Introduction
The Unified Modeling Language or
simply UML is a standard language for specifying, visualizing, constructing,
and documenting the objects of software systems. So UML can be described as a
general purpose visual modeling language. Generally, it is used to model
software systems and it is also used to model non software systems that likely
process the flow in a manufacturing unit or software.
It
is different from the other common programming languages like C++, Java or
Visual Basic codes. More likely it is not a programming language but a tool
that can be used to generate code in various languages using UML diagrams. In
other words UML is a pictorial language used to make software blue prints. UML
has a direct relation with object oriented analysis and design ( Object-Oriented Analysis and Design with UML, Adegboyega Ojo, Elsa Estevez, October 2005).
Object
Oriented Analysis and Design
So what is an object oriented
analysis, it defined as investigation and to be more specific it is the
investigation of objects and the design means collaboration of identified
objects.
The
object oriented analysis can be described into three purposes namely first is identifying
the objects of a system, second is to identify their relationships and lastly
make a design which can be converted into an executable system. So the input from
the object oriented analysis and design is the input to the UML diagrams ( Object-Oriented Analysis and Design with UML, Adegboyega Ojo, Elsa Estevez, October 2005).
Buildings
Blocks
In Further notice the building
blocks for UML can be defined in their “Things”, “Relationships” and “Diagrams”
which produces the framework of the UML.
In
order to identify the images and objects of a diagram we should know the
important building blocks of UML namely the “Things”. It can be categorized as “Structural”,
“Behavioral”, “Grouping” and “Annotational” ( Design Patterns Application in UML, Gerson Suny e, Alain Le Guennec, and Jean-Marc J ez equel IRISA/CNRS, Campus de Beaulieu, F-35042 Rennes Cedex, FRANCE ).
Structural
Things
The Structural things define the
static part of a model. They represent the physical and conceptual elements. It
consists of class, interface, collaboration, use case, component and node. The
class represents set of objects having similar responsibilities. The interface defines
a set of operations which specify the responsibility of a class. The
collaboration defines interaction between elements. The use case represents a
set of actions performed by a system for a specific goal. The component
describes physical part of a system, and the node can be defined as a physical
element that exists at run time. For the
Behavioral things consist of dynamic parts of UML models. These include the interaction
that defines a behavior that consists of a group of messages exchanged among
elements to accomplish a specific task and the State machine defines the
sequence of states an object that goes through in response at certain events. The
events are external factors responsible for state change.The Grouping things
is a mechanism to group elements of a UML model together. The package is
the only one grouping thing available for gathering structural and behavioral
things. The last building block for UML is the Annotational things this capture
remarks, descriptions, and comments of UML model elements and its note is used
to render comments, constraints etc of an UML element (UML – a tutorial,Ian Graham or Alan Wills +44-161-225 3240; clive@trireme.com Copyright © MMI – Trireme International Ltd. ).
The Relationships which is a
building block shows how elements are associated with each other and this
association describes the functionality of an application. The four kinds of
relationships are dependency, association, generalization and realization. The Association
is a set of links that connects elements of a UML model. The Generalization
connects a specialized element with a generalized element and describes the relationship
in an object. The last is the Realization that describes two elements connected
in a relationship, the seperate elements in here describe the implemented
responsibility for every element they have in both ways (UML – a tutorial,Ian Graham or Alan Wills +44-161-225 3240; clive@trireme.com Copyright © MMI – Trireme International Ltd. ).
The over all elements that
combined all together produces the UML Diagrams and it provides the
representation of a complete system. The Unified Modeling Language includes
nine diagrams these are the Class diagram, Object diagram, Use Case diagram,
Sequence diagram, Collaboration diagram, Activity diagram, Statechart diagram,
Deployment diagram and Component diagram ( Object-Oriented Analysis
and Design with UML, Adegboyega Ojo, Elsa Estevez, October 2005).
UML
Diagrams
UML Class Diagram represents the
static view of an application. This is not only used for visualizing,
describing and documenting different aspects of a system it also includes the
construction of executable code for a software application. This may describe
the attributes and operations for a class and used in the modeling of object
oriented systems because it can map
directly with object oriented languages. It includes the classes, interfaces,
associations and collaborations and may also be said as a structural diagram.
Class
diagram is a graphical representation of the static view of a system and
represents different aspects of the application. In creating a class diagram
there are some notes to be remembered like in naming, it should be meaningful
to describe the aspect of the system. Each element and their relationships should
be identified in advance namely the attirbutes and methods, Each class should
tackle much less number of properties so that it wont get complicated and not
putting unneccesary properties. It should use notes to describe the aspect of
the diagram so it will be understandable for the developer or coder and lastly
the diagram should be drawn on plain paper and rework as many times as possible
to make it correct ( UML Tutorial: Part 1 -- Class Diagrams, Robert C. Martin ).
