UNIT-4

Behavioral Diagrams

P. P. Mahale

Behavioral Diagrams

• Use Case Diagram – high-level behaviors of the system, usergoals, external entities: actors

• Sequence Diagram – focus on time ordering of messages

• Collaboration Diagram – focus on structural organization ofobjects and messages

• State Chart Diagram – event driven state changes of system

• Activity Diagram – flow of control between activities

Use case Diagram

• A use case diagram is a diagram that shows a set of use cases and actors and their relationships.

Common Properties

• A use case diagram is just a special kind of diagram and sharesthe same common properties as do all other diagrams a name andgraphical contents that are a projection into a model.

Use case DiagramContents

• Use case diagrams commonly contain

• Use cases

• Actors

• Dependency, generalization, and association relationships

Common Uses

1. To model the context of a system

2. To model the requirements of a system

Terms and Concepts

• A use case diagram is a diagram that shows a set of use cases and actors and their relationships.

Names

• Every use case must have a name that distinguishes it from other use cases. A name is a textual string.

Figure Simple and Path Names

Use case Diagram

Use Cases and Actors

• An actor represents a coherent set of roles that users of use casesplay when interacting with these use cases. Typically, an actorrepresents a role that a human, a hardware device, or even anothersystem plays with a system.

Figure : Actors

Use case Diagram

Use Cases and Flow of Events

A use case describes what a system does but it does not specify how itdoes it.

You can specify the behavior of a use case by describing a flow ofevents in text clearly enough for an outsider to understand it easily.

• For example, in the context of an ATM system, you might describe the use case Validate User in the following way:

• Main flow of events:

• Exceptional flow of events:

Use case Diagram

Use Cases and Scenarios

• A scenario is a specific sequence of actions that illustrates behavior.

Use Cases and Collaborations

• As Figure shows, you can explicitly specify the realization of a use case by a collaboration.

Figure : Use Cases and Collaborations

Use case Diagram

Organizing Use Cases

• You can organize use cases by grouping them in packages in the same manner in which you can organize classes.

Figure : Generalization, Include, and Extend

Use case Diagram

Use case Diagram

Interaction Diagrams• Sequence diagrams and collaboration diagrams both of which are

called interaction diagrams

Sequence Diagrams

• A sequence diagram emphasizes the time ordering of messages.

Figure : Sequence Diagram

• Sequence & collaboration are call interaction diagram used formodeling dynamic aspect of system

• It represent interaction, consist of set of objects & theirrelationships including message

1. Sequence diagram is an interaction diagram that shows timeordering of messages

2. Collaboration diag. is an interaction diagram that shows structuralorganization of object that send & receive message

• Model particular flow of control of use case

Interaction Diagrams

• Graphically sequence diagram is table that shows objects arranged in x-axis & messages ordered in increasing time along y-axis

• Graphically collaboration diagram is collection of vertices & arcs

Common properties of interaction diagram :

- Share common properties such as name & graphical content

- Content of interaction diagram :

1. Object

2. Link

3. Messages

- Also contains notes & constraints

1. Sequence diagram :-

- Shows time ordering

- Formed by placing objects that participate in interaction at top of diagram

- Place object that initiate interaction at the left & increasingly moresubordinate objects to right

- Place message that these object send & receive along y-axis in order ofincreasing time from top to bottom

- 2 feature that distinguish from collaboration

1. There is object life line:

- It is vertical dashed line that represent existence of an object over aperiod of time

- Object are aliened at top with their life line dawn from top to bottom

2. There is focus of control

- It is tall, thin, rectangular that shows period of time in which an objectperform an action

- Top of rectangle is aliened with start of action, bottom with completion

2. Collaboration Diagram

- It shows structural organization of object that participate in interaction

- It formed by placing object that participate in interaction as vertices in

graph

- show link that connect these object as arc

- Show message that object send & receive

Collaboration Diagrams

• A collaboration diagram emphasizes the organization of theobjects that participate in an interaction.

Figure : Collaboration Diagram

Interaction Diagrams

Timing Diagrams

• Timing diagrams are a special representation of interactions thatfocus on the specific timings of messages sent between objects.

• You can use timing diagrams to show detailed time constraints onmessages or to show when changes occur within lifelines withrespect to time.

• Timing diagrams are most often used with real-time or embeddedsystems.

