Podcast
Questions and Answers
Which statement is true regarding the execution of the activity diagram?
Which statement is true regarding the execution of the activity diagram?
What can be inferred about diagrams C and D concerning their semantics?
What can be inferred about diagrams C and D concerning their semantics?
In the context of the activity diagram, what does the redundancy of flows after the decisionInput imply?
In the context of the activity diagram, what does the redundancy of flows after the decisionInput imply?
Which of the following statements about the accept events is correct?
Which of the following statements about the accept events is correct?
Signup and view all the answers
What indicates that option C is incorrect in the context of the activity diagram?
What indicates that option C is incorrect in the context of the activity diagram?
Signup and view all the answers
What is a primary purpose of submachine states in software engineering?
What is a primary purpose of submachine states in software engineering?
Signup and view all the answers
How do submachine states assist in the communication between concurrent submachines?
How do submachine states assist in the communication between concurrent submachines?
Signup and view all the answers
What does the syntax state name: name of referenced state machine diagram indicate?
What does the syntax state name: name of referenced state machine diagram indicate?
Signup and view all the answers
In the context of state machines, what is the significance of Synch state synchronization points?
In the context of state machines, what is the significance of Synch state synchronization points?
Signup and view all the answers
What happens when the attribute paidFor is set in a top submachine?
What happens when the attribute paidFor is set in a top submachine?
Signup and view all the answers
Which of the following sequences is a valid trace according to the sequence diagram?
Which of the following sequences is a valid trace according to the sequence diagram?
Signup and view all the answers
Identify the correct trace that adheres to the rules established in the sequence diagram.
Identify the correct trace that adheres to the rules established in the sequence diagram.
Signup and view all the answers
Which sequence cannot occur based on the structure of the sequence diagram?
Which sequence cannot occur based on the structure of the sequence diagram?
Signup and view all the answers
What is a possible valid sequence involving elements a, b, c, and d?
What is a possible valid sequence involving elements a, b, c, and d?
Signup and view all the answers
Which of the following sequences violates the rules of the sequence diagram?
Which of the following sequences violates the rules of the sequence diagram?
Signup and view all the answers
Determine which of these sequences is invalid.
Determine which of these sequences is invalid.
Signup and view all the answers
Select a sequence that adheres to the established order in the sequence diagram.
Select a sequence that adheres to the established order in the sequence diagram.
Signup and view all the answers
Which of the following traces is deemed acceptable?
Which of the following traces is deemed acceptable?
Signup and view all the answers
What does an action node represent in an activity flow?
What does an action node represent in an activity flow?
Signup and view all the answers
In a use case, what role does the primary actor play?
In a use case, what role does the primary actor play?
Signup and view all the answers
Which statement correctly describes a precondition for a use case?
Which statement correctly describes a precondition for a use case?
Signup and view all the answers
What is the function of a postcondition in a use case?
What is the function of a postcondition in a use case?
Signup and view all the answers
Why is execution time considered negligible for action nodes?
Why is execution time considered negligible for action nodes?
Signup and view all the answers
Which of the following best describes the role of the secondary actor in a use case?
Which of the following best describes the role of the secondary actor in a use case?
Signup and view all the answers
What does the term 'final nodes' refer to in an activity flow?
What does the term 'final nodes' refer to in an activity flow?
Signup and view all the answers
What is the purpose of the precondition in the 'PaySalesTax' use case?
What is the purpose of the precondition in the 'PaySalesTax' use case?
Signup and view all the answers
What is the primary benefit of reusing sequences in interactions?
What is the primary benefit of reusing sequences in interactions?
Signup and view all the answers
What does a gate in interaction design primarily provide?
What does a gate in interaction design primarily provide?
Signup and view all the answers
Continuations in interaction fragments allow for what specific feature?
Continuations in interaction fragments allow for what specific feature?
Signup and view all the answers
In a parallel execution context, how are the operands characterized?
In a parallel execution context, how are the operands characterized?
Signup and view all the answers
Which of the following best describes a critical region in interaction design?
Which of the following best describes a critical region in interaction design?
Signup and view all the answers
What is the behavior of a weak sequence in interaction design?
What is the behavior of a weak sequence in interaction design?
Signup and view all the answers
When referencing the LogOnRegistrar in various use cases, what benefit does it provide?
When referencing the LogOnRegistrar in various use cases, what benefit does it provide?
Signup and view all the answers
How can gates be utilized in messages for the same lifeline?
How can gates be utilized in messages for the same lifeline?
Signup and view all the answers
What type of sequence behavior is present in a critical region?
What type of sequence behavior is present in a critical region?
Signup and view all the answers
What is the implication of 'decoupling' interactions using continuations?
What is the implication of 'decoupling' interactions using continuations?
Signup and view all the answers
How is the ordered execution of a critical region notably distinct from that of parallel processing?
How is the ordered execution of a critical region notably distinct from that of parallel processing?
Signup and view all the answers
When reusing interaction sequences, what issues are most likely to be avoided?
