Shulou(Shulou.com)06/01 Report--

This article mainly introduces the relevant knowledge of pseudo-state and pseudo-state types in the behavior state machine, the content is detailed and easy to understand, the operation is simple and fast, and has a certain reference value. I believe you will gain something after reading this article on pseudo-state and pseudo-state types in the behavior state machine. Let's take a look.

Connection point reference

As mentioned earlier, the join point reference represents the reference of the sub-state machine state to the entry / exit point defined in the state machine. Join point references to sub-state machine states can be used as migration sources and migration targets. The join point reference represents the entry into the sub-state machine and the exit from the sub-state machine referenced by the quilt state machine.

A join point reference is a migration source or migration target that means an entry quilt state machine state reference that leaves the exit of the child state machine and enters the child state machine.

The entry point connection point reference as the goal of the migration means that the migration goal is the entry point pseudo state of the state machine defined in the child state machine state. As a result, the region of the sub-state machine is entered through the corresponding pseudo state of the entry point.

The exit point connection point reference as the source of the migration means that the source of the migration is the pseudo state of the exit point in the state machine defined in the child state machine state. When the sub-state machine reaches the corresponding exit point, the sub-state machine state also exits from the exit point.

Finished state

The finished state is a special state that indicates that the area that contains it has ended. That is, the migration to the finished state indicates that the behavior of the area that contains the finished state has ended.

Pseudo-state and pseudo-state types

Pseudo state is an abstraction that includes all kinds of vertices that pass instantly in the state machine diagram. Pseudo vertices are often used to connect multiple migrations into more complex composite migrations (see the instructions below). For example, by combining a migration into a bifurcated pseudo state with a set of transitions leaving the bifurcated pseudo state, a compound migration for entering an orthogonal region can be obtained.

The specific semantics of pseudo-states depend on the type of pseudo-states, which is defined by the category attribute whose type of state is PsudostateKind.

The initial-initial pseudo state represents the starting point of the region; that is, when you enter the zone in the default activation manner, it is where the activities contained in the zone begin to execute. It is at most a source of migration, which can have effective behavior, but cannot have associated trigger or guardianship conditions. There can be at most one initial vertex in an area.

Deep History-this pseudo-state is a variable that holds the state composition of the area that contains it when it was recently activated. As mentioned earlier, migrating into this pseudo-state means restoring the region to the same state composition as it did when you recently left, accompanied by all the semantics of entering the state (see the section on state entry). All entry behaviors of the restored state are performed in the appropriate order starting from the outermost state. A deep history pseudo state can only be defined in a combined state, and at most one can be defined in an area of a combined state.

Shallow history-as mentioned earlier, such a pseudo-state is a variable that holds the most recent active substate of the area that contains it. However, it does not contain the (subordinate) child state of this child state. Migrating to this pseudo-state means restoring the region to the sub-state, accompanied by the semantics of entering the state. There can be a transition that leaves the pseudo state and points to a substate in the combined state. This substate is the default shallow historical state of the combined state. A shallow historical pseudo state can only be defined in a combined state, and at most one can be defined in an area of a combined state.

Confluence-this type of pseudo state provides target vertices for two or more migrations from different vertices, while the source vertices are in different orthogonal regions. The migration terminated in the convergent pseudo state is not allowed to have guardianship conditions and trigger conditions. Similar to the rendezvous point in the Petri network, the convergence pseudo-node realizes the synchronization function, and only after all the entry migration is completed can the departure migration continue.

The bifurcation-bifurcation pseudo state divides an entry migration into two or more migrations that terminate in (different) orthogonal regions of the combined state. The migration away from the bifurcation pseudo-state can not have guardianship conditions and trigger conditions.

Join points-this type of pseudo-state is used to connect multiple transitions between states into a compound path. For example, the merge pseudo state can be used to merge multiple incoming migrations into one leaving migration, showing subsequent path sharing in this way. It can also be used to divide an entry migration into multiple departure migrations, which are selected through different guardianship constraints.

Note: such a guardianship constraint is performed before the execution of a composite migration containing this pseudo-state, which is why it is called a static conditional path.

It is possible that for a specific composite migration, the composition of the migration path and guardianship conditions makes it impossible to reach a valid state composition. In this case, the entire composite migration is invalid even if the trigger condition is valid. (as a way to avoid this situation under certain circumstances, at most one guardianship condition that is pre-defined as "else" for leaving the migration association is valid if the result of all other migrating guardianship conditions is false.) If the result of more than one guardianship condition is true, one of them will be selected, but the algorithm for making this choice is undefined.

Select-this type of pseudo state is similar to the connection point pseudo state (see previous) and has a similar purpose. One difference is that the guardianship constraint on the migration is dynamically calculated when the composite migration reaches this pseudo state. Therefore, it is selected to identify dynamic conditional branches. It allows composite migration to be divided into multiple optional branches and determines which path can be executed according to the behavior in the same composite migration before the migration reaches the selection point. If the calculus of more than one guardianship condition is true, one of the migrations will be selected, but the algorithm for making this selection is undefined. If the calculus without guardianship conditions is true, then the model is considered to be morbid. To avoid this, it is recommended to set a predefined "else" to leave the migration for all selected pseudo states.

Entry point-entry point pseudo state represents a state machine or an entry point that encapsulates a combined state of internal state / state machine. In each area of a state machine or combined state that contains an entry point, there can be at most one migration from the entry point to the vertices within the region.

Note: if the state of having an entry point is associated with an entry behavior, this behavior is performed before leaving any associated behavior of the migration. If multiple areas are called, the entry point behaves the same as the bifurcation pseudo state.

Exit point-the exit point pseudo state represents the state machine or the exit point that encapsulates the combined state of the internal state / state machine. The exit point in the region of the state machine referenced by the combined state or quilt state machine means the exit of the combined state or sub-state machine state (accompanied by the execution of the associated exit behavior). If there are multiple transitions from an orthogonal region in the state machine to this pseudo state, it behaves like a rendezvous pseudo state.

Termination-entering the termination pseudo state means that the execution of the state machine terminates immediately. The state machine does not exit any state, nor does it perform any exit behavior. Any doActivity behavior in execution is automatically aborted. Entering the termination pseudo state is equivalent to calling the delete object action.

This is the end of the article on "what are the pseudo-states and types of pseudo-states in the behavior state machine?" Thank you for reading! I believe you all have a certain understanding of the knowledge of "what are the pseudo-states and types of pseudo-states in the behavior state machine". If you want to learn more, you are welcome to follow the industry information channel.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.