View Source Family Tree

Mix.install([
  {:guesswork, "~> 0.7"},
  {:kino, "~> 0.13"}
])

Build a Knowledge Base

Describing family trees is often used as the 'Hello World' of logical programming, so this example will show you how to build a Knowledge Base and query it.

import Guesswork.Ast

alias Guesswork.Ast.And
alias Guesswork.Ast.Fact
alias Guesswork.Answer.Result

Start by adding rules and concrete facts to the knowledge base, in this case parent child relationships and grandparent realtionships defined as parent relationships.

defmodule KB do
  use Guesswork.KnowledgeBase.Collection

  deffact parent(:bob, :joe)
  deffact parent(:bob, :jean)
  deffact parent(:mary, :joe)
  deffact parent(:bobby, :jean)

  deffact parent(:christy, :bob)
  deffact parent(:lance, :bob)

  deffact parent(:billy, :christy)
  deffact parent(:meg, :lanceb)

  defrule grandparent(gp, gc) do 
    Fact.new(:parent, [gp, p])
    Fact.new(:parent, [p, gc])
  end
end

Query the System

Now you can query the system. This first query is simplier since it only asks questions of the concrete facts stored in the knowledge base; in this case what are bob's children.

Guesswork.query(term(Fact.new(:parent, [:bob, child])), 10, knowledge_base: KB)

You can also ask more complex questions, like what are all the grandparents of joe. You should note that the variable internal to the grandparent rule (p) is not part of the final answer set. This is because Guesswork respects lexical scoping of variables.

Guesswork.query(term(Fact.new(:grandparent, [gp, :joe])), 100, knowledge_base: KB)