UML-Advanced Software Engineering

UNIT-I
INTRODUCTION TO UML
Contents:
1. Importance of Modeling
2. Principles of Modeling
3. Object Oriented Modeling
4. Conceptual Model of the UML
5. Architecture
6. Software Development Life Cycle
1. Importance of Modeling:
Why do we model?
A model is a simplification at some level of abstraction
We build models to better understand the systems we are developing.
To help us visualize
To specify structure or behavior
To provide template for building system
To document decisions we have made
2. Principles of Modeling:
The models we choose have a profound influence on the solution we provide
Every model may be expressed at different levels of abstraction
The best models are connected to reality
No single model is sufficient, a set of models is needed to solve any nontrivial system
UML is a visual modeling language
“A picture is worth a thousand words.” - old saying
Unified Modeling Language:
“A language provides a vocabulary and the rules for combining words [...] for the purpose of
communication.

A modeling language is a language whose vocabulary and rules focus on the conceptual and
physical representation of a system. A modeling language such as the UML is thus a standard
language for software blueprints.”
Usages of UML:
UML is used in the course to
i. document designs
design patterns / frameworks
ii. represent different views/aspects of design – visualize and construct designs
static / dynamic / deployment / modular aspects
iii. provide a next-to-precise,common, language –specify visually
for the benefit of analysis, discussion, comprehension...
abstraction takes precedence over precision!
20/80 rule
aim is overview and comprehension; not execution
Object Oriented Modeling:
Traditionally two approaches to modeling a software system
Algorithmically – becomes hard to focus on as the requirements change
Object-oriented – models more closely real world entities

Conceptual Model of the UML:
Conceptual Model of UML
Building Blocks Rules Common Mechanisms
Things Relationships Diagrams 1) Specifications
2) Adornments
1. Class Diagram. 3) Common Divisions
1) Association 2. Object Diagram. 4) Extensibility Mechanisms
2) Dependency 3. Use Case Diagram.
3) Generalization 4. Sequence Diagram. *Stereotypes
4) Realization 5. Collaboration Diagram. *Tagged Values
6. State Chart Diagram. 1) Names *Constraints
7. Activity Diagram. 2) Scope
9. Deployment Diagram. 3) Visibility
4) Integrity
5) Execution
Structural Things Behavioral Things Grouping Things Annotational
Things
*Classes *Interaction *Packages *notes
*Interfaces *State machines
*Collaborations *States
*Use Case
*Component
*Node

To understand the UML, you need to form a conceptual model of the language, and this requires
learning three major elements: the UML's basic building blocks, the rules that dictate how those
building blocks may be put together, and some common mechanisms that apply throughout the
UML. Once you have grasped these ideas, you will be able to read UML models and create some
basic ones. As you gain more experience in applying the UML, you can build on this conceptual
model, using more advanced features of the language.
Building Blocks of the UML
The vocabulary of the UML encompasses three kinds of building blocks:
1. Things
2. Relationships
3. Diagrams
Things are the abstractions that are first-class citizens in a model; relationships tie these things
together; diagrams group interesting collections of things.
Things in the UML
There are four kinds of things in the UML:
1. Structural things
2. Behavioral things
3. Grouping things
4. Annotational things
These things are the basic object-oriented building blocks of the UML. You use them to write
well-formed models.
Structural Things
Structural things are the nouns of UML models. These are the mostly static parts of a model,
representing elements that are either conceptual or physical. Collectively, the structural things
are called classifiers.
A class is a description of a set of objects that share the same attributes, operations, relationships,
and semantics. A class implements one or more interfaces. Graphically, a class is rendered as a
rectangle, usually including its name, attributes, and operations, as in Figure 2-1.
Figure 2-1. Classes

An interface is a collection of operations that specify a service of a class or component. An
interface therefore describes the externally visible behavior of that element. An interface might
represent the complete behavior of a class or component or only a part of that behavior. An
interface defines a set of operation specifications (that is, their signatures) but never a set of
operation implementations. The declaration of an interface looks like a class with the keyword
«interface» above the name; attributes are not relevant, except sometimes to show constants. An
interface rarely stands alone, however. An interface provided by a class to the outside world is
shown as a small circle attached to the class box by a line. An interface required by a class from
some other class is shown as a small semicircle attached to the class box by a line, as in Figure 2-
2.
Figure 2-2. Interfaces
A collaboration defines an interaction and is a society of roles and other elements that work
together to provide some cooperative behavior that's bigger than the sum of all the elements.
Collaborations have structural, as well as behavioral, dimensions. A given class or object might
participate in several collaborations. These collaborations therefore represent the implementation
of patterns that make up a system. Graphically, a collaboration is rendered as an ellipse with
dashed lines, sometimes including only its name, as in Figure 2-3.

