Priority: 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 speciality. Number of conditions, date of adoption, and act level decide nothing on their own: the ground is given by an explicit relation with a reason. Without the edge — Contradiction, and that is correct.
• Does not touch strict supports. Nobody defeats strict support: priority over a strict rule is a rejection LDC-E4105; a conflict of two strict rules is preserved as Contradiction forever.
• Does not assert for the defeater. A defeater only blocks: it does not support the target’s complement; after defeat — Not established, not refuted.
• Does not pick “latest/first”. Rule writing order means nothing: only the declared order wins — a strict partial order with transitive closure.
• Does not break rings at runtime. A ring of conditional priorities gives PRIORITY_CONFLICT with both sides preserved: no tie-break, “victory in a circle” is impossible.
• Does not collide same polarity. Two inferences of one relation are not opposite under any arguments; an edge between them is warning LDC-E2142, except the live chain edge of an unless chain.

Reserved and closed

• Exactly one prefer A over B edge per declaration: without prefer or on repeat — LDC-E0201 (body element order is free, but prefer uniqueness is a static check).
• reason is the named ground; the list of grounds is open per profile, but the corpus holds to five (lex_specialis, explicit_exception, lex_superior, lex_posterior, constitutional_exception).
• In a conditional priority, higher and lower are implicit meta-variables of type RuleApplication; the $higher spelling of earlier editions is rejected by the lexer. The engine publishes conflicts(higher, lower) as urn:law:std#conflicts.
• A defeater with defeat not p(x) is rejected by the parser (LDC-E0201): a defeater against a negative head is inexpressible.
• A contrary proviso on a norm head (unless C then not duty …) is undefined and rejected at lowering: a position has no complement. A bare proviso is lawful and gives a defeated position.

Neighbours and selection rule

• priority vs unless: a collision of standalone norms is an edge; a local exception of an article is a clause. See the defeasible-rules page.
• priority vs a strict negative head: a prohibition without exceptions is stronger on its own; no edge needed and forbidden (LDC-E4105).
• priority vs priority policy: a pinpoint edge between rules is an ordinary collision; a policy over the meta-domain of applications is an act hierarchy.
• lex_specialis vs lex_posterior: speciality is about norm scope, posterior about time; both only as an explicit reason, never automatic.
• Defeat of a position makes it defeated: the position is visible but publishes nothing. See the lifecycle statuses page.