Interaction Diagrams

Figure : Simple timing diagram

Interaction Diagrams

Figure : Timing diagram with tick marks

Interaction Diagrams

Figure : Timing diagram with time constraints

Interaction Diagrams

Figure : Timing diagram with multiple lifelines andmessages

Interaction Diagrams

Figure : Timing diagram using a simpler timeline notation

Interaction Diagrams

Communication diagrams

• In UML 2.0 communication diag. is a simplified version of UML 1.x collaborationdiag.

• 4 –type of interaction diag.:

- Sequence diagram

- Communication diagram

- Interaction overview diagram

- Timing diagram

• Model interaction between object

• Communication diag. represent combination of info. Taken from class, sequence,use case diag. describing both static & dynamic behavior of system

• It shows message flow between objects in OO application & also imply basicassociation between classes

State chart Diagram

State chart Diagram• UML has two types of state machines:

Behavioral state machines

• Show the behavior of model elements such as objects.

• A behavioral state machine represents a specific implementation ofan element.

Protocol state machines

• Show the behavior of a protocol. Protocol state machines show howparticipants may trigger changes in a protocol's state and thecorresponding changes in the system (i.e. The new state of theprotocol).

Behavioral State Machines

You can model the behavior of the classifier using states,pseudostates, activities and transitions .

Protocol State Machines

States• States model a specific moment in the behavior of a classifier. This

moment in time is defined by some condition being true in theclassifier.

• A state is shown as a rectangle with rounded corners. The name ofthe state is written inside the rectangle.

Figure A simple state

• A state name may be placed outside of the rectangle in a tab notationwhen showing composite or submachine states

Figure : A state with its name in a tab

• Within the rectangle a state can be divided into compartmentsas needed. UML defines the following compartments:

Figure : A state with compartments

UML defines three types of states:

1. Simple states

• Simplest of all states, they have no substates. All the example statesused so far in this section are simple states.

2. Composite states

• Have one or more regions for substates. A composite state with twoor more regions is called orthogonal .

3. Submachine states

• Semantically equivalent to composite states, submachine states havesubstates that are contained within a substate machine . Unlikecomposite states, submachine states are intended to group states, soyou can reuse them.

Composite States

Figure : A composite state with Figure: Composite state with

one region composite icon

• Regions• A region is shown using a dashed line dividing the decomposition

compartment. You may name each region by writing its name withinthe region's area.

• Figure shows a composite state with two regions.

Submachine state• A submachine state is shown in the same rounded rectangle as any

other state, except you show the name of the state, followed by acolon (:) followed by the name of the referenced submachine.

• Figure shows a submachine state.

Transitions

• A transition shows the relationship, or path, between two statesor pseudostates.

• It represents the actual change in the configuration of a statemachine as it heads from one state to the next.

• Transitions are shown as a line between two states, with anarrowhead pointing to the destination state.

Transitions• When the action or activity of a state completes, flow of control passes

immediately to the next action or activity state.

• You specify this flow by using transitions to show the path from one action oractivity state to the next action or activity state. In the UML, you represent atransition as a simple directed line, as Figure shows.

• Trigger less transitions may have guard conditions, meaning that such atransition will fire only if that condition is met;

trigger [guard] / effect

where:

Trigger

• Indicates what condition may cause this transition to occur. The trigger istypically the name of an event, though it may be more complex.

Guard

• Is a constraint that is evaluated when an event is fired by the state machineto determine if the transition should be enabled. Guards should not haveany side effects and must evaluate to a Boolean. Guards will always beevaluated before a transition is fired.

Effect

• Specifies an activity that is executed when a transition happens. Thisactivity can be written using operations, attributes, and links of the owningclassifier as well as any parameters of the triggering event. An effectactivity may explicitly generate events such as sending signals or invokingoperations.

Transition types

• Compound transition: A representation of the change from onecomplete state machine configuration to another.

• High-level transition: A transition from a composite state.

• Internal transition: A transition between states within the samecomposite state.

• Completion transition: A transition from a state that has noexplicit trigger. When a state finishes its do activities, a completionevent is generated.

Signal Symbols

• Transitions may be shown in more detail using explicit icons toshow signal sending, signal receipt, and effect activities.

Figure A transition-oriented view showing a signal being received

Activities• An activity represents some functionality that is executed by a system.

