Upload
manoj-reddy
View
475
Download
6
Embed Size (px)
DESCRIPTION
Unit 2(advanced class modeling & state diagram)
Citation preview
2
Example – Car
https://sites.google.com/a/cmrit.ac.in/manoj-c5559/
UNIT – 2: ADVANCED CLASS MODELING, STATE MODELING:
Advanced object and class concepts; Association ends; N-ary associations; Aggregation; Abstract classes; Multiple inheritance; Metadata; Reification; Constraints; Derived data; Packages; Practical tips.
State Modeling: Events, States, Transitions and Conditions; State diagrams; State diagram behaviour; Practical tips.
Advanced object and class concepts
Enumerations
Multiplicity
Scope
Visibility
Enumeration Data type - a set of values together with a set of operations on those
values
To define a new simple data type, called enumeration type, we need 2 things:
A name for the data type
A set of values for the data type
enum {FALSE, TRUE};enum rank {TWO, THREE, FOUR, FIVE, SIX, SEVEN, EIGHT,
NINE, TEN, JACK, QUEEN, KING, ACE};enum colors {BLACK, BLUE, GREEN, CYAN, RED};
The values are written in all caps because they are constants
EnumerationsWhen constructing a model, we should carefully note enumerations,
because they often occur and are important to users.
Enumerations are also significant for an implementation; we may display the possible values with a pick list.
Do not use a generalization to capture the values of an Enumerated attribute.
An Enumeration is merely a list of values; generalization is a means for structuring the description of objects.
Enumerations
In the UML an enumeration is a data type.
The second section lists the enumeration values.
Eg: Boolean type= { TRUE, FALSE}
ScopeScopeUML specifies two types of scope for members: instance and classifier.
Classifier members are commonly recognized as “static” in many programming languages. The scope is the class itself.Attribute values are equal for all instancesMethod invocation does not affect the instance’s state
Instance members are scoped to a specific instance.Attribute values may vary between instancesMethod invocation may affect the instance’s state (i.e., change
instance’s attributes)To indicate a classifier scope for a member, its name must be underlined.
Otherwise, instance scope is assumed by default.
11
Scope
Individual member data (attributes) may have either class scope or instance scope.
Class scope - A single copy of an attribute is shared by all instances of a class. In UML you underline the attribute to indicate class scope:
productCount : int
Instance scope - Each instance of a class would have its own copy of the attribute. All attributes have instance scope by default.
12
Scope examples
Visibility
Visibility refers to the ability of a method to reference a feature from another class and has the possible values of public, protected & private.
Public—Visible anywhere that the class in which it appears is visible; denoted by +.
Package—Visible anywhere in the package containing the class in which it appears; denoted by ~.
Protected—Visible in the class in which it appears and all its sub-classes; denoted by #.
Private—Visible only in the class in which it appears; denoted by -
Restricting visibility is the same as restricting accessibility.
VisibilityThe UML denotes visibility with a prefix
“+” public
“-” private
“#” protected
“~” package
15
Visibility Example
An n-ary association is like a common (binary) association, except that more than two association roles involved in it.
The UML symbol for n-ary associations is a diamond with lines connecting to related classes. If the association has a name, it is written in italics next to the diamond.
N-ary Association
Class1 Class2
Class3
N-aryassociation
Ternaryassociation
N-ary Associations
Associations can connect more than one classNotation:
Student Advisor
Major
N-ary Associations
datetrainNo
TraincarriageNo
seatNo
Seat
nametitle
Passenger
Reservation
1 1..*
1..*
N-ary Associations
We may occasionally encounter n-ary associations (association among 3 or more classes).
But we should try to avoid n-ary associations- most of them can be decomposed into binary associations, with possible qualifiers and attributes.
20
N-ary Association
21
N-ary Association (cont’d)
decompose
22
AggregationA special form of association that models a whole-part relationship between
an aggregate (the whole) and its parts.Models a “is a part-part of” relationship.
The aggregation association represents the part-whole relation between classes.Denoted by a solid diamond and linesDiamond attaches to the aggregate (whole) while lines attach to the partsMay have all association adornments
Whole Part
Car Door House
23
Aggregation (cont.)
Aggregation tests: Is the phrase “part of” used to describe the relationship?
A door is “part of” a carAre some operations on the whole automatically applied to its
parts? Move the car, move the door.
Are some attribute values propagated from the whole to all or some of its parts? The car is blue, therefore the door is blue. A door is part of a car. A car is not part of a door.
Car Door House
Whole Part
Aggregation
*Pizza Order
Slice
Crust
Sauce Serving
Cheese Serving
Topping Serving
25
CompositionComposition is a form of aggregation with strong
ownership and coincident lifetime of the parts by the whole; the part object may belong to only one whole – the parts are usually expected to live and die with the whole. (usually, any deletion of the whole is considered to cascade to the parts}{filled diamond}
Aggregation and Composition
Aggregation is a special form of association that specifies a whole-part relationship between the aggregate (the whole) and a component (the part); aggregation is the part-of relationship. { it is a special form of association in which a collection of objects, each having an independent existence, is associated with an single object} {unfilled diamond}
Composition is a form of aggregation with strong ownership and coincident lifetime of the parts by the whole; the part object may belong to only one whole – the parts are usually expected to live and die with the whole. (usually, any deletion of the whole is considered to cascade to the parts}{filled diamond}
Metadata
The term "meta" comes from a Greek word that denotes something of a higher or more fundamental nature. Metadata, then, is data about other data.
