Task 1: Connect and Ask

Theory: The Client

Client starts the framex engine as a separate process and talks to it over its standard input and output. One Client is one session. What you load stays loaded until you replace it, so the calls you make build on each other.

Use it as a context manager. The with block shuts the engine down when it ends, including when your program raises:

from framex import Client

with Client() as client:
    ...

load sends a complete program and replaces whatever the session held before. It answers with the number of facts the engine now holds, counting the facts it derived for itself:

{'facts': 26}

query sends one question and returns a dictionary. A question about a fact with no variables answers {'status': 'true'}.

Task

Create main.py in your Workbench workspace and press Run program.

1. Import Client from framex.
2. Put the family program below in a module-level string called PROGRAM. It is the model from Family Tree, cut down to two rules.
3. Open a Client in a with block and load the program. Print what load returned.
4. Ask whether Elena is Dario’s grandparent, and print the answer.

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].

Only the four hasParent facts are stated. Every sibling and grandparent answer in this exercise is derived from them.

Keep this file. Every later task grows it.

Optional Extra Task

Ask a second question, this time one the program cannot support: whether Felix is Dario’s grandparent. Predict the answer before you run it.

If the engine is not on your PATH, Client() cannot start it. Point at it explicitly instead, as Installation and Quick Start shows:

client = Client(binary="/usr/local/bin/framex")