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→Finite State Model
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''This is a draft document.'' | ''This is a draft document.'' | ||
We use an extended finite state model called '''Statecharts''' to specify the operation of the NSS cryptographic module. [http://www.wisdom.weizmann.ac.il/~harel/SCANNED.PAPERS/Statecharts.pdf Statecharts] were invented by David Harel to solve the state explosion problem of complex systems. Statecharts extend the finite state model with two concepts: | |||
We use an extended finite state model called '''Statecharts''' to specify the NSS cryptographic module. [http://www.wisdom.weizmann.ac.il/~harel/SCANNED.PAPERS/Statecharts.pdf Statecharts] were invented by David Harel to solve the state explosion problem of complex systems. Statecharts extend the finite state model with two concepts: | * '''Hierarchical substates''' represent a refinement of a state, exposing more details. In addition to allowing us to specify a system's behavior at multiple levels of details, hierarchical substates can also reduce the number of transitions. A single transition leaving a composite state is equivalent to multiple transitions each leaving a hierarchical substate of the composite state. For example, transition 4.0 in our state transition diagram is such a transition. | ||
* '''Hierarchical substates''' represent a refinement of a state, exposing more details. | |||
* '''Concurrent substates''' represent concurrent subsystems that operate in parallel. | * '''Concurrent substates''' represent concurrent subsystems that operate in parallel. | ||
Statecharts have been adopted by the [http://www.uml.org/ Unified Modeling Language (UML)]. | Statecharts have been adopted by the [http://www.uml.org/ Unified Modeling Language (UML)]. | ||
==Finite State Model== | |||
The state transition diagram of the NSS cryptographic module is shown below as a UML Statechart. | The state transition diagram of the NSS cryptographic module is shown below as a UML Statechart. | ||