Unit 3(advanced state modeling & interaction meodelling)
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UNIT – 3
ADVANCED STATE MODELING, INTERACTION MODELING:
State Modeling: Nested state diagrams; Nested states; Signal Advanced generalization; Concurrency; A sample state model; Relation of class and state models; Practical tips. Interaction Modeling: Use case models; Sequence models; Activity models. Use case relationships; Procedural sequence models; Special constructs for activity models.
Two major features are introduced for controlling complexity and combinatorial explosion in state diagrams◦ Nested state diagrams◦ Concurrent state diagrams
Many other features are also added◦ propagated transitions◦ broadcast messages◦ actions on state entry, exit◦ …
S2
S1
Nested State Diagrams
Concurrent State Diagrams
Activities in states are composite items denoting other lower-level state diagrams
A lower-level state diagram corresponds to a sequence of lower-level states and events that are invisible in the higher-level diagram.
When one state is complex, you can include substates in it.◦ drawn as nested rounded
rectangles within the larger state
Caution: Don't over-use this feature.◦ easy to confuse separate states
for sub-states within one state
superstate
substates
A state may be represented as nested substates.◦ In UML, substates are shown by nesting them in a superstate box.◦ A substate inherits the transitions of its superstate.
Idle
off hook / play dial tone
on hook
Active[valid subscriber]
PlayingDialTone
Dialing Connecting
digitdigit
complete
Talking
connected
Simple State
Complex State
Substate1
entry: entry action
Substate2
Substate1
entry: entry action
Substate2
event( args )[ cond ] / action t̂arget.event(args)event( args )[ cond ] /
action t̂arget.event(args)
event( args )[ cond ] / action t̂arget.event(args)
event( args )[ cond ] / action t̂arget.event(args)
Super-state
A Bevent-1
C
event-2
A B
C
event-1
event-2event-2
Checking
do / check Item
Dispatchingdo / initiate delivery
Delivering
[all items checked && some items not in stock]Order item
[all items checked && all items available]Dispatch items
[all items ava
ilable]
Item re
ceived
delivery
get first item
Cancelingcancelled
Ordering
Exit/ Item receiveddo / order Item
*[all items checked]get next item
entry / deliver Items
do / Remove Item
Transitions can be specific◦ A transition can be from a specific
substate (T1)◦ A transition can be to a specific
substate inside the nested state (T2) Transitions can be general◦ We saw that a transition from the
superstate is valid for all substates (T3)◦ A transition into the superstate (T4)
normally goes to the default initial state (start state leading to F)
T1
S
A B
E
F
CD
T2T4
T3
◦ concurrency is a property of systems in which several computations are executing simultaneously, and potentially interacting with each other.◦ Dashed line indicates that an order is in two different states, e.g. Checking &
Authorizing◦ When order leaves concurrent states, it’s in a single state: Canceled, Delivered
or Rejected
◦ Concurrent Sub states - Used when two or more state diagrams are executing concurrently within a single object.
Complex systems usually have concurrency◦ “subsystems” that operate (mostly)
independently Heart monitor device◦ The power supply and the heart
monitoring application are really concurrent subsystems◦ They should be modeled that way!!◦ They are mostly independent: the
monitoring application doesn’t care where it gets its power
Heart Monitor
MonitoringSubsystem
PowerSubsystem
Startup
Alarm
Operational
Off
Switch on
Switch offStartup
Complete
Problemdetected
Running
Monitoring Subsystem
MainsBattery
Mains off
Mains on
Dotted lineseparatesconcurrent statemachines
Power Subsystem
release keyturn key to startIgnition
turn key off
[Transmissionin Neutral]
depress accelerator
release accelerator
Accelerator
Transmissionpush R
push N
push Fpush N
upshift
downshift
upshift
downshift
stopForward
depress brake
release brake
Brake
Car
off starting on
Neutral Reverse
first second third
onoff onoff
Two types of concurrency1. System concurrency◦ State of overall system as the aggregation of state diagrams, one
for each object. Each state diagram is executing concurrently with the others.
2. Object concurrency◦ An object can be partitioned into subsets of states (attributes and
links) such that each of them has its own subdiagram. ◦ The state of the object consists of a set of states: one state from
each subdiagram.◦ State diagrams are divided into subdiagrams by dotted lines.
The class model describes the class & objects in a system and their relationship.
The state model describes the life cycles of the objects.
The interaction model describes how the objects interact.
The interaction model starts with use cases that are then elaborated with sequence and activity diagrams
Use case: focuses on functionality of a system- i.e, what a system does for users
Sequence diagrams: shows the object that interact and the time sequence of their interactions
Activity diagrams: elaborates important processing steps
Functional vs. Non-Functional
Requirements
Functional
Non-Functional
Functional requirement are user ‘visible’ features and aretypically initiated by stakeholders of the system – generate report, login, etc.
