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SYSML ELEMENTS SysML Requirements Diagram Elements Constraint blocks can only be defined on a BDD or a package diagram. A constraint block typically contains one or more constraint parameters, which are bound to properties of other blocks in a surrounding context where the constraint is used. All properties of a constraint block are constraint parameters, with the exception of constraint properties that hold the internally-nested usages of other constraint blocks. Constraints are specified only in an informal language, but a more formal language such as OCL or MathML could also be used. Sample 4.5 SysML Requirements Diagram Elements 4.5.1 Requirement Description A Requirement specifies a capability or a condition that must (or should) be satisfied. Requirements are used to establish a contract between the customer (or other stakeholders) and those responsible for designing and implementing the system. A requirement can also appear on other diagrams to show its relationship to other modeling elements. When a requirement nests other requirements, all the nested requirements apply as part of the container requirement (the requirement that contains all the nested requirements). Deleting the container requirement will thus delete all the nested requirements it contains; a functionality inherited from UML. 4.5.2 Extended Requirement Description A SysML Extended Requirement is a standard Requirement subtype, which adds some properties to a requirement element. These properties such as source, risk and verify method are important for requirement management. Specific projects should add their own properties. All these properties are now available in the standard Requirement Specification window and Requirements Table. If any of these property values is specified, a requirement is automatically converted to ExtendedRequirement. 4.5.3 Functional Requirement Description A Functional Requirement is a requirement that specifies a behavior that a system or part of a system must perform. 47 Copyright © 2009-2015 No Magic, Inc.
