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ObjectObject--Oriented Software EngineeringOriented Software Engineering

Chapter 2

Unified ModelingLanguage

Object-Oriented Systems Development Bahrami © Irwin/ McGraw-Hill

Introduction• A model is an abstract representation

of a system, constructed to understand the system prior to building or modifying it.


building or modifying it. • Most of the modeling techniques

involve graphical languages.

Why Modeling?• Models make it easier to express complex

ideas. For example, an architectbuilds a model to communicate ideasmore easily to clients.


• Models reduce complexity by separatingthose aspects that are unimportant fromthose that are important.

Advantages of Modeling (Con’t)• Models enhance learning.• The cost of the modeling analysis is

much lower than the cost of similar experimentation conducted with a


experimentation conducted with a real system.

• Manipulation of the model (changing variables) is much easier than manipulating a real system.

Modeling Key Ideas

• A model is rarely correct on the first try.

• Always seek the advice and


• Always seek the advice and criticism of others.

• Avoid excess model revisions, as they can distort the essence of your model. Let simplicity and elegance guide you through the process.

The Unified Modeling Language (UML)

• The unified modeling language (UML) is alanguage for specifying, constructing,visualizing, and documenting the softwaresystem and its components.


A complete language for capturingknowledge (semantics) about asubject (system) andcommunicating the knowledge(syntax)

Primary goals in the design of the UML• Provide users a ready-to-use, expressive visual

modeling language to develop and exchangemeaningful models.

• Provide extensibility and specializationmechanisms to extend the core concepts.mechanisms to extend the core concepts.

• Be independent of particular programminglanguages and development processes.

• Provide a formal basis for understanding themodeling language.

• Encourage the growth of the OO tools market.• Support higher-level development concepts


History and Background

8

History of the UMLHistory of the UML

Nov ‘97 UML approved by the OMG

Creating UML

Static Views are modeled using Use Case Diagrams Class Diagrams Object Diagrams Component Diagrams Deployment Diagrams

What can you model with UML?


Deployment Diagrams

Dynamic Views are modeled usingSequence DiagramsCollaboration DiagramsActivity DiagramsState-chart Diagrams

Static Model• A static model can be viewed as a

"snapshot" of a system's parameters at rest or at a specific point in time.


point in time. • The classes’ structure

and their relationshipsto each other frozen in time are examples of static models.

Dynamic Model

• Is a collection of procedures orbehaviors that, taken together,reflect the behavior of a systemover time.


over time.• For example, an order interacts

with inventory to determineproduct availability.


Building Blocks of UMLTo understand the UML, you need to form a

conceptual model of the language, and thisrequires learning three basic building blocks:

1. Elements: Main “citizens” of the model2. Relationships: tie elements together3. Diagrams: mechanisms to group

interesting collections of elements andrelationships


Elements in UML

Structural Elements

1.Classes

Behavioral Elements

1. Interactions

Grouping Elements

Annotation Elements

1.Classes

2. Interfaces

3. Collaborations

4. Use cases

5. Active classes

6. Components

7. Node classes

1. Interactions

2. State Charts 1. Package 1. Note


Structural Elements

1.1. ClassClass:: It is a description of a set of objects

that share the same attributes,

Static part of the model to represent conceptual or physicalelements

“nouns” of the model

that share the same attributes,operations, relationships, andsemantics.

implements one or more interfaces. Graphically, a class is rendered as a

rectangle, usually including its name,attributes, and operations


Structural Elements

22.. InterfaceInterface::• is a collection of operations that

specify a service of a class orcomponent.

• An interface might represent thecomplete behavior of a class orcomponent or only a part of thatbehavior

• An interface rarely stands alone.


Agency

Structural Elements33.. ColloborationColloboration::• Defines an interaction between

elements• Several elements cooperating to

deliver a behavior rather thanindividual behavior

Capture online

individual behavior• Includes structural and behavioral

dimensions• Represents implementations of

patterns that make up a system


Structural Elements44.. UseUse CasesCases::• Description of a sequence of

actions that a system performs todeliver an observable result to aparticular actor

• Used to structure the behavioral• Used to structure the behavioralelements in a model

• Realized by collaboration• Graphically rendered as an

ellipse drawn with a solid line


Structural Elements55.. ActiveActive ClassesClasses::• A class whose objects own one or

more processes or threads andtherefore can initiate an action

• A class whose objects haveconcurrent behavior with otherconcurrent behavior with otherobjects

• Graphically, an active class isrendered just like a class drawnwith a thick line


Structural Elements6.6. ComponentComponent

• is a physical and replaceable part of a system that conforms to and provides the realization of a set of interfaces. interfaces.

• Graphically, a component is rendered as a rectangle with tabs

• it also can be used to represent applications, files, libraries,pagesand tables.

•


Structural Elements77.. NodeNode ClassClass::• is a physical element that exists at run

time • represents a computational resource,

generally having at least some memory and, often, processing capability. and, often, processing capability.