Non-functional requirements are ‘non-visible’ features and but required for a effective running of an application – security, backup, etc.
Use Case diagrams show the various activities the users can perform on the system.
◦ System is something that performs a function.
They model the dynamic aspects of the system.
Provides a user’s perspective of the system.
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A use case is a model of the interaction between External users of a software product (actors) and The software product itself
More precisely, an actor is a user playing a specific role describing a set of user scenarios capturing user requirements contract between end user and software developers
Use case diagrams are used to visualize, specify, construct, and document the (intended) behavior of the system, during requirements capture and analysis.
Provide a way for developers, domain experts and end-users to Communicate.
Serve as basis for testing.
Use case diagrams contain use cases, actors, and their relationships.
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Actors: A role that a user plays with respect to the system, including
human users and other systems. e.g., inanimate physical objects (e.g. robot); an external system that needs some information from the current system.
Use case: A set of scenarios that describing an interaction between a user and a system, including alternatives.
System boundary: rectangle diagram representing the boundary between the actors and the system.
Association: Communication between an actor and a use case; Represented by a solid line.
Actors
Could be human beings, other systems, timers and clocks or hardware devices.
Actors that stimulate the system and are the initiators of events are called primary actors (active)Actors that only receive stimuli from the system are called secondary actors (passive)
Actors
Who/what will be interested in the system?
Who/what will want to change the data in the system?
Who/what will want to interface with the system?
Who/what will want information from the system?
1. Avoid showing communication between actors.
2. Actors should be named as singular. i.e student and NOT students. NO names should be used – i.e John, Sam, etc.
1. Start by identifying the actors of the system
2. Define the goals of the system and how they can be achieved using the systems’ actors
3. Illustrate these goals and actors actions using use-case diagram(s)
37
A use case describes a sequence of actions a system performs to yield an observable result or value to a particular actor
Naming convention = verb + noun (or) verb + noun-phrase, ◦ e.g. withdraw cash
A good use case should:◦ Describe a sequence of transactions performed by a system that
produces a measurable result (goal) for a particular actor◦ Describe the behavior expected of a system from a user's
perspective◦ Enable the system analyst to understand and model a system from
a high-level business viewpoint◦ Represent the interfaces that a system makes visible to the
external entities and the interrelationships between the actors and the system
38
Use case is a particular activity a user can do on the system.
Is represented by an ellipse.
Following are two use cases for a library system.
39
ReserveBorrow
• What are the tasks of each actor?• Will any actor create, store, change, remove, or read
the information?• Will any actor need to inform the system about the
sudden, external changes?• Does any actor need to informed about certain
occurrences in the system?• What use cases will support and maintain the system?• Can all functional requirements be performed by the
use cases?
Construct Description Notation
Use-case A sequence of transactions performed by a system that produces
a measurable result for a particular actor
Actor A coherent set of roles that users playwhen interacting with these use cases
System Boundary
The boundary between the physical system and the actors who interact with the physical system
42
• Functionality provided by the system• Consist of a series of steps which collectively add
value to the user of the system• Examples
– Issue a book to a member– Receive a book back from a member– Query the current location of a book– Maintain member’s information– Maintain book’s information
47
Actor
Association System boundary
Use-case
System name
48A Library System.
client employee
supervisor
library system
borrow
reserve
Order title
Fine payment
49
Teacher
Student
Printing administrator
Grade system
Record grades
View grades
DistributeReport cards
Create report cards
Extend: a dotted line labeled <<extend>> with an arrow toward the base case. The extending use case may add behavior to the base use case. The base class declares “extension points”.
<<extend>>
Include: a dotted line labeled <<include>> beginning at base use case and ending with an arrows pointing to the include use case. The include relationship occurs when a chunk of behavior is similar across more than one use case. Use “include” in stead of copying the description of that behavior.
<<include>>
The base use case explicitly incorporates the behavior of another use case at a location specified in the base.
The included use case never stands alone. It only occurs as a part of some larger base that includes it.
ניתוח מערכות מידע 53
base included<<include>>
Enables to avoid describing the same flow of events several times by putting the common behavior in a use case of its own.
ניתוח מערכות מידע 54
updatinggrades
outputgenerating
verifyingstudent id
<<include>>
<<include>>
Include relationships are used when two or more use cases share some common portion in a flow of events
This common portion is then grouped and extracted to form an inclusion use case for sharing among two or more use cases
Most use cases in the ATM system example, such as Withdraw Money, Deposit Money or Check Balance, share the inclusion use-case Login Account
56
57
Login Account
(Included use case)
Withdraw Money
(Base use case)
58
The base use case implicitly incorporates the behavior of another use case at certain points called extension points.
The base use case may stand alone, but under certain conditions its behavior may be extended by the behavior of another use case.
