traditional approach vs oo approach
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SYSTEM ANALYSIS & DESIGN (MTD 2033)
1
Function
Two Approaches to System Development
1. Traditional Approach
2. Object – oriented Approach
The Traditional Approach
Introduction
Traditional Approach includes many variations based on techniques used to develop information
system with structured and modular programming
Traditional Approach also known as Structured System Development
Structured analysis and design technique (SADT)
Structured approach which as known as Structured analysis and design technique (SADT)
SADT is a software engineering methodology for describing systems as a hierarchy of functions.
SADT is a graphical language that for describing systems , together with a methodology for
producing such as description
SADT basis element :
Diagrammatic notation designed specifically to help people describe and understand systems
Offers building blocks (boxes) to represent entities and activities
Offers variety of arrows to relate boxes
Boxes and arrows have an associated (informal) semantics; users are aided by boxes and arrow
labels, other informal documentation.
There are 3 techniques in SADT :
i. Structured programming
Structured programming is based on the theory that modularization makes for better
programs.
Controls
Inputs Outputs
Mechanisms
SYSTEM ANALYSIS & DESIGN (MTD 2033)
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High quality programs not only produce the correct outputs each time program runs ,
they make it easy for other programmers to read and modify the program later and
programs need to be modified all the time
A structured program is one that has one beginning and one ending and each step of
three programming constructs :
- A sequence of program statements
- A decision where one set of statements or another set of statement
executes
Stand Up
Walk To the Window
Turn Right
Look outside
Take an umbrella
Wear sunscreen Is it raining?
Yes
No
SYSTEM ANALYSIS & DESIGN (MTD 2033)
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- A repetition of a set of statement
Another concept that related to structured programming is top down programming.
Top down programming divides more complex programs into a hierarchy of program
modules (paragraph or procedure) using the rules of structured programming (one
beginning , one end , and sequence , decision and repetition constructs)
Top down programming also known as modular programming
One program calls other programs to work together as single system
Practicing top-down programming has several advantages:
Separating the low level work from the higher level abstractions leads to a
modular design.
Modular design means development can be self contained.
Having "skeleton" code illustrates clearly how low level modules integrate.
Fewer operations errors (to reduce errors, because each module has to be
processed separately, so programmers get large amount of time for processing).
Much less time consuming (each programmer is only involved in a part of the
big project).
Very optimized way of processing (each programmer has to apply their own
knowledge and experience to their parts (modules), so the project will become
an optimized one).
Easy to maintain (if an error occurs in the output, it is easy to identify the errors
generated from which module of the entire program).
Some modules will be standard procedures used again and again in different
programs or parts of the same program; for example, a routine to display a
standard opening screen.
Take a step
Are you at your destination?
Stop
No
Yes
SYSTEM ANALYSIS & DESIGN (MTD 2033)
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A module is small enough o be understandable as a unit of code. It is therefore
easier to understand and debug, especially if its purpose is clearly defined and
documented.
Program maintenance becomes easier because the affected modules can be
quickly identified and changed.
In a very large project, several programmers may be working on a single
program. Using a modular approach, each programmer can be given a specific
set of modules to work on. This enables the whole program to be finished
sooner.
More experienced programmers can be given the more complex modules to
write, and the junior programmers can work on the simpler modules.
Modules can be tested independently, thereby shortening the time taken to get
the whole program working.
If a programmer leaves part way through a project, it is easier for someone else
to take over a set of self contained modules.
A large project becomes easier to monitor and control.
- Top programming or modular programming
ii. Structured design (SD)
Methods for analyzing and converting business requirements into specifications and
ultimately, computer programs, hardware configurations and related manual
procedures
SYSTEM ANALYSIS & DESIGN (MTD 2033)
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A techniques providing guidelines for deciding what the set of programs should be ,
what each program should accomplish and how the programs should be organized into
a hierarchy
Structured Design views the word as a collection of modules with functions, that share
data with other (sub) modules. Example: structure chart
Structured Design addresses the synthesis of a module hierarchy.
The principles of cohesion and coupling are applied to derive an optimal module
structure and interfaces.
Cohesion is concerned with the grouping of functionally related processes into a
particular module.
Coupling addresses the flow of information, or parameters, passed between modules.
Optimal coupling reduces the interfaces of modules, and the resulting complexity of the
software.
The structure chart shows the module hierarchy or calling sequence relationship of
modules. There is a module specification for each module shown on the structure chart.
The module specifications can be composed of pseudo-code or a program design
language. The data dictionary is like that of structured analysis. At this stage in the
software development lifecycle, after analysis and design have been performed, it is
possible to automatically generate data type declarations, and procedure or subroutine
templates.