Figure 2-3. Collaborations
A use case is a description of sequences of actions that a system performs that yield observable
results of value to a particular actor. A use case is used to structure the behavioral things in a
model. A use case is realized by a collaboration. Graphically, a use case is rendered as an ellipse
with solid lines, usually including only its name, as in Figure 2-4.
Figure 2-4. Use Cases
The remaining three thingsactive classes, components, and nodesare all class-like, meaning they
also describe sets of entities that share the same attributes, operations, relationships, and
semantics. However, these three are different enough and are necessary for modeling certain
aspects of an object-oriented system, so they warrant special treatment.
An active class is a class whose objects own one or more processes or threads and therefore can
initiate control activity. An active class is just like a class except that its objects represent
elements whose behavior is concurrent with other elements. Graphically, an active class is
rendered as a class with double lines on the left and right; it usually includes its name, attributes,
and operations, as in Figure 2-5.
Figure 2-5. Active Classes

A component is a modular part of the system design that hides its implementation behind a set of
external interfaces. Within a system, components sharing the same interfaces can be substituted
while preserving the same logical behavior. The implementation of a component can be
expressed by wiring together parts and connectors; the parts can include smaller components.
Graphically, a component is rendered like a class with a special icon in the upper right corner, as
in Figure 2-6.
Figure 2-6. Components
The remaining two elementsartifacts and nodesare also different. They represent physical things,
whereas the previous five things represent conceptual or logical things.
An artifact is a physical and replaceable part of a system that contains physical information
("bits"). In a system, you'll encounter different kinds of deployment artifacts, such as source code
files, executables, and scripts. An artifact typically represents the physical packaging of source or
run-time information. Graphically, an artifact is rendered as a rectangle with the keyword
«artifact» above the name, as in Figure 2-7.
Figure 2-7. Artifacts

A node is a physical element that exists at run time and represents a computational resource,
generally having at least some memory and, often, processing capability. A set of components
may reside on a node and may also migrate from node to node. Graphically, a node is rendered
as a cube, usually including only its name, as in Figure 2-8.
Figure 2-8. Nodes
These elementsclasses, interfaces, collaborations, use cases, active classes, components, artifacts,
and nodesare the basic structural things that you may include in a UML model. There are also
variations on these, such as actors, signals, and utilities (kinds of classes); processes and threads
(kinds of active classes); and applications, documents, files, libraries, pages, and tables (kinds of
artifacts).
Behavioral Things
Behavioral things are the dynamic parts of UML models. These are the verbs of a model,
representing behavior over time and space. In all, there are three primary kinds of behavioral
things.
First, an interaction is a behavior that comprises a set of messages exchanged among a set of
objects or roles within a particular context to accomplish a specific purpose. The behavior of a
society of objects or of an individual operation may be specified with an interaction. An
interaction involves a number of other elements, including messages, actions, and connectors
(the connection between objects). Graphically, a message is rendered as a directed line, almost
always including the name of its operation, as in Figure 2-9.
Figure 2-9. Messages
Second, a state machine is a behavior that specifies the sequences of states an object or an