ניתוח מערכות מידע 59
base extending<<extend>>
In UML modeling, you can use an extend relationship to specify that one use case (extension) extends the behavior of another use case (base)
This type of relationship reveals details about a system or application that are typically hidden in a use case
60
61
Process Excess Amount (Extending use case)
Withdraw Money (Base use case)
If condit ional guard is true, extending f low is executed
62
Slide 2 (of 48)
Figure 16.12
Generalization.
ניתוח מערכות מידע 65
student
non-graduatestudent
graduatestudent
Construct Description Notat ion
Associat ion The participation of an actor in a use case, i.e. an instance of an actor and instances of a use case communicating with each other
Generalization A taxonomic relationship between a general use case and a more specific use case. The arrow head points to the general use case
Extend A relationship between an extension use case and a base use case, specifying how the behavior of the extension use case can beinserted into the behavior defined for the base use case. The arrow head points to the base use case
66
Construct Description Notation
Include A relationship between a base use case and an inclusion use case, specifying how the behavior for the inclusion use case is inserted into the behavior defined for the base use case. The arrow head points to theinclusion use case
67
Both Make Appointment and Request Medication include Check Patient Record as a subtask (include)
The extension point is written inside the base case Pay bill; the extending class Defer payment adds the behavior of this extension point. (extend)
Pay Bill is a parent use case and Bill Insurance is the child use case. (generalization)
(TogetherSoft, Inc)
Each use case may include all or part of the following:
Title or Reference Name - meaningful name of the UC Author/Date - the author and creation date Modification/Date - last modification and its date Purpose - specifies the goal to be achieved Overview - short description of the processes Cross References - requirements references Actors - agents participating Pre Conditions - must be true to allow execution Post Conditions - will be set when completes
normally Normal flow of events - regular flow of activities Alternative flow of events - other flow of activities Exceptional flow of events - unusual situations Implementation issues - foreseen implementation
problems
ע יד
מת
כוער
מח
תוני
73
The sequence model elaborates the themes of use cases.
Two kinds of sequences models
Scenarios
Sequence diagram
A scenario is a sequence of events that occurs during one particular execution of a system.
For example:John logs in, transmits a message from John to the
broker system.
A sequence diagram shows the participants in an interaction and the sequence of messages among them.
A sequence diagram shows the interaction of a system with its actors to perform all or part of a use case.
Each use case requires one or more sequence diagrams to describe its behaviour.
Sequence diagrams, also known as event diagrams or event scenarios, illustrate how processes interact with each other by showing calls between different objects in a sequence.
These diagrams have two dimensions:
The vertical lines show the sequence of messages and calls in chronological order
Horizontal elements show object instances where the messages are relayed.
Components Of A Sequence Diagram
Sequence Diagram
MessagesActive objects
Activation Box LifelineControl Information
Active Objects:◦ Any objects that play a role in the system◦ Can be any object or class that is valid within the system◦ Can be an Actor that is external to the system and derives benefits
from the systemMessages:◦ Used to illustrate communication between different active
objects.◦ Used when an object needs
to activate a process of a different object to give information to another object
Lifeline◦ Denotes the life of actors/objects over time during a sequence
Focus of control (activation box)◦ Means the object is active and using resources during that time
period
Control information◦ Shows the control flow in the system◦ Creation and destruction of an object through <<create>> and
<<destroy>>
Squares with object type, optionally preceded by object name and colon◦ write object's name if it clarifies the diagram◦ object's "life line" represented by dashed vert. line
84
Objects are displayed at the top of the diagramThe vertical dimension represents timeEach object has a dashed line – lifeline – extending below it – to indicate the period of time during which objects playing that role actually exist
Object Name
Creation: arrow with 'new' written above it
Deletion: an X at bottom of object's lifeline
86
The messages in an interaction are drawn from top to bottom, in the order that they are sent. Messages are shown as arrows pointing from the lifeline of the role sending the message to the lifeline of the receiver. When a message is sent, control passes from the sender of the message to the receiver.
Object Name Object Name
message
Return of control is shown using dashed arrow returning to the calling object.
Object Name Object Name
message
Message (method call) indicated by horizontal arrow to other object◦ write message name and arguments above arrow
89
Activations - show when a method is active – either executing or waiting for a subroutine to return
◦ Either that object is running its code, or it is on the stack waiting for another object's method to finish
90
• Period of time during which an object is processing a message, Shown on a lifeline as a narrow rectangle whose top is connected to a message.
• When an object finishes processing a message, control returns to the sender of the message
Object Name Object Name
message
a : Assembly part : CatalogEntry
getNumber()
: Client
count(part)
return number
Lifeline
Activation(optional)
Messages
control returns to the sender of the message (optional)
Caller Phone Recipient
Picks up
Dial tone
Dial
Ring notification Ring
Picks up
Hello
Activity diagrams and use cases are logical model which describe the business domain’s activities without suggesting how they are conduct.
