Next state logic

The next state logic and the output logic are purely combinational while the present state consists of sequential memoiy elements (flip-flops). Each active clock transition causes a change of state from the present state to the next state. 

Sequence logic is often, but not necessarily, coupled with the concept of a process state. Basically, the sequence logic determines when the process should proceed from the current state to the next, and sometimes what the next state should be. 

In our polymodal logic, there are two independent dimensions time and state. For each of the five PTL temporal operators, there is one operator for time and one for state, and the two are distinguished by an overscore for the state operator (e.g. o for next time and o for next state). Propositions take on values that may be different for each < time, state > pmr. 

The data path modules are specified abstractly. For instance, an arithmetic-logic unit (ALU) would have its width and functions (e.g. add, subtract, and OR) specified. As illustrated in Figure 1-1, the controller is described textually as an abstract state machine (states, next states, and data path elements to enable). The controller is not any more detailed since the actual implementations of the data path... 

Monitor properties are expressed in CTL (Computation Tree Logic), which is entirely supported by NuSMV without any syntax change. Time along paths is modeled by three operators X for a property to hold in the next state, G to hold on the entire path, F to hold eventually. The branching aspect is modeled by A, all the branches, and E, there exists a branch. A CTL operator is composed of one branching operator and one time operator. It is applied on states, or more generally on statements on the system state. 

Van der Waals Equations of State. A logical step to take next is to consider equations of state that contain both a covolume term and an attractive force term, such as the van der Waals equation. De Boer [4] and Ross and Olivier [55] have given this type of equation much emphasis. 

The next item in the loop is a decision point for possibly introducing the use of inductive reasoning methods into the deliberations. If the deductive process continues to indicate progress, then additional facts are procured or the logic tree is restructured. For example, one witness stated a particular valve was open, yet the post-incident inspection found it to be closed. The team must be careful to ensure that the valve is closed because of the actions taken prior to the incident, and not as a result of post-event response activities. The position of this particular valve may be a critical item in determining which of two scenarios is the more probable case. The incident investigation team would then initiate a short-term action item to conduct a mini-investigation to resolve this question. 

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