interaction goes through during its lifetime in response to events, together with its responses to
those events. The behavior of an individual class or a collaboration of classes may be specified
with a state machine. A state machine involves a number of other elements, including states,
transitions (the flow from state to state), events (things that trigger a transition), and activities
(the response to a transition). Graphically, a state is rendered as a rounded rectangle, usually
including its name and its substates, if any, as in Figure 2-10.
Figure 2-10. States
Third, an activity is a behavior that specifies the sequence of steps a computational process
performs. In an interaction, the focus is on the set of objects that interact. In a state machine, the
focus is on the life cycle of one object at a time. In an activity, the focus is on the flows among
steps without regard to which object performs each step. A step of an activity is called an action.
Graphically, an action is rendered as a rounded rectangle with a name indicating its purpose.
States and actions are distinguished by their different contexts.
Figure 2-11. Actions
These three elements interactions, state machines, and activities are the basic behavioral things
that you may include in a UML model. Semantically, these elements are usually connected to
various structural elements, primarily classes, collaborations, and objects.
Grouping Things
Grouping things are the organizational parts of UML models. These are the boxes into which a
model can be decomposed. There is one primary kind of grouping thing, namely, packages.
A package is a general-purpose mechanism for organizing the design itself, as opposed to
classes, which organize implementation constructs. Structural things, behavioral things, and even
other grouping things may be placed in a package. Unlike components (which exist at run time),
a package is purely conceptual (meaning that it exists only at development time). Graphically, a

package is rendered as a tabbed folder, usually including only its name and, sometimes, its
contents, as in Figure 2-12.
Figure 2-12. Packages
Packages are the basic grouping things with which you may organize a UML model. There are
also variations, such as frameworks, models, and subsystems (kinds of packages).
Annotational Things
Annotational things are the explanatory parts of UML models. These are the comments you may
apply to describe, illuminate, and remark about any element in a model. There is one primary
kind of annotational thing, called a note. A note is simply a symbol for rendering constraints and
comments attached to an element or a collection of elements. Graphically, a note is rendered as a
rectangle with a dog-eared corner, together with a textual or graphical comment, as in Figure 2-
13.
Figure 2-13. Notes
This element is the one basic annotational thing you may include in a UML model. You'll
typically use notes to adorn your diagrams with constraints or comments that are best expressed
in informal or formal text. There are also variations on this element, such as requirements (which
specify some desired behavior from the perspective of outside the model).
Relationships in the UML
There are four kinds of relationships in the UML:
1. Dependency

2. Association
3. Generalization
4. Realization
These relationships are the basic relational building blocks of the UML. You use them to write
well-formed models.
First, a dependency is a semantic relationship between two model elements in which a change to
one element (the independent one) may affect the semantics of the other element (the dependent
one). Graphically, a dependency is rendered as a dashed line, possibly directed, and occasionally
including a label, as in Figure 2-14.
Figure 2-14. Dependencies
Second, an association is a structural relationship among classes that describes a set of links, a
link being a connection among objects that are instances of the classes. Aggregation is a special
kind of association, representing a structural relationship between a whole and its parts.
Graphically, an association is rendered as a solid line, possibly directed, occasionally including a
label, and often containing other adornments, such as multiplicity and end names, as in Figure 2-
15.
Figure 2-15. Associations
Third, a generalization is a specialization/generalization relationship in which the specialized
element (the child) builds on the specification of the generalized element (the parent). The child
shares the structure and the behavior of the parent. Graphically, a generalization relationship is
rendered as a solid line with a hollow arrowhead pointing to the parent, as in Figure 2-16.
Figure 2-16. Generalizations

Fourth, a realization is a semantic relationship between classifiers, wherein one classifier
specifies a contract that another classifier guarantees to carry out. You'll encounter realization
relationships in two places: between interfaces and the classes or components that realize them,
and between use cases and the collaborations that realize them. Graphically, a realization
relationship is rendered as a cross between a generalization and a dependency relationship, as in
Figure 2-17.
Figure 2-17. Realizations
These four elements are the basic relational things you may include in a UML model. There are
also variations on these four, such as refinement, trace, include, and extend.
Diagrams in the UML
A diagram is the graphical presentation of a set of elements, most often rendered as a connected
graph of vertices (things) and paths (relationships). You draw diagrams to visualize a system
from different perspectives, so a diagram is a projection into a system. For all but the most trivial
systems, a diagram represents an elided view of the elements that make up a system. The same
element may appear in all diagrams, only a few diagrams (the most common case), or in no
diagrams at all (a very rare case). In theory, a diagram may contain any combination of things
and relationships. In practice, however, a small number of common combinations arise, which
are consistent with the five most useful views that comprise the architecture of a software-
intensive system. For this reason, the UML includes thirteen kinds of diagrams:
1. Class diagram
2. Object diagram
3. Component diagram
4. Composite structure diagram
5. Use case diagram
6. Sequence diagram
7. Communication diagram
8. State diagram
9. Activity diagram
10. Deployment diagram
11. Package diagram
12. Timing diagram
13. Interaction overview diagram
A class diagram shows a set of classes, interfaces, and collaborations and their relationships.

