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Task 3: Growing the Knowledge Base

Solution to Task 2

Show the full program and what it prints 
"""Drive a small family knowledge base from Python."""

from framex import Client

PROGRAM = """world open.

Person { hasName: String }.
Man extends Person.
Woman extends Person.

elena : Woman.
anna : Woman.
bruno : Man.
dario : Man.
felix : Man.

anna[hasParent -> elena].
bruno[hasParent -> elena].
dario[hasParent -> bruno].
felix[hasParent -> anna].

?X[hasSibling -> ?Y] <- ?X[hasParent -> ?P] AND ?Y[hasParent -> ?P] AND ?X != ?Y.
?C[hasGrandparent -> ?G] <- ?C[hasParent -> ?P] AND ?P[hasParent -> ?G].
"""


def describe(result):
    status = result["status"]
    if status == "bindings":
        rows = result["bindings"]
        return f"{len(rows)} match(es): {rows}"
    return status


def main():
    with Client() as client:
        loaded = client.load(PROGRAM)
        print("loaded:", loaded)

        result = client.query("?- dario[hasGrandparent -> elena].")
        print("grandparent:", result)

        print("ground :", describe(client.query("?- dario[hasGrandparent -> elena].")))
        print("binding:", describe(client.query("?- dario[hasGrandparent -> ?G].")))
        print("open   :", describe(client.query("?- dario[hasParent -> anna].")))
        print("many   :", describe(client.query("?- ?X[hasSibling -> ?Y].")))


if __name__ == "__main__":
    main()

Running it prints:

loaded: {'facts': 26}
grandparent: {'status': 'true'}
ground : true
binding: 1 match(es): [{'G': 'elena'}]
open   : unknown
many   : 2 match(es): [{'X': 'anna', 'Y': 'bruno'}, {'X': 'bruno', 'Y': 'anna'}]

Theory: Adding Without Reloading

There are two ways to put knowledge into a session, and they are not the same.

load replaces the session. Everything the engine held is gone, and the new program takes its place.

add extends it. The facts and rules you pass join what is already there:

client.add(source="carla : Woman.\n")

Note the keyword: add(source=...), not add(...). The same holds for retract(fact=...) later.

add answers with the change it caused:

{'added': [...], 'removed': [...]}

Both lists include derived facts, not just the ones you wrote. Adding one person who shares a parent makes the sibling rule fire, and the new sibling facts appear in added alongside the class membership the engine inferred. The engine recomputes consequences as soon as the knowledge changes; you never ask it to.

Task

Give Elena a third child.

  1. Add a module-level string NEW_FACTS stating that carla is a Woman and that Carla’s parent is elena.
  2. Call add with it, and print the added and removed lists separately.
  3. Ask who Carla’s siblings are, and print the answer with describe.

You wrote two facts. Count how many entries come back in added, and work out where each one came from.

Optional Extra Task

Add a rule rather than facts, and watch a larger cascade. Give the program an aunt rule:

?C[hasAunt -> ?A] <- ?C[hasParent -> ?P] AND ?P[hasSibling -> ?A] AND ?A : Woman.

Predict how many facts it derives before you run it. Remember that Carla is now a sibling of both Anna and Bruno.