requiredsuch

Requiredsuch is a term used in discussions of formal specification, constraint programming, and requirements engineering to denote a binding constraint that a value or object must satisfy a given predicate. The word combines "required" with the phrase "such that," echoing mathematical notation while signaling mandatory applicability in a specification context. There is no universally accepted grammar for requiredsuch, and the exact syntax may vary across proposals.

Semantically, a statement of the form requiredsuch X such that P(X) expresses that any admissible X must satisfy P. It is intended to distinguish mandatory constraints from optional predicates or permissive rules. In practice, requiredsuch is described as asserting a guard or invariant that eliminates any model or instance not meeting P.

Usage and examples are typically described in hypothetical or experimental languages. For example, in a pseudo-syntax one might encounter: requiredsuch age such that age >= 18; or requiredsuch userID such that userID is nonempty and unique. Although illustrative, these examples reflect a conceptual role rather than a standardized language feature.

Applications include requirements engineering, data validation, and formal methods where stakeholders want to mark certain conditions as non-negotiable. It is often discussed alongside concepts like invariants, preconditions, and constraints, and is sometimes positioned as a formal analogue to the intuitive notion of a non-optional rule.

Status and adoption vary; requiredsuch appears in niche discussions, speculative proposals, and some experimental languages but is not part of any widely accepted standard. See also such that, constraint, invariant, and requirements engineering for related concepts.