The term refers to any data used to aid the identification, description and location of networked electronic resources
Defining Metadata
Librarians equate it with a complete bibliographic record
Information technologists equate it to database schema or definitions of the data elements
Archivists include context information, restrictions and access terms, index terms, etc.
Metadata
Metadata is data that describes other data. For example, a class definition is a metadata.
Models are inherently metadata, since they describe the things being modeled (rather than being the things).
Many real-world applications have metadata, such as parts catalogs, blueprints, and dictionaries. Computer-languages implementations also use metadata heavily.
Derived Data
A derived element is a function of one or more elements, which in turn may be derived.
A derived element is redundant, because the other elements completely determine it.
Ultimately, the derivation tree terminates with base elements. Classes, associations, and attributes may be derived. The notation for a derived element is a slash in front of the element
name along with constraint that determines the derivation.
Derived Data
Employee
Basic Pay
/gross pay
Packages
A package is a group of elements (classes, association, generalization, and lesser packages) with a common theme.
A package partitions a model making it easier to understand and manage. Large applications my require several tiers of packages.
Packages form a tree with increasing abstraction toward the root, which is the application, the top-level package.
Notation for package is a box with a tab.
Customer Order
Sales
When to use Package
To create a overview of a large set of model elements
To organize a large model
To group related elements
State Modeling State model describes the sequences of operations that occur in
response to external stimuli.
The state model consists of multiple state diagrams, one for each class with temporal behavior that is important to an application.
The state diagram is a standard computer science concept that relates events and states.
Events represent external stimuli and states represent values objects.
Elements of State Diagrams
The basic elements of state diagrams are
Events – An event is an occurrence at a point in time
states – the state in which the object finds itself at any moment
transitions – take the object from one state to another
actions – take place as a result of a transition
EventsAn event is an occurrence at a point in time such as –
User presses left button
Indigo flight departs from Mumbai
An event happens instantaneously with regard to time scale of an application.
One event may logically precede or follow another, or the two events may be unrelated (concurrent; they have no effect on each other).
Types of Events
An event may be one of 3 types
Signal event
Time event
Change event
Signal EventA signal is an explicit one-way transmission of information from one
object to another.
An object sending a signal to another object may expect a reply, but the reply is a separate signal under the control of the second object, which may or may not choose to send it.
A signal event is the event of sending or receiving a signal (concern about receipt of a signal).
The difference between signal and signal eventa signal is a message between objects
a signal event is an occurrence in time.
Time EventTime event is an event caused by the occurrence of an absolute
time or the elapse of a time interval.UML notation for an absolute time is the keyword when
followed by a parenthesized expression involving time.The notation for a time interval is the keyword after followed
by a parenthesized expression that evaluates to a time duration.
when (date = jan 1, 2000 )
Change EventA change event occurs whenever a specified condition is met
Event name is specified as keyword whenParameter list is a Boolean expressionThe event occurs when both of the following conditions are met,
irrespective of the order when they happen The expression evaluates to true The object is in the required state
when (battery power < lower limit )
when (tire pressure < minimum pressure )
StatesState is a condition or situation during the life of an object within
which it performs some activity, or waits for some eventsThe objects in a class have a finite number of possible states.Each object can be in one state at a time.A state specifies the response of an object to input events. At any given point in time, the system is in one state.It will remain in this state until an event occurs that causes it to
change state.
Event vs. States Event represents points in time.State represents intervals of time.
States
A state is when a system is:
Doing something – e.g., heating oven, mixing ingredients, accelerating engine,
Waiting for something to happen – Waiting for user to enter password, waiting for sensor reading.
Eg:
power turned on power turned off power turned on
Time Powered
Not powered
A state corresponds to the interval between two events received by an object.
The state of an object depends on past events.
Basic UML Syntax
A state is drawn with a round box, with three compartments fornamestate variables (if any)actions to be performed
Name
state variables
actions
sometimesleft out whenempty
Transitions
A transition is a relationship between two states indicating that an object in the first state will enter the second state.
A transition is an instantaneous change from one state to another.
The transition is said to fire upon the change from the source state to target state.
A guard condition must be true in order for a transition to occur.
A guard condition is checked only once, at the time the event occurs, and the transition fires if the condition is true.
51
TransitionA directed relationship between two states.
Contains five parts
Source state - current state before transition fires. Event trigger - external stimulus that has the potential to
cause a transition to fire. Guard condition - a condition that must be satisfied before
a transition can fire. Target state - new state after transition fires.