When reusing interaction sequences, what issues are most likely to be avoided?
Signup and view all the answers
In interaction design, which aspect does a weak sequence emphasize most?
In interaction design, which aspect does a weak sequence emphasize most?
Signup and view all the answers
What is the purpose of an action node in a token movement system?
What is the purpose of an action node in a token movement system?
Signup and view all the answers
In the context of token movement, what does it mean for conditions to vary depending on node type?
In the context of token movement, what does it mean for conditions to vary depending on node type?
Signup and view all the answers
What happens when a 'send signal' action is executed?
What happens when a 'send signal' action is executed?
Signup and view all the answers
Which best describes the implicit join in action nodes?
Which best describes the implicit join in action nodes?
Signup and view all the answers
What is a significant characteristic of activity diagrams?
What is a significant characteristic of activity diagrams?
Signup and view all the answers
When does a token movement occur across an edge?
When does a token movement occur across an edge?
Signup and view all the answers
What must be true about the precondition for sending a letter in the token movement system?
What must be true about the precondition for sending a letter in the token movement system?
Signup and view all the answers
What defines a call action node?
What defines a call action node?
Signup and view all the answers
What is an outcome of the main flow at the end of the business quarter?
What is an outcome of the main flow at the end of the business quarter?
Signup and view all the answers
Which statement best describes the role of tokens in a network of nodes and edges?
Which statement best describes the role of tokens in a network of nodes and edges?
Signup and view all the answers
What is a postcondition of the sales tax payment process?
What is a postcondition of the sales tax payment process?
Signup and view all the answers
What indicates that a send signal action node is ready to execute?
What indicates that a send signal action node is ready to execute?
Signup and view all the answers
What happens when all conditions of an action node are satisfied?
What happens when all conditions of an action node are satisfied?
Signup and view all the answers
How does the movement of tokens influence the state of the system?
How does the movement of tokens influence the state of the system?
Signup and view all the answers
Study Notes
Lectures 13 and 14 - State Machines
- State machines are used to describe the behavior of complex, reactive systems.
- The 2024/2025 course covers the topic of state machines.
- State machines are valuable for understanding complex life cycles and behaviors, especially in real-time and embedded systems.
UML - State Machine Diagrams
- UML diagrams provide a visual representation of software behavior.
- State machine diagrams are a type of UML diagram that model the behavior of a reactive object.
- Subcategories of UML diagrams include structural and behavioral diagrams.
- Structural diagrams specify structure and arrangement of system components while behavioral diagrams illustrate behavior.
Originally State Charts
- State charts are based on Finite state machines, used to model large, complex, reactive systems.
- Features of state charts include:
- Broadcast (communication)
- Orthogonality (concurrency)
- Depth (abstraction, nesting of state charts)
- Memory (history mechanism)
State Charts and their role in OO Design
- The progression of different methodologies using state charts over time shows the evolution of the concept.
- Different programming languages and technologies contributed to the development and adaptation of state charts over time.
State Machines Defined During Design
- State machines are defined as part of the design workflow.
- They are used to understand complex life cycles and behaviors in a system.
- State machines should only be employed when needed, the value of using one should be considered commensurate with the complexity.
A State Diagram Models the Dynamic Behavior of a Reactive Object
- State diagrams are used to model reactive objects' dynamic behavior.
- These diagrams are useful for modeling objects with complex behaviors that are difficult to understand through other means.
- These diagrams excel when used for objects whose behavior is significantly influenced by external events.
- Interaction diagrams are more suitable for systems involving multiple objects.
Key Elements in State Machine Diagrams
- States represent conditions or situations in an object's life cycle.
- Events signal noteworthy events in time and space affecting an object's state.
- Transitions define the movement between states in response to events.
A Reactive Object Provides Context for a State Machine
- The reactive object provides the context for a state machine.
- It responds to and potentially generates internal events during its life cycle.
- Past behavior affects the current behavior of this kind of object.
State Machines Model the Behavior of Classifiers, such as…
- State machines model classifiers, such as classes, use cases, entire systems and subsystems.
Behavioral vs. Protocol State Machines
- Behavioral state machines define the implementation details of an object's behaviour.
- Protocol state machines specify the order and results of operations calls.
- Protocol state machines do not specify implementation details.
- Protocol state machines are indicated with the keyword “protocol” after the state machine name.
Example of Correspondence to Java Code
- State machines can be represented in code, providing a concrete way to perform the various actions and transitions described in the diagram.
- The use case of a lecture hall is demonstrated graphically and using a snippet of Java code to illustrate the representation and use of states and state transitions.
State is a Semantically Significant Condition of an Object
- A state in an object is a condition or characteristic during its life cycle.
- States can include performing activity or waiting for an event.
- An object can have internal transitions, sub-states and deferred events to address complex behaviours.
Actions Are Instantaneous and Uninterruptible
- Actions within a state are atomic events and cannot be interrupted.
- The entry and exit of a state are specific and defined actions, executing immediately before entering and after exiting the state.