• Each activity has a label showing when the activity executes, and anoptional activity expression. An activity is written as:

label / activity expression

• You can write an activity expression using pseudo code:

list.append(keystroke) ; print("*")

or natural language: record keystroke and show password character

UML reserves three activity labels:

• Entry: Triggers when a state is entered.

• Exit: Triggers when leaving a state.

• Do: Executes as long as a state is active.

Protocol State Machines

• Protocol state machines capture the behavior of a protocol, such asHTTP or a challenge response speak easy door.

• Protocol state machines differ from behavioral state machines in thefollowing ways:

• entry, exit, and do activities can't be used.

• States can have invariants. Place invariants in square brackets underthe state name.

• The keyword protocol is placed in curly braces after the state machinename to indicate the state machine is a protocol state machine.

• Transitions in protocol state machines have a precondition, the trigger,and a post condition. The notation for a protocol transition is as follows:

[precondition ] event / [postcondition ]

• Each transition is associated with zero or one operation on the owningclassifier.

• Figure shows a simplified version of the Simple Mail Transport Protocol(SMTP) protocol.

Pseudostates

Pseudostates are special types of states that represent specificbehavior during transitions between regular states.

Event Processing Information within a state machine is conveyed via events.

1. Dispatch

• As events are triggered, they are added to an event pool. Once added tothe event pool, events are sent out for processing by the state machineor are dispatched .

• The order of event dispatch and processing isn't specified by UML. Thisallows state machines to impose their own prioritization schemes onevents if desired.

2. Deferred Events

• You can list events that should be deferred from dispatching while in agiven state. You show a deferred event by listing the event, followed by aforward slash and the keyword defer within the state.

• Figure shows a state that defers the cancel event. If the cancel eventdoes fire, it is held in the event pool until the state machine leaves thisstate.

Activity Diagrams

Terms and Concepts An activity diagram shows the flow from activity toactivity.

Common Properties An activity diagram is just a special kind of diagramand shares the same common properties as do all other diagrams aname and graphical contents that are a projection into a model. Whatdistinguishes an interaction diagram from all other kinds of diagrams isits content.

Contents :

Activity states and action states

Transitions

Objects

Action States and Activity States

• In the flow of control modeled by an activity diagram, things happen. Youmight evaluate some expression that sets the value of an attribute or thatreturns some value.

• Alternately, you might call an operation on an object, send a signal to anobject, or even create or destroy an object. These executable, atomiccomputations are called action states because they are states of the system,each representing the execution of an action.

Figure :Action States

Branching

• You can include a branch, which specifies alternate paths taken basedon some Boolean expression.

• As Figure shows, you represent a branch as a diamond. A branch mayhave one incoming transition and two or more outgoing ones.

• On each outgoing transition, you place a Boolean expression, which isevaluated only once on entering the branch

Forking and Joining

• When you are modeling workflows of business processes, you mightencounter flows that are concurrent.

• In the UML, you use a synchronization bar to specify the forking and joiningof these parallel flows of control.

• A synchronization bar is rendered as a thick horizontal or vertical line.

• For example, consider the concurrent flows involved in controlling an audio-animatronic device that mimics human speech and gestures.

• As Figure shows, a fork represents the splitting of a single flow ofcontrol into two or more concurrent flows of control.

• A fork may have one incoming transition and two or more outgoingtransitions, each of which represents an independent flow of control.

• Join represents the synchronization of two or more concurrent flows ofcontrol.

• A join may have two or more incoming transitions and one outgoingtransition

Swimlanes

• Useful, especially when you are modeling workflows of businessprocesses, to partition the activity states on an activity diagram intogroups

• Each group representing the business organization responsible for thoseactivities.

• In the UML, each group is called a swimlane because, visually, eachgroup is divided from its neighbor by a vertical solid line.

• A swimlane specifies a flows of activities.

• Each swimlane has a name unique within its diagram

Object Flow

• Objects may be involved in the flow of control associated with anactivity diagram

• As Figure shows, you can specify the things that are involved inan activity diagram by placing these objects in the diagram,connected using a dependency to the activity or transition thatcreates, destroys, or modifies them.

• This use of dependency relationships and objects is called anobject flow because it represents the participation of an object ina flow of control.

• In addition to showing the flow of an object through an activitydiagram, you can also show how its role, state and attributevalues change.

• As shown in the figure, you represent the state of an object bynaming its state in brackets below the object's name.

• Similarly, you can represent the value of an object's attributes byrendering them in a compartment below the object's name.

Figure Object Flow