Module value 

QISP typed value model — the typed function descriptor, execution/exactness classification, and the stable QISP error codes.

This module is the typed signature foundation for the Immersive SPARQL (QISP) profile (plan §4.2 “No untyped u64 -> u64 public function contract”, §4.3 “Error semantics”, §4.4 “exactness profiles”). Every type here is a fixed-size, #[repr(C)], Copy record with no String/Box/Vec inside — it belongs on the zero-heap evaluation tier, matching the house idiom in sparql_ast.rs.

Provisional, Editor’s-Draft IRIs (no compatibility promise) — see the namespace constants in the parent mod.

Structs

ImmersiveFunctionDescriptor

Typed function descriptor for a QISP extension function (plan §4.2, verbatim field set plus the ExactnessClass referenced there).

Enums

ExactnessClass

Exactness profile (plan §4.4). Exactness is an explicit contract, never an invisible server preference.

ExecutionClass

How a function is allowed to execute (plan §4.2 / §6.1).

ImmersiveValueKind

The closed set of typed value kinds a QISP function may consume or produce.

QispError

Stable QISP error codes (plan §4.3). SPARQL expression errors stay expression errors — they MUST NOT silently become false. Each variant has a stable kebab-case code() for machine-readable diagnostics and Problem-Details type IRIs.