- Internal transitions may happen without changing state.
Internal Transitions Capture That Some Transition Within the Same State Has Happened
- Internal transitions capture noteworthy events without changing an object's state, unlike external transitions.
Actions Are Instantaneous and Uninterruptible
- Actions within a state are atomic events and thus cannot be interrupted during their execution.
- Actions associated with entering or exiting a state are executed immediately upon the corresponding event occurrence.
Activities Take Finite Time to Execute and Are Interruptible
- Activities usually take finite execution time and can be interrupted by events.
- Activities differ from actions due to their finite duration and interruptibility, unlike the atomic actions.
Types of States
- Real states are normal states in a system's life cycle, while pseudo-states represent specific control points within a state machine.
- Pseudostates act as control structures for conditional behaviors and transitions.
- Initial and Terminal nodes mark the starting and ending points of the state machine behavior, for a given execution flow.
- Decision nodes enforce conditional transitions based on specific guard conditions.
- Other pseudo-states support concurrent and parallel behaviors, as well as state preservation during transitions.
Initial State
- The initial state has no incoming edges and typically one outgoing edge leading to the next state, or to a real state.
- Guard conditions are used to model multiple possible initial states.
Terminate and Final State Nodes
- A terminal node signifies the termination of a state machine, marking the end of the object's existence.
- A final state marks the conclusion of a specific sequence of states within an object, allowing an object to remain in a final state persistently.
Transitions Show Movement Between States
- Transitions illustrate the movement between states within a state machine, signifying how a given event or condition can cause a state change between two or more states.
- Transitions can have events (external or internal), conditions (guard conditions), and actions (when conditions are met).
A Transition Occurs When
- A transition occurs when an event occurs in the source state, and the associated guard condition evaluates to true.
- Execution of an action happens immediately after the event.
Transitions Have Three Optional Elements
- A transition can involve zero or more events triggering a transition (external or internal).
- A guard condition, which is a boolean expression.
- Zero or more actions associated with the transition execution.
Transitions in State Protocols Have a Slightly Different Syntax
- In protocol state machines, the guard conditions are replaced by preconditions and postconditions.
- The precondition is placed before the slash and the postcondition after.
What if the Transition Has No Event?
- Transitions without events are typically automatic transitions.
- These transitions execute when their guard or precondition conditions are true, without requiring an explicit trigger event.
Junction Pseudo-States Join or Branch Transitions
- Junction pseudo-states are control points where transitions converge or diverge.
- They can feature one or more input and output transitions managing the flow through these points.
Protect Junction Pseudo-States with Mutually Exclusive Guard Conditions
- Guards in a junction pseudo-state must be mutually exclusive, ensuring that only one output transition can be activated at a time.
The Choice Pseudo-State Directs the Flow Through the State Machine According to Guard Conditions
- The choice pseudo-state is used for handling a conditional branching behavior within a state machine, so its guard conditions must be mutually exclusive.
Attention
- The presented content highlights the nuance around evaluating guards and how the order of statements can affect the result of a state transition when multiple statements exist in a transition.
Junction Points Can Also Help Tidying Up Your Diagram, to Increase Its Understandability
- Junction points streamline complex state transition diagrams by enabling a more readable flow of state transitions from one node to another.
Events Trigger Transitions
- Events are stimuli that trigger state transitions.
- Events can initiate actions within a state and/or trigger transformations between states.
The Same Event (e.g. Checkmate), When on Different States, May Lead to Different Outcomes
- Events can lead to different outcomes based on the object's current state.
There Are Four Kinds of Events
- Call events trigger behaviors or functions within the system or on an object.
- Signal events are one-way communication without requiring a response or a return value.
- Change events trigger when a boolean expression changes value.
- Time events occur at specific points in time or after a specific duration, for instance after a specific duration.
A Call Event is a Request for a Specific Operation to be invoked on an Instance of the Context Class
- Call events initiate operations in a given object, usually with parameters to determine actions on that object.
- The operation can return a specific value.
- The return can be a successful indication of appropriate behavior on the invoked object or the opposite.
A Signal Event is a one-way Asynchronous Communication Between Objects
- Signal Events are asynchronous communication, without having to wait for response.
SimpleBankAccount Sends a Signal When Withdrawal is Rejected
- A sequence diagram shows how a bank account handles a rejected withdrawal request, delivering a signal for further processing.
A Signal Receipt Accepts the Signal as a Parameter and Leads to a New State
- A signal can be seen as a parameter in a received state action if further procedures are contingent on receiving this signal.
Change Events Occur When a Boolean Expression Changes Value from False to True
- Change events are triggered when a boolean expression changes value
- Triggered change events often involve checking the status of boolean variables.
Time Events Occur in Response to Time
- Time events are triggered at a specific time, or after a specified duration.
Composite States Dealing with Model Complexity
- Composite states represent a complex behavior that can be broken down into a combination of multiple states.
Initial and Process ARE Substates of On
- The initial and process states are nested substates within the On state.
