Negation and truth statuses: boundaries

What the construct does NOT do in 0.2: limits, closed lists, neighbouring constructs, and the selection rule.

OverviewBoundariesCorpus formsPitfalls

Does not do

• Does not infer absence from silence. Absence of positive support is Not established, not refuted, not Refuted. Negation-as-failure exists in 0.2 in no form: neither an unfired rule nor not_known gives negative support.
• Does not refute through not_known. not_known(P) is true on absent support and infers nothing about P: the answer on P itself stays Not established, not refuted.
• Does not read a conflict by sides. An atom in Contradiction activates neither p(x) nor not p(x); one side is taken only through supported(P).
• Does not apply De Morgan. not is only over an atom; double negation is not eliminated, there is no excluded middle.
• Does not close the world without a holder. A closure is local (a domain of the same arity), dated (complete_as_of is a moment), and optionally windowed (by effective); outside the domain — Not established, not refuted.

Reserved and closed

• opposed, conflicted, no_evidence are 0.2 hard keywords: the lexer rejects them as terms, LDC-E0201. The Contradiction branch is not read by a separate test in 0.2.
• not_known is only in a rule body; in a head — LDC-E1302 (warning: the node is skipped, there is no rule in the compiled output).
• Underscore _ is only a positive body literal; in a head, under not, in a status test, and in a case fact — LDC-E0207.

Neighbours and selection rule

• not p vs not_known(P): established absence with a source vs the “as yet unknown” stage. No source — no not.
• not_known(P) vs closure: reading ignorance without a certificate vs a completeness claim with a closure certificate.
• Body not p vs refuted(p): the same Refuted reading, but the test does not bind variables — a positive conjunct is needed nearby.
• Negation vs unless/priority: not gives negative support and stays silent on Contradiction; a refusal’s victory over a fact is by priority between defeasible rules, not by negation strength (see the pitfalls, item 8).