Basic UML Syntax
A transition is drawn with an arrow, possibly labeled withevent causing the
transactionguard conditionAction to perform
AnEvent [guard] / SomeAction
53
Idle
Initial State
Running
Final State
State
Transition
53
Billing Example
State Diagrams show the sequences of states an object goes through during its life cycle in response to stimuli, together with its responses and actions; an abstraction of all possible behaviors.
Unpaid
Start End
PaidInvoice created paying Invoice destroying
AddParticipant / Set count = 0
cancel seminar
event action, taken duringtransition
Setup
do/initialize seminarAvailable
do/initialize seminar
Full
do/finalize seminar
[ count = 20 ]
guard
Canceled
do/refund payments
cancel seminar
multipleexits
cancelseminar
aktivity, carried outwhile in that state
Actions
Action
is an executable atomic computation
includes operation calls, the creation or destruction of another object, or the sending of a signal to an object
associated with transitions and during which an action is not interruptible -- e.g., entry, exit
Predefined Action Labels
“entry/” identifies an action, specified by the corresponding action expression,
which is performed upon entry to the state (entry action)“exit/”
identifies an action, specified by the corresponding action expression, that is performed upon exit from the state (exit action)
“do/” identifies an ongoing activity (“do activity”) that is performed as long as
the modeled element is in the state or until the computation specified by the action expression is completed (the latter may result in a completion event being generated).
“include/” is used to identify a submachine invocation. The action expression
contains the name of the submachine that is to be invoked.
State Diagrams notation
PaidUnpaidpaying
Invoice created
Invoice destroyed
name
state
final stateInitial state
transition
event
Here’s a simple example SD for a washing machine.
State
Transition
Condition
Action
60
A condition is typically some kind of event, e.g.:•Signal•Arrival of an object (data/material),•Etc…
Condition
Action
An action is the appropriate output or response to the event, e.g.:•Signal or message•Transfer of an object,•Calculation,•Etc…
State Diagrams (Traffic light example)
Yellow
Red
Green
Traffic LightState
Transition
Event
Start
Transitions
xx yyevent [guard] | action
The event that triggers the transition
Conditions that must be met for the transition to take place
The action that takes place when the transition is taken
Initial and Final States
An example:
At Work At Homego home
go to work
die die
64
State Diagrams
65
66
67
68
Phone Example
digit dialed (n)[incomplete]
Dialing Connecting
busy
connected
digit dialed (n)[valid] / connectdigit dialed (n)
[invalid]
Invalid
Ringing
Busy
68
69
States of Garment (Garments system)
Garment ordered
Material ordered
Material delivered
Marked out for cutting
Cut
Marked out for sewing
Sewn
Marked out for finishing
Finished
Deleted
71
State Diagrams
A state diagram describes the behaviour of a system, some part of a system, or an individual object.
At any given point in time, the system or object is in a certain state. Being in a state means that it is will behave in a specific way in
response to any events that occur.
Some events will cause the system to change state. In the new state, the system will behave in a different way to
events.
A state diagram is a directed graph where the nodes are states and the arcs are transitions.
72
Using Microsoft Visio
Visio can be used to draw UML diagrams It is component of Microsoft Office
73
Using Microsoft Visio (continued)
Available Sets of Shapes in the UML Collection
Activity Diagrams
Collaboration Diagrams
Components
Deployment Diagrams
Sequence Diagrams
State Diagrams (Statecharts)
Static Structures (shown) – include Packages and Classes
Use Case Diagrams
74
Using Microsoft Visio (concluded)
UML symbols can be displayed as icons with names or icons with descriptions
Both forms of display for the Use Case shape set are shown
Now, on to the demo!
75
start state
stop state
transition from one state to another
self-transition (no change of state)
event [guard] / action transition label (each of the three parts is optional)
state
The Inheritance Mechanism
Means of deriving new class from existing classes, called base classes
Reuses existing code eliminating tedious, error prone task of developing new code
Derived class developed from base by adding or altering code
Multiple Inheritance
A derived class with several base classes is known as multiple inheritance
Multiple inheritance permits a class to have more than one super class and to inherit features from all parents.
We can mix information from 2 or more sources.
This is a more complicated from of generalization than single inheritance.
The advantage of multiple inheritance is greater power in specifying classes and an increased opportunity for reuse.
The disadvantage is a loss of conceptual and implementation simplicity.
Credit Cards - Single Inheritance
Same basic features
Each is a little different
Voice Mail - Multiple Inheritance
Voice mail has featuresof both mail and phone
What Is A Constraint
A condition or restriction (a Boolean expression) expressed in natural language text or in a machine readable language for the purpose of declaring some of the semantics of an element
Some are predefined in UML (“xor”), others may be user-defined
OCL (Object Constraint Language) is a predefined language for writing constraints
81
Constraints
These are functional relation between entities of an object model.
Entity includes objects, classes, attributes, links and associations.
A constraint restricts the values that entities can assume.Simple constraints may be placed in object models and
complex may be in functional model.
82
Employee
salary
boss
{ salary < = boss.salary }
Window
Lengthwidth
{ 0.8 <= length / width < = 1.5 }
Constraints on objects