Orthogonal States - Composite States That Contain One or More Nested Submachines
- Orthogonal states can have more nested submachines to model concurrent behaviors.
- Each region in a composite state executes concurrently, independently of each other.
Regions Are Independent, Concurrent Parts of a Composite State - They Are Activated Synchronously
- Regions within a composite state can be concurrent, executing independently until a common termination event.
Entering and Exiting Composite States
- Entering a compound state activates the initialization of all substates within its regions,
- Exiting a compound state depends on the termination of all regions within it.
Nested Substates Inherit All of the Transitions of Their Containing Superstates
- Substates inherit the transitions of the enclosing superstates.
The Final Pseudo-State of a Submachine Only Applies Within That Region
A final state within a submachine region is distinct and only impacts the associated region behavior.
Nested States Can Also Be Composite States
- Nested states can also act as composite states when their complexities increase enough, to make the diagram itself more complicated.
Entry and Exit Points: Type of Encapsulation Mechanism
- Entry and exit points enable a composite state to be encapsulated, without needing to know its internal structure.
Simple vs. Orthogonal Composite Spaces
- Simple composite states include one region.
- Orthogonal composite states include two or more regions.
Simple Composite States Contain a Single Nested State Machine
- Simple composite states have a singular and isolated state machine implementation..
Orthogonal Composite States Contain Two or More Nested State Machines That Execute Concurrently
- In orthogonal composite states, nested state machines execute concurrently, with independence within each state machine to the outermost state machine.
Example of Correspondence
- Illustrative example showing how a lecture hall state machine diagram can be represented in Java
Initializing Composite State: Synchronization Between Submachines
- The initialization step in composite states requires synchronization among states and/or submachines to ensure all states are operational before proceeding.
Monitoring Composite State: No Synchronization Between the Two Submachines
- Independent monitoring of separate components is represented in a composite state without any need for synchronization between component states.
A Submachine State References Another State Machine (Recorded in a Separate Diagram)
- A submachine state can reference another state machine defined separately in a diagram.
Consider This Machine State
- Demonstrating that state machines and submachine states can model complex state transitions, and be nested to provide more detail if necessary.
Now, We Can Reuse the VerifyingUser Submachine State
- Reuse of the VerifyingUser submachine allows to manage repetition in more complex implementations with less effort.
You Can Use Attribute Values to Communicate Asynchronously Between Concurrent Submachines
- An attribute value (e.g., an event) can trigger a transition in another concurrent submachine.
You Can Also Use Synch State Synchronization Points to Synchronize Different Regions (in Combination With Fork and Join)
- Using synch states with synchronization points facilitates synchronization and coordination of distinct but related activities within a composite state.
Memory in State Machines
- Memory in state machines refers to preserving state across transitions, allowing previous state information to impact current state and behavior based on the occurrence of events.
Shallow History
- The shallow history pseudo-state remembers the last substate visited at the same level within a composite state.
Deep History
- The deep history pseudo-state remembers the last visited substate, at or below, the same level as itself, within a composite state.
Examples with Memory (History State)
- Demonstrating usage and effect of memory features of state machines, with examples.
What Happens with H?
- The shallow history pseudo-state (H) stores the most recently active substate at the same level. The action depends on whether the condition is true or not, and if the substate was active before.
What Happens with H*?
- The deep history pseudo-state (H*) remembers the last active substate, at or below the same level, within a composite state.
Sequence of Events: e4 -> e5 -> e1
- Illustrates a sequence of events, and their relationships and the order in which they happen, with example events and their actions.
Transitions Have Three Optional Elements
- Transitions in state machines can have 0 or more events, a guard condition (a boolean expression) and actions performed upon the event triggering.
Transitions in State Protocols Have a Slightly Different Syntax
- Protocol transitions use a specialized syntax that lists preconditions before and postconditions after the events.
What if the Transition Has No Event?
- Automatic transitions execute when the associated conditions are true.
Junction Pseudo-States Join or Branch Transitions
- Junction pseudo-states handle situations where multiple transitions converge to a single point, or diverge from a single point.
Protect Junction Pseudo-States with Mutually Exclusive Guard Conditions
- Mutually Exclusive guard conditions are essential to correctly model and ensure a single outgoing transition in a junction can be chosen on each execution.
The Choice Pseudo-State Directs the Flow Through the State Machine According to Guard Conditions
- The choice pseudo-state enables conditional branching within a state machine. Each choice or case must correspond to a unique outcome.
Attention
- A warning about potential complexities in the execution order among concurrent statements that can result from using multiple statements in a transition
- Using multiple statements with conditions in a transition should be handled carefully to prevent unforeseen behavior.
Internal Transitions Capture That Some Transition Within the Same State Has Happened
- Internal transitions in state machines allow for fine-grained control over an object's behavior while using the same state.
Activities Take Finite Time to Execute and Are Interruptible
- Activities are more likely than atomic actions to be interrupted at some point.
- Activities are used to mark steps occurring over extended periods of time that are themselves composed of a series of actions.