A diagram that emphasizes the flow of control from activity to activity in an object.
Similar to the traditional program flowchart.
Used to provide detail for complex algorithms.
Primary activities and the relationships among the activities in a process.
Purpose
◦ to model a task (for example in business modelling)
◦ to describe a function of a system represented by a use case
◦ to describe the logic of an operation
◦ to model the activities that make up the life cycle in the Unified Process
Initial Node Control Flow Action or Activity Object Flow Branch
Merge
Fork Join
Final Node
09/29/14 99
This represents the start of the flow of an activity diagram.
An activity diagram contains a single start node.
The name of the initial node is entered on the node. It takes the form of an adjective.
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A control flow connects any combination of: ◦ activities ◦ branches◦ merges◦ forks◦ joins
A control flow has direction, which is indicated by the arrow head – you may only traverse the control flow in the direction of the arrow.
A control flow may not enter an initial state. A control flow may not exit a final node. A control flow is the representation of an occurrence of an event. The name of the event is entered on the control flow. It takes the
form of something has been done, noun-verb(past-tense)
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The activity represents the actions that occur as a result of an incoming event from a control flow.
The name of the activity is entered on the activity and takes the form of something being done, present tense verb-noun
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The branch is used to show alternative paths in the activity diagram.
Label the decision node with a question(?). Do not label the merge, (unless you have a good
reason to). One control flow enters the decision node and two
or more alternative control flows exit the decision node.
Only one of the paths may be transitioned as the result of an event occurring.
Each exiting control flow contains the condition under which it is taken (called a guard), dependent upon the answer to the question. These guards must be mutually exclusive.
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The guards on exiting control flows must cover all possible outcomes of the question being asked by the branch.◦ The simplest way to ensure all possible outcomes are covered is
to phrase the branch question such that the only possible answers are ‘Yes’ or ‘No’. Note, this can add extra branches to the diagram.
Two or more control flows enter the merge node and one control flow exits.
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The fork may be represented by vertical or horizontal bars.
The fork represents that the flow through the diagram has split into 2 paths that are running in parallel (multitasking).
The fork has a single control flow on entry and several control flows exiting.
Use a fork when there is no requirement on the order of activities in a flow. ◦ For example, the Dematerializer receives an
event that the door is shut. It now suspends the cargo and creates a vacuum, but these actions may be performed in parallel, so we model them with a fork.
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For every fork there should be a join (if not your activity diagram is broken).
The join may be represented by vertical or horizontal bars.
A join simply shows that when the parallel activities have finished that they then come back to join a single flow again.
The join has several control flows entering and a single control flow on exit.
The exiting control flow cannot be executed until every incoming control flow has completed.
There is no need to label the fork or join.
The final node represents the termination of the activity diagram.
There may be several termination states in a single diagram.
Label the final node with an adjective.
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[Condition]
For each X:
START POINT
END POINT
STEP
TRANSITION
DECISION POINT
GUARD
REPEATED STEPS
PARALLEL STEPS
START POINT
The Start Point represents the EVENT that
triggers the use case.
END POINT
Actor elects to Add Customer
Actor elects to Add Customer
Label the End Point to EXPLICITLY confirm
that the intent of the use case has been achieved.
Actor elects to Add Customer
Customer added
Actor elects to Add Customer
Customer added
This makes it clear to the reader that the use case
is complete and that nothing further is needed
in order to fulfil the intent.
Actor elects to Add Customer
End of process
To reach the End Point…
… you need to model STEPS.
Link the steps with
TRANSITIONS.
Transitions use arrow heads to show the
direction of process flow.
I like to put a note against any step that achieves the goal of
the use case.
Goal X achieved
… because it might not be the last step.
Goal X achieved
Often in a use case the System has to make a decision
based on business rules...
The actual decision takes place within a
STEP
System determines
whether X or Y The actual decision takes place within a
STEP
System determines
whether X or Y A DECISION POINT is then used to help the reader navigate
the diagram.
DECISION POINT
Decision Points contain text which
describes the nature of the decision to be
made.
So was it X or Y?
Decision points allow the flow to branch
away from the Primary Path.
[Condition 2]
[Condition 1]
Transitions coming out of
Decision Points must have a
GUARD.
[IT WAS “Y”]
[IT WAS “X”]
A Guard needs to explicitly describe a
condition which must be true in order to proceed down that
path.
[Condition 2]
[Condition 1]
If the flow rejoins the
Primary Path, it is known as an Alternate Path.
[Condition 2][Condition 1]
You can show how paths rejoin by
using a MERGE POINT.
[Condition 2][Condition 1]
You can show how paths rejoin by
using a MERGE POINT.
[Condition 2][Condition 1]
I prefer to model merging paths like this.