Schemas and consistency checks

world open.
Person { label: String, father: Person }.
declare required Person label.
declare functional father.
abraham:Person[label -> "Abraham"].
isaac:Person[label -> "Isaac"; father -> abraham].
?- isaac[father -> abraham].
expect true: abraham:Person.

The schema describes value types. The required declaration demands a label for Person objects. The functional declaration limits distinct values for the father slot. These are three different checks.

Run framex validate with this filename. This example has no reported schema violations. Under the open world, the functional constraint can still be unresolved; no reported violation is not a global consistency certificate. For an experiment, work on a copy: remove Isaac’s label, use a string as his father, or add a second father value. Validate after each change.

Validation reports problems; it does not repair the data, choose a preferred father, or turn a missing label into a value. A functional declaration applies to the named property in its module, not merely to the class whose declaration happens to be nearby.

Typing is also distinct from inference declarations. A range rule can derive a class membership; a schema type constraint checks one. Neither one verifies a real-world claim.

A trustworthy knowledge base may preserve conflicting reports as separate evidence objects before deciding which assertions to accept. Do not silently overwrite disagreement to make validation pass.

Try it

Explain the difference between an absent value, a wrong type, two distinct values and an explicitly closed property. Which declaration addresses each?