• a set of components may reside in a node• components may also migrate from one

node to another• Graphically, a node is rendered as a cube,

usually including only its name


Behavioral Elements

11.. InteractionInteraction::• a set of messages exchanged among a set of objects

within a particular context to accomplish a specific

These are the dynamic parts of UML models. Represent behavior over time and space“verbs” of the model

Save application()

within a particular context to accomplish a specific purpose

• specifies the behavior of a set of objects• involves a number of other elements:

– messages, action sequences (behavior invoked by a message) and links (connection between objects)

• graphically rendered as an arrow


Behavioral Elements22.. StateState MachineMachine::• specifies a sequence of states an object or an

interaction goes through during its lifetime and its response to external events

• may specify the behavior of an individual class or a collaboration of classescollaboration of classes

• includes a number of elements including states, transition, events and activities

• presented as a rounded rectangle with a name and sub-• states


Grouping Element

1.1. PackagePackage::• mechanism for organizing elements

into groups.

Are the organizational parts of UML models. These are the boxesinto which a model can be decomposed .There is one primarykind of grouping thing, namely, packages.

into groups.• All elements can be placed in a package.• Graphically, a package is rendered as a

tabbed folder, usually including only itsname and, sometimes, its contents


Annotational Element

1.1. NoteNote::• comments added to models for better

explanation or illumination on specific elements

are the explanatory parts of UML models. These are thecomments you may apply to describe about any element in amodel.

explanation or illumination on specific elements• explanatory aspect of UML models• notes are used primarily for annotation e.g. for

rendering constraints and comments attached to elements or collections of elements

• presented as a rectangle with a dog-eared corner• may include both textual and graphical comments


Relationships in the UML

1.1. DependencyDependency::

There are four kinds of relationships in the UML: 1. Dependency 2. Association 3. Generalization 4. Realization

1.1. DependencyDependency::• A semantic relationship between two

elements in which a change to oneelement (independent element) mayaffect the meaning of the other(dependent element)

• Given as a directed dashed line possiblywith a label


Relationships in the UML22.. AssociationAssociation::• a structural relationship describing a set of links• links are connections between objects• aggregation is a special type of association depicting

whole-part relationshipwhole-part relationship• association is presented as a solid line, possibly

directed, labeled and with adornments (multiplicityand role)


Relationships in the UML33.. GeneralizationGeneralization• a relationship in which objects of a

specialized element (child) are substitutable for objects of a generalized element (parent)

• child elements share the structure • child elements share the structure and behavior of the parent

• rendered graphically as a solid line with hollow arrow head pointing to the parent


Relationships in the UML44.. RealizationRealization::• a semantic relationship between

elements, wherein one element specifiesa contract and another guarantees tocarry out this contract

• relevant in two basic scenarios:• relevant in two basic scenarios:– interfaces versus realizing classes or

components– uses cases versus realizing collaborations

• graphically depicted as a dashed arrowwith hollow head a cross betweendependency and generalization


Diagrams in UML

• a graph presentation of a set of elements and relationships where:– nodes are elements– edges are relationships

• UML includes nine such diagrams

1. Class Diagram


Diagrams in UML1. Class Diagram: o Static structure of a

system

o Show a set of classes, interfaces, collaboration,


interfaces, collaboration, and their relationships

o address static design view of a system

Diagrams in UML2. Object Diagram: Static structure of a system at a particular time Show a set of objects and their relationshipsstatic snapshots of element instances found in class diagrams


Diagrams in UML3. Use Case Diagram: Functionality of a system Show a set of actors and use cases, and their relationshipsaddresses static use case view of the systemimportant for organizing and modeling the external behavior of the system


behavior of the system

Diagrams in UML4. Sequence Diagram: Interaction among elements of a system in a time sequence show interactions consisting of a set of objects and the messages sent and received by


objects and the messages sent and received by those objects address the dynamic behavior of a system with special emphasis on the chronological ordering of messages


Diagrams in UML5.Collaboration Diagram:

Interaction among elements and their relationsorganized in time and space

Show the structural organization of objects


Show the structural organization of objects that send and receive messages

Sequence and collaboration diagram are isomorphic i.e. one can be transformed into another


Diagrams in UML6. State Chart Diagram:

The status condition and responses of the elements ofa system

Show a state machine consisting of states, transitions,events, and activities


events, and activities address the dynamic view of a system important in modeling the behavior of an interface,

class or collaboration emphasize on event-driven ordering


Diagrams in UML7. Activity Diagram:

The activities of the system a diagram showing control/data flows from one

activity to another addresses the dynamic view of a system, useful for


addresses the dynamic view of a system, useful formodeling its functions

emphasizes the flow of control among objects


Diagrams in UML8.Component Diagram:

The organization of the elements realizing the systemShow the organization and dependencies amongst a

set of components address static implementation view of a system


address static implementation view of a system a component typically maps to one or more classes,

interfaces or collaborations


Diagrams in UML9.Deployment Diagram:

Configuration of environment elements and themapping of elements realizing the system into them



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