Types of States
- The presentation introduces real and pseudo-states, specifically initial and terminal pseudo-states.
Initial State
- The initial states are the entry points for each execution flow.
Terminate and Final State Nodes
- Terminal nodes represent the conclusion of a state machine and its termination.
- Any other final state is simply the completion of an execution flow not the termination of the whole state machine.
Transitions Show Movement Between States
- Transitions detail the flow of control in a state machine.
A Transition Occurs When
- A transition fires when an event that causes the transition happens during an operational state, and when conditions (guard conditions) are also evaluated to be true.
Transitions Have Three Optional Elements
- Transitions can have multiple events triggering the transition, and conditions (guard conditions) that determine whether the transition executes or not, and actions performed.
Transitions in State Protocols Have a Slightly Different Syntax
- Protocol syntax differs from standard, typically having the precondition listed before the slash, and the postcondition after the slash.
What if the Transition Has No Event?
- Automatic transitions do not require an event to be triggered, instead they execute upon the fulfilment of the associated condition in the guard.
Junction Pseudo-States Join or Branch Transitions
- Junction states act as hubs for merging or branching transitions, allowing control of the flow based on conditions.
Protect Junction Pseudo-States with Mutually Exclusive Guard Conditions
- Guards must be mutually exclusive to prevent multiple conditions being met in a single execution.
The Choice Pseudo-State Directs the Flow Through the State Machine According to Guard Conditions
- In choice states, guard conditions are mutually exclusive, so only one path is taken.
Attention
- A warning concerning the order of statements in a sequence diagram, when guard expressions and actions are executed. Different orders among these elements can cause different results.
Junction Points Can Also Help Tidying Up Your Diagram, to Increase Its Understandability
- Junction nodes can organize and streamline complex diagrams by clarifying the flow between various transition points.
Events Trigger Transitions
- The occurrence of an event leads to a transition within the state machine, a transition being the specification for moving from one state to another.
The Same Event (e.g., Checkmate), When on Different States, May Lead to Different Outcomes
- The same event or circumstance can have qualitatively different outcomes based on the object's current state. For instance, in games this can be about winning or losing based on the state of the board.
There Are Four Kinds of Events
- Call events trigger functions to either execute or deliver data. Signal events serve as a communication mechanism between components, while change events trigger based on a change to boolean-based conditions and time events are triggered on expiry of time in milliseconds, seconds, or minutes.
A Call Event is a Request for a Specific Operation to be invoked on an Instance of the Context Class
- A call event represents the invocation of an operation in a specific object (e.g. a bank account), with inputs (parameters) providing context for performing a sequence of actions.
A Signal Event is a One-Way Asynchronous Communication Between Objects
- Signal events are asynchronous communication mechanisms without requiring a response.
SimpleBankAccount Sends a Signal When Withdrawal Is Rejected
- Illustrates a rejected withdrawal transaction using a signal event in a sequence diagram.
A Signal Receipt Accepts the Signal as a Parameter and Leads to a New State
- A signal acts as a parameter for processing an event or a series of actions depending on the signal received.
Change Events Occur When a Boolean Expression Changes Value from False to True
- Change events are triggered when a boolean expression status changes value from false to true.
Time Events Occur in Response to Time
- Time events trigger based on a time interval, either when a specified time is reached or a duration has been completed.
Composite State Dealing with Complex Behavior
- A composite state can be made up of several states, and its actions and transitions are represented within the composite state, thereby hiding more detailed information that might make a diagram less understandable if such detail is not relevant.
Initial and Process are Substates of On
- This shows that the "on" state in a state machine is a composite state, composed of initial and process states.
Orthogonal States - Composite States That Contain One or More Nested Submachines
- Represents concurrent states and distinct but interconnected activities that unfold over time, where one or more submachines exist within a main machine.
Regions Are Independent, Concurrent Parts of a Composite State - They Are Activated Synchronously
- Regions within a composite state can act independently or concurrently, and together they form the whole scope of behavior defined for the outermost or containing state, without requiring inter-dependence or specific synchronisation steps.
Entering and Exiting Composite States
- Entering a composite state activates all its constituent regions’ behaviors concurrently. Similarly, exiting a composite state depends on the termination of each one of its regions or substates.
Nested Substates Inherit All of the Transitions from Their Containing Superstates
- Substates inherit or inherit the transitions defined in the encompassing or parent states.
The Final Pseudo-State of a Submachine Only Applies Within That Region
- The final pseudo-state of a submachine only applies to the submachine or substate region, and is not a general state termination event in the sense of an overarching state machine termination.
Nested States Can Also Be Composite States
- A state within a state machine can also be a composite state, to represent the structure and behavior of complex activities.
Entry and Exit Points: Type of Encapsulation Mechanism
- Entry and exit points in composite states allow more modularity or structuring of the overall state machine behavior, without needing to know all the internal interactions or steps within a particular substate or region.
Simple vs. Orthogonal Composite Spaces
-
Simple composite states contain only one region or partition
-
Orthogonal composite states have two or more regions.
