Constraint

In UML, a Constraint is a condition or restriction expressed in natural language or a machine-readable language to declare part of the Semantics of one or more Model Elements. Its evaluation yields a Boolean value and has no side effects.

SimpleModeling uses Constraints to make the valid region of a Model explicit. It distinguishes Invariants, Preconditions, Postconditions, Multiplicities, and relationship consistency rules, and separates changeable Policies from structural Constraints that must not be violated.

org.goldenport.schema.Constraint in simplemodeling-lib is an implementation boundary for validating individual values in a Value Domain. It currently handles Enum, NotEmpty, length, and numeric bounds and is evaluated after datatype normalization and before OperationRequest creation. It does not implement all Object Model Invariants, cross-Object consistency rules, Preconditions, or Postconditions.