Claims

A claim is a statement: a subject (an entity), a predicate, an object (an entity, a value, or nothing), optional qualifiers, a polarity (true, or false for “not”) and optionally the record it is about.

Predicates are declared per project: whether their object is an entity, a value or nothing, and their cardinality. A predicate of cardinality one is functional: a subject has one value for it at a time (where someone lives), so two different values in the same slot are a contradiction. Predicates beginning with umwelt: are reserved and have built-in meaning, such as umwelt:member-of (group membership), umwelt:name and umwelt:alias (names over time) and umwelt:holds (what one holder thinks another knows).

Every claim has a claim key, a stable hash of what it says that ignores polarity, so “Bob is in the castle” and “Bob is not in the castle” share a key. Functional claims also have a slot key (subject and predicate). See claim-key.md.