Simple Composite States Contain only a Single Nested State Machine
- A simple composite state describes a single level of state machine implementation behavior.
Orthogonal Composite States Contain Two or More Nested State Machines That Execute Concurrently
- Multiple independent state machines can exist within an orthogonal composite state, executing concurrently.
Example illustrating Use and effect of memory features in state machines
- A lecture hall example showing how memory features in state machines can influence current state behavior based on past event occurrences.
Initializing Composite State: Synchronization Between Submachines
- Describes situations in a composite state where the behaviour depends on multiple elements or regions being synchronised, or where they proceed concurrently.
Monitoring Composite State: No Synchronization Between the Two Submachines
- Illustrates how multiple independent activities are handled within a composite state, as opposed to concurrent or dependent activities.
A Submachine State References Another State Machine (Recorded in a Separate Diagram)
- A submachine state, or substate can refer to another state machine, either at a different level, and not dependent on it, but potentially requiring it for coordination or processing.
Consider This Machine State
- Example demonstrating how state machines and submachine states can model complex state transitions and how they can be nested to provide more detail; if such detail is relevant.
Now, We Can Reuse the VerifyingUser Submachine State
- Reusing the substate or submachine VerifyingUser allows for more efficient use, and potentially reduces the code involved
- The behavior associated with the submachine can be reused in other contexts, without having to repeat the individual state components.
You Can Use Attribute Values to Communicate Asynchronously Between Concurrent Submachines
- Using attributes to explicitly facilitate or coordinate communication between concurrently executing submachines within a composite state.
You Can Also Use Synch State Synchronization Points to Synchronize Different Regions (in Combination With Fork and Join)
- Use of synchronisation points and combined with fork and join to ensure that submachine states behave consistently or as anticipated.
Memory in State machines
- Memory features allow state machine behavior or transitions to change based on previous happenings or circumstances.
Shallow History
- The shallow history pseudo-state (H) remembers the last substate or region visited at the same level in a composite state.
Deep History
- Deep history pseudo-state (H*) retains memory of the last visited substate, regardless of its level within a corresponding composite state.
Examples with Memory (History State)
- Illustrative examples showcasing the usage and impact of memory features for state machine activities.
What Happens with H?
- The pseudo-state H captures the most recently active substate at the same level in the composite state and can restore this state once triggered.
What Happens with H*?
- The pseudo-state H* captures the most recently active substate, at or below the same level, in the composite state and can restore that state should the need for such a restoration or recovery of the previous state arise
Sequence of Events: e4 -> e5 -> e1
- Examples illustrating sequence diagrams and events that follow in sequence, with examples and commentary.
Transitions Have Three Optional Elements
- This explains how transitions in a state machine can include 0 or more events, a single condition (boolean expression) and actions to be executed once the transition is triggered or initiated.
Transitions in State Protocols Have a Slightly Different Syntax
- In cases where explicit protocol transitions are needed the required and/or provided interfaces and associated syntax differ slightly.
What if the Transition Has No Event?
- This section shows how automatic transitions execute when the appropriate conditions are met.
Junction Pseudo-States Join or Branch Transitions
- This section summarizes how a junction pseudo-state acts as a fusion or divergence point for transitions from other states.
Protect Junction Pseudo-States with Mutually Exclusive Guard Conditions
- Ensuring that only one or a single transition can be chosen for execution within a junction, to represent mutually exclusive conditions.
The Choice Pseudo-State Directs the Flow Through the State Machine According to Guard Conditions
- Using choice states allows modelling conditional branching in state machines or in a composite state behavior.
Attention
- A warning concerning the order of statements in a sequence diagram, when guard expressions and actions are executed. Different orders among these elements can cause different results.
Internal Transitions Capture That Some Transition Within the Same State Has Happened
- Internal transitions, while not changing state, can capture noteworthy events or intermediate steps while using the same state.
Activities Take Finite Time to Execute and Are Interruptible
- Activities usually take finite execution time, and they can be interrupted by a broader perspective of events in the containing state machine than the activity itself.
Time Events Occur in Response to Time
- This specifies how time events cause a change in state, for instance by measuring a specific time period.
Composite State Dealing with Complex Behavior
- This section details how composite states can represent multifaceted activities or complex behaviors that can be logically grouped into a single higher-order state.
Initial and Process ARE Substates of On
- This section clearly depicts how states (Initial and Process) can be structured as child states or substates of a main or parent state (the “On” state).
Orthogonal States - Composite States That Contain One or More Nested Submachines
- This section details how various activities or behaviors can either be independent or be interconnected by an encompassing or containing composite state when multiple substate/region activities or behaviors are concurrent.
Regions Are Independent, Concurrent Parts of a Composite State - They Are Activated Synchronously
- This section describes how independently executing regions within a composite state can work together.
Entering and Exiting Composite States
- Entering a composite state activates all its constituent activities (regions) concurrently. Similarly, exiting a composite state depends on the termination of all its regions or substates or activities within it.
