Requirements can be captured in SysML Requirement Diagrams.
A composition links a high-level requirements “r” to requirements that are supposed to compose “r”.
A refine relation expresses a requirement which gives more details (e.g., more concrete values, or more concrete model elements) to a requirement.
A DereiveReqt relation builds a requirement from other requirements (i.e. it is derived from other requirements). This relation is particularly used when a requirement expresses required techincal aspects from non technical requirements.
Security requirements in TTool can be made explicit, with e.g. “confidentiality”, “integrity”, etc. The following definitions make these terms more explicit.
Privacy is guaranteed if the relation between an entity and a set of information is confidential.
An example: In a social network, for non administrator users, the user of a message shall not be linkable to that message but two messages sent by the same user shall be linkable to each other.
Confidentiality is satisfied when authorized entities are the only ones that can know a given quantum of information.
Examples: - The content of Messages sent from A to B shall be known only by A and B - The state of a state machine shall be known only by its execution engine