A small family knowledge graph

world open.
abraham:Man.
sarah:Woman.
isaac:Man[father -> abraham; mother -> sarah].
jacob:Man[father -> isaac; mother -> rebekah].
esau:Man[father -> isaac; mother -> rebekah].
rebekah:Woman.
?Parent[son -> ?Child] <- ?Child:Man AND (
    ?Child[father -> ?Parent] OR ?Child[mother -> ?Parent]
).
?- ?Mother:Woman AND ?Mother[son -> ?Son]
   AND ?Son[father -> abraham].
expect true: sarah[son -> isaac].

A frame bundles named properties of one object. Isaac’s frame records two relationships, to Abraham and Sarah. A semicolon separates properties; it does not mean sequence or choice.

The rule reads: a parent’s son is a male child whose father or mother is that parent. OR is inclusive. The query joins the mother, son and father by reusing variables. Its answer is Mother = sarah, Son = isaac. Binding labels in displayed output may omit the question-mark marker used in source.

The final expect is an executable assertion about the answer. It is not evidence that makes that answer true. Use framex test with the same filename to check expectations explicitly; changing expect true to another expected truth value should make a mismatching test fail.

Try it

Add a second male child with the same parents. Predict how many query rows appear and explain the shared bindings.