Nested Substates Inherit All of the Transitions from Their Containing Superstates
- Substates or regions inherit the transitions of parent states or regions, but this inheritance relationship does not create interdependency.
The Final Pseudo-State of a Submachine Only Applies Within That Region
- The final state of a submachine applies only to that submachine or region and doesn't necessarily impact the overall or containing state machine.
Nested States Can Also Be Composite States
- A state within a state machine can similarly be a composite state to further break down the behavioral structure to provide more detail or to show complex interaction behavior.
Entry and Exit Points: Type of Encapsulation Mechanism
- Entry and exit points in composite states act as boundary conditions, allowing modular or structured representation of the overall state machine behavior without the need to expose all internal details.
Simple vs. Orthogonal Composite Spaces
-
Simple composite states contain only one region or partition
-
Orthogonal composite states allow for multiple or concurrently executing regions or partition activities/steps within the overall state.
Simple Composite States Contain a Single Nested State Machine
- Simple composite states describe a single level of state machine implementation or behavior.
Orthogonal Composite States Contain Two or More Nested State Machines That Execute Concurrently
- Multiple independent state machines can exist within an orthogonal composite state, executing concurrently, without the need for explicit synchronization between them.
Example illustrating Use and effect of memory features in state machines
- A lecture hall example showing how memory can impact current state behavior based on past events.
Initializing Composite State: Synchronization Between Submachines
- Describes how initialization steps in composite states can occur in tandem without creating interdependencies or in a concurrent fashion.
Monitoring Composite State: No Synchronization Between the Two Submachines
- Discusses how independent monitoring or assessment of components or sub-machines within a composite state can take place without needing overall synchronisation steps
A Submachine State References Another State Machine (Recorded in a Separate Diagram)
- Explains how one state machine can utilize the behaviors of another (presumably simplified) state machine diagram.
Consider This Machine State
- Demonstrates the use of state machines and submachine states for modelling complex transitions or behaviors
Now, We Can Reuse the VerifyingUser Submachine State
- Example that illustrates how submachines or substates make working with complex behaviours or actions in state machines more straightforward.
You Can Use Attribute Values to Communicate Asynchronously Between Concurrent Submachines
- Shows how attribute values can be used to communicate between concurrent activities or submachine states in a composite state.
You Can Also Use Synch State Synchronization Points to Synchronize Different Regions (in combination with fork and join)
- How using synchronisation points can make the behaviour of the various different activities or submachine regions and their interdependence and sequencing more explicit.
Memory in State machines
- Memory features allow for the state machine behavior, or states transitions, to change based on past circumstances.
Shallow History
- Defines how shallow history pseudo-state (H) can act. The shallow history pseudo-state (H) remembers the last substate or region visited at the same level in a composite state.
Deep History
- Defines how deep history pseudo-state (H*) can act. Deep history pseudo-state (H*) retains memory of the last visited substate, at or below the same level, within a composite state.
Examples with Memory (History State)
Illustrative examples demonstrating the usage and effect of the memory features in activities.
What Happens with H?
- Shallow history pseudo-state (H) captures the most recently active substate at the same level within a composite state and can restore the state should the need arise
What Happens with H*?
- Deep history pseudo-state (H*) remembers the last active substate, at any or below the same level. The restored state may be different for a different cause and/or conditions.
Sequence of Events: e4 -> e5 -> e1
- Illustrative example sequence diagrams that follow events following one after the other in terms of temporal ordering or precedence.
Internal transitions Capture that Some Transition within the Same State Has Happened
- Explains that internal transitions show event-driven behavior, without changing from one state to another state, if a condition for switching states is not fulfilled.
Activities- Take Finite Time to Execute and are Interruptible
- Activities are actions requiring finite duration and can be interrupted.
Time Events Occur in Response to Time
- Time events are triggered at a specific time, or after a specific duration of time has passed in a state machine.
Composition states dealing with model complexity
- Composite states that present the structure or behavior of complex activities and actions or activities.
Initial and Process states are substates of On
- Demonstrates how initial and process states or regions can be child or substates in a parent state (the “On” state).
Orthogonal states - composite states that contain one or more nested submachines
- Orthogonal states represent concurrent composite behaviors or activities within an encompassing or parent composite state.
Regions are independent, concurrent parts of a composite state - they are activated synchronously
- Describes how regions (activities) within a composite act independently but concurrently, or in some cases in tandem, without the need of explicit synchronization steps.
Entering and Exiting Composite States
- Describes how entering a composite state activates concurrent behavior and exiting the composite state completes the execution flow for all parallel contained regions.
Nested Substates Inherit all of the transitions from their containing superstates
- Substates in a composite state inherit the transitions of their containing superstates or regions which do not need to be explicitly written.
The final pseudo-state of a Submachine only applies within that region
- The final state of a submachine only affects the associated region or submachine and doesn't impact the overall or enclosing state machine.
Nested States can also be composite states
- Shows how states within a state machine can also act or be structured as composite states or activities, to provide fine-grained structure, or to break down complex behavioral patterns or behaviors.
