{12}([0-9]{3})?'))
    def visa(c):
        print ('Visa detected {0}'.format(c.m.subject))

    @when_all(m.subject.matches('(5[1-5][0-9]{2}|222[1-9]|22[3-9][0-9]|2[3-6][0-9]{2}|2720)[0-9]{12}'))
    def mastercard(c):
        print ('Mastercard detected {0}'.format(c.m.subject))

assert_fact('test', { 'subject': '375678956789765' })
assert_fact('test', { 'subject': '4345634566789888' })
assert_fact('test', { 'subject': '2228345634567898' })

Ruby

require "durable"
Durable.ruleset :test do
  when_all m.subject.matches('3[47][0-9]{13}') do
    puts "Amex detected in #{m.subjec