These diagrams are the most common diagram found in modeling object-oriented systems. Class
diagrams address the static design view of a system. Class diagrams that include active classes
address the static process view of a system. Component diagrams are variants of class diagrams.
An object diagram shows a set of objects and their relationships. Object diagrams represent
static snapshots of instances of the things found in class diagrams. These diagrams address the
static design view or static process view of a system as do class diagrams, but from the
perspective of real or prototypical cases.
A component diagram is shows an encapsulated class and its interfaces, ports, and internal
structure consisting of nested components and connectors. Component diagrams address the
static design implementation view of a system. They are important for building large systems
from smaller parts. (UML distinguishes a composite structure diagram, applicable to any class,
from a component diagram, but we combine the discussion because the distinction between a
component and a structured class is unnecessarily subtle.)
A use case diagram shows a set of use cases and actors (a special kind of class) and their
relationships. Use case diagrams address the static use case view of a system. These diagrams are
especially important in organizing and modeling the behaviors of a system.
Both sequence diagrams and communication diagrams are kinds of interaction diagrams. An
interaction diagram shows an interaction, consisting of a set of objects or roles, including the
messages that may be dispatched among them. Interaction diagrams address the dynamic view of
a system. A sequence diagram is an interaction diagram that emphasizes the time-ordering of
messages; a communication diagram is an interaction diagram that emphasizes the structural
organization of the objects or roles that send and receive messages. Sequence diagrams and
communication diagrams represent similar basic concepts, but each diagram emphasizes a
different view of the concepts. Sequence diagrams emphasize temporal ordering, and
communication diagrams emphasize the data structure through which messages flow. A timing
diagram (not covered in this book) shows the actual times at which messages are exchanged.
A state diagram shows a state machine, consisting of states, transitions, events, and activities. A
state diagrams shows the dynamic view of an object. They are especially important in modeling
the behavior of an interface, class, or collaboration and emphasize the event-ordered behavior of
an object, which is especially useful in modeling reactive systems

An activity diagram shows the structure of a process or other computation as the flow of control
and data from step to step within the computation. Activity diagrams address the dynamic view
of a system. They are especially important in modeling the function of a system and emphasize
the flow of control among objects.
A deployment diagram shows the configuration of run-time processing nodes and the
components that live on them. Deployment diagrams address the static deployment view of an
architecture. A node typically hosts one or more artifacts.
An artifact diagram shows the physical constituents of a system on the computer. Artifacts
include files, databases, and similar physical collections of bits. Artifacts are often used in
conjunction with deployment diagrams. Artifacts also show the classes and components that they
implement. (UML treats artifact diagrams as a variety of deployment diagram, but we discuss
them separately.)
A package diagram shows the decomposition of the model itself into organization units and their
dependencies.
A timing diagram is an interaction diagram that shows actual times across different objects or
roles, as opposed to just relative sequences of messages. An interaction overview diagram is a
hybrid of an activity diagram and a sequence diagram. These diagrams have specialized uses and
so are not discussed in this book. See the UML Reference Manual for more details.
This is not a closed list of diagrams. Tools may use the UML to provide other kinds of diagrams,
although these are the most common ones that you will encounter in practice.
Rules of the UML
The UML's building blocks can't simply be thrown together in a random fashion. Like any
language, the UML has a number of rules that specify what a well-formed model should look
like. A well-formed model is one that is semantically self-consistent and in harmony with all its
related models.
The UML has syntactic and semantic rules for
Names What you can call things, relationships, and diagrams

