Chapter 16. Functions, Constraints and Requirements

Functions, which are called “calculation definitions”, can be defined with calc def and then used in expressions, e.g., for binding a derived attribute to a computed value.

Constraints can be declared in the form of constraint properties and either defined by an inline condition or typed by a constraint definition. A constraint can be defined without being asserted, in which case it can be checked, but its violation does not create a compliance issue.

A requirement can be defined in the form of a reusable template, called requirement definition, specifying a stakeholder-imposed constraint on a design element called subject. A design solution must satisfy the constraint to be a valid solution. Requirements may be specified informally using text statements (commonly known as "shall" statements) or formally using constraint expressions.

A verification case has as its objective the verification of one or more requirements on a subject — meaning the requirements are asserted to be true if the subject passes whatever sort of testing is being modeled.