An example of this diagram is an
Order System of an application. It describes a particular aspect of the entire
application.
The Order and Customer are
identified as the two elements of the system and they have a one to many
relationship because a customer can have multiple orders.
We
would keep Order class to be an abstract class and it has two concrete classes
SpecialOrder and NormalOrder.
The
two classes have all the properties as the Order class. In addition they have
additional functions like dispatch and receive ( UML Tutorial: Part 1 -- Class Diagrams, Robert C. Martin ).
UML
Object Diagram
Object Diagram are dependent to
class diagram because it represent an instance of a class diagram and are used
to render a set of objects and their relationships as an instance and it is
unlimited. In Object diagram the elements are in concrete form to represent the
real world object.
The
Steps in creating a Object diagram is first is to analyze the system and decide
which instances are important data and association. Then consider only those
instances which will cover the functionality make some optimization as the
numbers of instances are unlimited. It should also consider the elements that
should be identified and the association among objects should be clarified.
Values of different
elements need to be captured to include in the object diagram and add proper
notes at points where more clarity is required (UML Process, Sharam Hekmat, PragSoft Corporation, www.pragsoft.com )
Example of
an order management system for UML Object Diagram
The following diagram is an
instance of the system at a particular time of purchase. It has the objects
namely Customer, Order, Special, Order and NormalOrder.
Now
the customer object (C) is associated with three order objects (O1, O2 and O3).
These order objects are associated with special order and normal order objects
(S1, S2 and N1). The customer is having the following three orders with
different numbers (12, 32 and 40) for the particular time considered.
Now the customer can increase
number of orders in future and in that scenario the object diagram will reflect
that. If order, special order and normal order objects are observed then we you
will find that they are having some values.
For orders the values are 12, 32,
and 40 which implies that the objects are having these values for the
particular moment (here the particular time when the purchase is made is
considered as the moment) when the instance is captured.
The same is for special order and
normal order objects which are having number of orders as 20, 30 and 60. If a
different time of purchase is considered then these values will change accordingly (UML Process, Sharam Hekmat, PragSoft Corporation, www.pragsoft.com ).
UML
Component Diagram
Component diagrams are used to
model physical aspects of a system. Physical aspects are the elements like
executables, libraries, files and documents.So component diagrams are used to
visualize the organization and relationships among components in a system.
These diagrams are also used to make executable systems.
For
creating a Component diagram the things to remember in particular is to
consider the files used in the system to be identified. Libraries and other
artifacts should be relevant to the application and relationships among the
artifacts should be I dentified clearly. Then work the use of meaningful name
to identify the component for which the diagram is to be drawn. Prepare a
mental layout before producing using tools and use notes for clarifying important
points (tutorialspoint.com)
A Component
diagram for an order management system
So the diagram shows the files in
the application and their relationships. In actual the component diagram also
contains dlls, libraries and folders.
In
the following diagram four files are identified and their relationships are
produced. Component diagram cannot be matched directly with other UML diagrams
in this blog. Because it is drawn for completely different purpose (tutorialspoint.com)
UML
Deployment Diagram
Deployment diagrams are used to
visualize the topology of the physical components of a system where the software
components are deployed and so as describing the hardware components where
software components are deployed. It also controls the “Performance”, “Scalability”,
“Maintainability” and “Portability”.
On
making a Deplpoyment diagram it better have to idebtify the relationship among
the nodes, the monitor, modem, caching server and the server.
An example
of a Deployment diagram below
The application is assumed to be a
web based application which is deployed in a clustered environment using server
1, server 2 and server 3. The user is connecting to the application using internet.
The control is flowing from the caching server to the clustered environment (tutorialspoint.com).
UML Use
Case Diagram
The Use Case diagram is dynamic
in nature and there should be some internal or external factors in making its
interaction. These internal and external agents are known as actors. So use
case diagrams are consists of actors, use cases and their relationships. The
diagram is used to model the system or subsystem of an application. A single
use case diagram captures a particular functionality of a system. The actors
can be human user, some internal applications or may be some external
applications.
For the creation of Use Case
diagram it should have the functionalities to be represented as a use case and relationships
among the use cases and actors and identified.
An example
of a Use Case representing the order management system
So if we look into the diagram
then we will find three use cases (Order, SpecialOrder and NormalOrder) and one
actor which is customer.