Scope The context that gives specific meaning to a name
Visibility How those names can be seen and used by others
Integrity How things properly and consistently relate to one another
Execution What it means to run or simulate a dynamic model
Models built during the development of a software-intensive system tend to evolve and may be
viewed by many stakeholders in different ways and at different times. For this reason, it is
common for the development team to not only build models that are well-formed, but also to
build models that are
Elided Certain elements are hidden to simplify the view
Incomplete Certain elements may be missing
Inconsistent The integrity of the model is not guaranteed
These less-than-well-formed models are unavoidable as the details of a system unfold and churn
during the software development life cycle. The rules of the UML encourage youbut do not force
youto address the most important analysis, design, and implementation questions that push such
models to become well-formed over time.
Common Mechanisms in the UML
A building is made simpler and more harmonious by the conformance to a pattern of common
features. A house may be built in the Victorian or French country style largely by using certain
architectural patterns that define those styles. The same is true of the UML. It is made simpler by
the presence of four common mechanisms that apply consistently throughout the language.
1. Specifications
2. Adornments
3. Common divisions
4. Extensibility mechanisms
Specifications
The UML is more than just a graphical language. Rather, behind every part of its graphical
notation there is a specification that provides a textual statement of the syntax and semantics of
that building block. For example, behind a class icon is a specification that provides the full set
of attributes, operations (including their full signatures), and behaviors that the class embodies;
visually, that class icon might only show a small part of this specification. Furthermore, there
might be another view of that class that presents a completely different set of parts yet is still
consistent with the class's underlying specification. You use the UML's graphical notation to

visualize a system; you use the UML's specification to state the system's details. Given this split,
it's possible to build up a model incrementally by drawing diagrams and then adding semantics to
the model's specifications, or directly by creating a specification, perhaps by reverse engineering
an existing system, and then creating diagrams that are projections into those specifications.
The UML's specifications provide a semantic backplane that contains all the parts of all the
models of a system, each part related to one another in a consistent fashion. The UML's diagrams
are thus simply visual projections into that backplane, each diagram revealing a specific
interesting aspect of the system.
Adornments
Most elements in the UML have a unique and direct graphical notation that provides a visual
representation of the most important aspects of the element. For example, the notation for a class
is intentionally designed to be easy to draw, because classes are the most common element found
in modeling object-oriented systems. The class notation also exposes the most important aspects
of a class, namely its name, attributes, and operations.
A class's specification may include other details, such as whether it is abstract or the visibility of
its attributes and operations. Many of these details can be rendered as graphical or textual
adornments to the class's basic rectangular notation. For example, Figure 2-18 shows a class,
adorned to indicate that it is an abstract class with two public, one protected, and one private
operation.
Figure 2-18. Adornments
Every element in the UML's notation starts with a basic symbol, to which can be added a variety
of adornments specific to that symbol.
Common Divisions
In modeling object-oriented systems, the world often gets divided in several ways.
First, there is the division of class and object. A class is an abstraction; an object is one concrete

manifestation of that abstraction. In the UML, you can model classes as well as objects, as
shown in Figure 2-19. Graphically, the UML distinguishes an object by using the same symbol
as its class and then simply underlying the object's name.
Figure 2-19. Classes and Objects
In this figure, there is one class, named Customer, together with three objects: Jan (which is
marked explicitly as being a Customer object), :Customer (an anonymous Customer object),
and Elyse (which in its specification is marked as being a kind of Customer object, although it's
not shown explicitly here).
Almost every building block in the UML has this same kind of class/object dichotomy. For
example, you can have use cases and use case executions, components and component instances,
nodes and node instances, and so on.
Second, there is the separation of interface and implementation. An interface declares a contract,
and an implementation represents one concrete realization of that contract, responsible for
faithfully carrying out the interface's complete semantics. In the UML, you can model both
interfaces and their implementations, as shown in Figure 2-20.
Figure 2-20. Interfaces and Implementations
In this figure, there is one component named SpellingWizard.dll that provides (implements)
two interfaces, IUnknown and ISpelling. It also requires an interface, IDictionary, that must
be provided by another component.