Entry and Exit Points: Type of Encapsulation Mechanism
- Displays how entry and exit points can enhance the modularity of a composite state without needing to understand all the inner states within it.
Simple vs. Orthogonal Composite Spaces
-
A simple composite state has a singular region
-
An orthogonal composite state has multiple, independent regions.
Simple Composite States Contain only a Single Nested State Machine
- Simple composite states represent a single level of state machine behavior.
Orthogonal Composite States Contain Two or More Nested State Machines That Execute Concurrently
- Multiple independent state machines can exist within an orthogonal composite state, executing concurrently, without external or explicit synchronization between them.
Example illustrating Use and effect of memory features in state machines
- Illustrates an example sequence diagrams that show how the use and effect of memory features in activities can change the current state behavior based on past events or circumstances encountered.
Initializing Composite State: Synchronization Between Submachines
- Illustrates the concurrent initialization of submachines without explicit synchronization required
Monitoring Composite State: No Synchronization Between the Two Submachines
- Illustrates how the monitoring of submachines can be designed without requiring synchronization steps.
A Submachine State References Another State Machine (Recorded in a Separate Diagram)
- Illustrates how one state machine can incorporate the behaviours of another (usually simplified) state machine diagram
Consider This Machine State
- Illustrates the inclusion of submachine states and state machines to represent complex activities and states.
Now, We Can Reuse the VerifyingUser Submachine State
- Reusing a substate or submachine (e.g. VerifyingUser) simplifies complex systems by reusing its behavior in other related use cases.
You Can Use Attribute Values to Communicate Asynchronously Between Concurrent Submachines
- Shows how attributes can mediate or facilitate inter-communication between concurrently running substates within composite states.
You Can Also Use Synch State Synchronization Points to Synchronize Different Regions (in combination with fork and join)
- Using synchronisation points and the combination of fork and join operations ensures that substates within a composite exhibit synchronized behavior.
Memory in State Machines
- Memory features allow state machine behavior to change based on past occurrences.
Shallow History
- Remembers and restores the most recently active substate at the same level of a composite state.
Deep History
- Retains the most recently active state at or below the same level in the composite state.
Examples with Memory (History State)
- Demonstrating examples to showcase use and impact of memory features on state machine activities.
What Happens with H?
- The shallow-history state (H) captures the most recently active substate at the same level. Behavior is restored upon activation of the substate.
What Happens with H*?
- The deep-history pseudo-state (H*) remembers the last visited subordinate state or substate irrespective of level, relative to the composite state.
Sequence of Events: e4 -> e5 -> e1
- Demonstrates a sequence of events (e4 -> e5 -> e1) in a diagram, along with a table of events, states, and commentary.
Transitions Have Three Optional Elements
- Explains detailed information about possible transition events, including multiple event triggers, conditions to satisfy, and actions to be taken.
Transitions in State Protocols Have a Slightly Different Syntax
- Protocol transitions employ precondition and postcondition listings, preceding and following the event/command respectively.
What if the Transition Has No Event?
- This describes how and when (upon fulfilment of associated conditions) an automatic transition occurs.
Junction Pseudo-States Join or Branch Transitions
- Clarifies how pseudo-states representing merging or branching points facilitate control over sequencing in an overall or composite state.
Protect Junction Pseudo-States with Mutually Exclusive Guard Conditions
- Emphasizes how mutually exclusive guard conditions help ensure a unique or chosen output transition from a junction in a state machine.
The Choice Pseudo-State Directs the Flow Through the State Machine According to Guard Conditions
- Shows how choice pseudo-states are used for conditional branching, emphasizing mutual exclusiveness of guard conditions to model unique conditional paths.
Attention
- A warning about complexity in a sequence diagram when guard expressions or actions are multiple in a transition. Different execution orders among these elements can lead to different outcomes, thus should be handled carefully.
Internal Transitions Capture That Some Transition Within the Same State Has Happened
- Internal transitions in state machines model significant happenings within states, without requiring the change of state to another distinct one.
Activities Take Finite Time to Execute and Are Interruptible
- Activities comprise a sequence of actions occurring over an extended time period, and therefore can be interrupted or paused by other external actions or situations.
Time Events Occur in Response to Time
- Explains how time events trigger transitions based on specified conditions or on a particular relative or absolute time value.
Composite states dealing with model complexity
- Composite states manage more complex activities, breaking down or splitting a larger activity into smaller and more manageable components or sub-activities.
Initial and Process states are substates of On
- Illustrates how "on" state can have nested substates ("Initial" or "Process")
Orthogonal States - Composite States That Contain One or More Nested Submachines
- Shows how distinct "competing" or independent activities can be run in parallel without interfering with each other within a composite state.
Regions are
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Test your knowledge on the intricacies of activity diagrams and state machines in software engineering. This quiz covers key concepts such as submachine states, decision flows, and sequence diagram traces. Explore your understanding of these essential components and their implications in system design.
