requiredhas

Requiredhas is a hypothetical predicate used in formal modeling to express that an entity possesses a specific attribute or participates in a specified relationship as a mandatory condition within a given context. It is intended to capture the idea that certain data or links must be present for validity or completeness, beyond what a simple existence relation would convey.

In formal terms, requiredhas can be treated as a binary relation between an entity x and a property or relationship p, written as requiredhas(x, p). It is typically defined together with a contextual rule that marks p as required. This distinguishes requiredhas from a plain has relation by imposing a mandatory quality on the presence of p, rather than recording observed or optional associations alone.

Examples of the concept include a data model where requiredhas(user, email) indicates that every user must have an email value, or a relational model where requiredhas(order, payment) requires a linked payment for every order. In constraint languages, requiredhas can be implemented as a rule or a constraint that enforces non-null or non-empty values, or the existence of a related record, depending on the domain.

Applications and limitations: requiredhas is discussed in the context of data validation, ontology design, and form or schema constraints. It supports expressing mandatory relationships or properties, but raises questions about scope (global vs. context-specific), interpretation of “property” versus “relationship,” and how multiplicity or optional pathways interact with the constraint. Because requiredhas is not a standard term across conventions, practitioners typically map it to existing concepts such as cardinality constraints, required fields, or SHACL-style shapes in their chosen framework.

See also: has, required, cardinality constraints, SHACL, data validation.