Almost every building block in the UML has this same kind of interface/implementation
dichotomy. For example, you can have use cases and the collaborations that realize them, as well
as operations and the methods that implement them.
Third, there is the separation of type and role. The type declares the class of an entity, such as an
object, an attribute, or a parameter. A role describes the meaning of an entity within its context,
such as a class, component, or collaboration. Any entity that forms part of the structure of
another entity, such as an attribute, has both characteristics: It derives some of its meaning from
its inherent type and some of its meaning from its role within its context (Figure 2-21).
Figure 2-21. Part with role and type
Extensibility Mechanisms
The UML provides a standard language for writing software blueprints, but it is not possible for
one closed language to ever be sufficient to express all possible nuances of all models across all
domains across all time. For this reason, the UML is opened-ended, making it possible for you to
extend the language in controlled ways. The UML's extensibility mechanisms include
Stereotypes
Tagged values
Constraints
A stereotype extends the vocabulary of the UML, allowing you to create new kinds of building
blocks that are derived from existing ones but that are specific to your problem. For example, if
you are working in a programming language, such as Java or C++, you will often want to model
exceptions. In these languages, exceptions are just classes, although they are treated in very
special ways. Typically, you only want to allow them to be thrown and caught, nothing else. You
can make exceptions first-class citizens in your modelsmeaning that they are treated like basic
building blocksby marking them with an appropriate stereotype, as for the class Overflow in
Figure 2-19.
A tagged value extends the properties of a UML stereotype, allowing you to create new
information in the stereotype's specification. For example, if you are working on a shrink-

wrapped product that undergoes many releases over time, you often want to track the version and
author of certain critical abstractions. Version and author are not primitive UML concepts. They
can be added to any building block, such as a class, by introducing new tagged values to that
building block. In Figure 2-19, for example, the class EventQueue is extended by marking its
version and author explicitly.
A constraint extends the semantics of a UML building block, allowing you to add new rules or
modify existing ones. For example, you might want to constrain the EventQueue class so that all
additions are done in order. As Figure 2-22 shows, you can add a constraint that explicitly marks
these for the operation add.
Figure 2-22. Extensibility Mechanisms
Collectively, these three extensibility mechanisms allow you to shape and grow the UML to your
project's needs. These mechanisms also let the UML adapt to new software technology, such as
the likely emergence of more powerful distributed programming languages. You can add new
building blocks, modify the specification of existing ones, and even change their semantics.
Naturally, it's important that you do so in controlled ways so that through these extensions, you
remain true to the UML's purpose the communication of information.
Architecture:
Any real world system is used by different users. The users can be developers, testers, business
people, analysts and many more. So before designing a system the architecture is made with
different perspectives in mind. The most important part is to visualize the system from different
viewer.s perspective. The better we understand the better we make the system.
UML plays an important role in defining different perspectives of a system. These perspectives
are:
Design View
Implementation View
Process View
Deployment View
Usecase View

And the centre is the Use Case view which connects all these four. A Use case represents the
functionality of the system. So the other perspectives are connected with use case.
Design of a system consists of classes, interfaces and collaboration. UML provides class
diagram, object diagram to support this.
Implementation defines the components assembled together to make a complete
physical system. UML component diagram is used to support implementation
perspective.
Process defines the flow of the system. So the same elements as used in Design are also
used to support this perspective.
Deployment represents the physical nodes of the system that forms the hardware. UML
deployment diagram is used to support this perspective.
Software Development Life Cycle:
The Unified Software Development Process
A software development process is the set of activities needed to transform a user„s
requirements into a software system.
Basic properties:
• use case driven
• architecture centric
• iterative and incremental
Use case Driven
Use cases
• capture requirements of the user,
• divide the development project into smaller subprojects,
• are constantly refined during the whole development process
• are used to verify the correctness of the implemented software
Architecture Centric:
• Find structures which are suitable to achive the function specified in the use cases,
• understandable,
• maintainable,
• reusable for later extensions or newly discovered use cases and describe them, so that they can
be communicated between developers and users.
Inception establishes the business rationale for the project and decides on the scope
of the project.

Elaboration is the phase where you collect more detailed requirements, do high-level analysis
and design to establish a baseline architecture and create the plan for construction.
Construction is an iterative and incremental process. Each iteration in this phase builds
production- quality software prototypes , tested and integrated as subset of the requirements of
the project.
Transition contains beta testing , performance tuning and user training.

UML-Advanced Software Engineering

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