The
SpecialOrder and NormalOrder use cases are extended from Order use case. So
they have extends relationship. Another important point is to identify the
system boundary which is shown in the picture. The actor Customer lies outside
the system as it is an external user of the system (tutorialspoint.com).
UML
Interaction Diagram
The UML Interaction diagram is used
to describe some type of interactions among the different elements in the
model. So this interaction is a part of dynamic behaviour of the system.
This interactive behaviour is
represented in UML by two diagrams known as Sequence diagram and Collaboration
diagram. The basic purposes of both the diagrams are similar. Sequence diagram
emphasizes on time sequence of messages and collaboration diagram emphasizes on
the structural organization of the objects that send and receive messages. In drawing the Interaction diagram, there are
things to be identified likely the object organization then the objects taking part
in the interaction. The Message flows among the objects and the sequence in
which the messages are flowing.
The
Sequence Diagram
The sequence diagram is having
four objects (Customer, Order, SpecialOrder and NormalOrder). The diagram has
shown the message sequence for SpecialOrder object and the same can be used in
case of NormalOrder object. Now it is important to understand the time sequence
of message flows. The message flow is nothing but a method call of an object.
The first call is sendOrder which
is a method of Order object. The next call is confirm which is a method of
SpecialOrder object and the last call is Dispatch which is a method of
SpecialOrder object. So here the diagram is mainly describing the method calls
from one object to another and this is also the actual scenario when the system
is running (tutorialspoint.com).
The
Collaboration Diagram
It shows the object organization
as shown. Here in collaboration diagram the method call sequence is indicated
by some numbering technique as shown below. The number indicates how the
methods are called one after another. We have taken the same order management
system to describe the collaboration diagram.
The method calls are similar to
that of a sequence diagram. But the difference is that the sequence diagram
does not describe the object organization where as the collaboration diagram
shows the object organization.
Now to choose between these two
diagrams the main emphasis is given on the type of requirement. If the time
sequence is important then sequence diagram is used and if organization is
required then collaboration diagram is used (tutorialspoint.com).
UML
Statechart Diagram
UML Statechart diagram describes different
states of a component in a system. The states are specific to a component or
object of a system. A Statechart diagram describes a state machine. It can be
defined as a machine which defines different states of an object and these
states are controlled by external or internal events. As Statechart diagram
defines and states used to model lifetime of an object or simply describe the
states of different objects in its life cycle.
To clarify the Staechart diagram
it should identify the important objects to be analyzed its statesand identify
the events.
An example
of a Statechart diagram where the state of Order object is analyzed
The first state is an idle state
from where the process starts. The next states are arrived for events like send
request, confirm request, and dispatch order. These events are responsible for
state changes of order object.
During
the life cycle of an object (here order object) it goes through the following
states and there may be some abnormal exists also. This abnormal exit may occur
due to some problem in the system. When the entire life cycle is complete it is
considered as the complete transaction as mentioned in this diagram. The
initial and final state of an object is also shown here (tutorialspoint.com).
UML
Activity Diagram
Activity diagram is basically a
flow chart to represent the flow form one activity to another activity. The
activity can be described as an operation of the system. So the control flow is
drawn from one operation to another. This flow can be sequential, branched or
concurrent. Activity diagrams deals with all type of flow control by using different
elements. These additional capabilities include branching, parallel flow and
many other capabilties.
An example
of an Activity diagram for order management system
The main elements of the Activity
diagram here are to send order by the customer, receipt of the order, confirm
order, and dispatch order.
After
receiving the order request condition checks are performed to check if it is
normal or special order. After the type of order is identified dispatch
activity is performed and that is marked as the termination of the process.
This concluded the entire related
topic that considered in the Unified Modeling Language and hopefully discussed
in a proper manner. This is the whole discussion for this weekly blog in MIS (tutorialspoint.com).
References:
Object-Oriented Analysis
and Design with UML by Adegboyega Ojo
Elsa Estevez
Design Patterns
Application in UML by
Gerson Suny_e, Alain
Le Guennec, and Jean-Marc J_ez_equel
IRISA/CNRS,
Campus de Beaulieu, F-35042 Rennes Cedex, FRANCE
UML Process by Sharam
Hekmat PragSoft Corporation
www.pragsoft.com
UML - a tutorial , Ian Graham or Alan Wills +44-161-225 3240; clive@trireme.com
Copyright © MMI – Trireme International Ltd.
UML Tutorial: Part 1 -- Class Diagrams, Robert C. Martin
tutorialspoint.com
Eric Jeffrey Arriola