SYSTEM ANALYSIS & DESIGN (MTD 2033)
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iii. Structured analysis (SA)
A technique use to define what processing the system needs to do, what data it needs
to store and used, and what inputs and outputs are needed (External approach : events
and reactions to event) (Internal approach : functions , inputs , outputs)
In structured analysis there are three orthogonal views:
The functional view, made up of data flow diagrams, is the primary view of the
system. It defines what is done, the flow of data between things that are done
and provides the primary structure of the solution. Changes in functionality
result in changes in the software structure.
The data view, made up of entity relationship diagrams, is a record of what is in
the system, or what is outside the system that is being monitored. It is the static
structural view.
The dynamic view, made up of state transition diagrams, defines when things
happen and the conditions under which they happen.
The result of structured analysis is a set of related graphical diagrams, process
descriptions, and data definitions.
Approach for structured analysis consists of the following objects :
Data Flow Diagrams (DFD)
–Shows processes and flow of data in and out of
these processes.
–Does not show control structures (loops)
–Contains 5 graphic symbols (shown later)
–Uses layers to decompose complex systems (show later)
–Can be used to show logical and physical
–Were a quantum leap forward to other techniques at the time, I.e. monolithic
descriptions with globs of text
–Still used today to document business and/or other processes.
SYSTEM ANALYSIS & DESIGN (MTD 2033)
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Context Diagram
-Represent all external entities that may interact with a system
-This diagram pictures the system at the center, with no details of its interior
structure, surrounding by all its interacting systems, environment and activities.
- The objective of a system context diagram is to focus attention on external
factors and events that should be considered in developing a complete set of
system requirements and constrains.
- System context diagram are related to Data Flow Diagram
- Context diagrams can be helpful in understanding the context in which the
system will be part of software engineering
Data Dictionary
- A data dictionary or database dictionary is a file that defines the basic
organization of a database.
- A database dictionary contains a list of all files in the database, the number of
records in each file, and the names and types of each data field
-Most database management systems keep the data dictionary hidden from
users to prevent them from accidentally destroying its contents
-Data dictionaries do not contain any actual data from the database, only
bookkeeping information for managing it. Without a data dictionary, however, a
database management system cannot access data from the database
SYSTEM ANALYSIS & DESIGN (MTD 2033)
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Object – Oriented Approach
Introduction
An approach to system development that views information system as a collection of interacting
objects that work together to accomplish task
The OO approach is a different way of developing software.
Object is a things in computer system that can respond to messages
Object oriented notions :
-Class: metadata, i.e. definition of data structures, methods by which they can be operated and
behavior of class entities (i.e. interface with entities)
-Object: instances of class, i.e. contains an actual data, code, input and output;
-Object has observable behavior: can process data, send and respond to messages
-Information system is collection of interacting objects that work together to accomplish tasks
-Main concepts: instantiation and inheritance
Conceptually , no process , programs , data entities or files are defined – just objects
OO languages includes C++ , Java and C# , all these languages focus on writing definitions of the
types of object needed in a system , as a result all parts of a system can be thought as objects ,
not just GUI.
Object-Oriented
Three approach of object oriented are :
i. Object-oriented analysis (OOA)
Defining all the types of objects that do the work in the system and showing what use
cases are required to complete tasks
OOA applies object-modeling techniques to analyze the functional requirements for a
system
Looks at the problem domain, with the aim of producing a conceptual model of the
information that exists in the area being analyzed.
Analysis models do not consider any implementation constraints that might exist, such
as concurrency, distribution, persistence, or how the system is to be built.
The sources for the analysis can be a written requirements statement, a formal vision
document, and interviews with stakeholders or other interested parties.
A system may be divided into multiple domains, representing different business,
technological, or other areas of interest, each of which are analyzed separately.
The result of object-oriented analysis is a description of what the system is functionally
required to do, in the form of a conceptual model.
That will typically be presented :
SYSTEM ANALYSIS & DESIGN (MTD 2033)
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i. a set of use cases
- A use case in software engineering and systems engineering is a description of a
system’s behavior as it responds to a request that originates from outside of that
system. In other words, a use case describes "who" can do "what" with the system
in question. The use case technique is used to capture a system's behavioral
requirements by detailing scenario-driven threads through the functional
requirements.
ii. one or more UML class diagrams
- Unified Modeling Language (UML) is a standardized general-purpose modeling
language in the field of software engineering. UML includes a set of graphical
notation techniques to create visual models of software-intensive systems
iii. a number of interaction diagrams.
-Interaction diagrams, a subset of behavior diagrams, emphasize the flow of
control and data among the things in the system being modeled:
Communication diagram: shows the interactions between objects or
parts in terms of sequenced messages. They represent a combination of
information taken from Class, Sequence, and Use Case Diagrams
describing both the static structure and dynamic behavior of a system
SYSTEM ANALYSIS & DESIGN (MTD 2033)
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Interaction overview diagram: are types of activity diagram in which the
nodes represent interaction diagrams.
Sequence diagram: shows how objects communicate with each other in
terms of a sequence of messages. Also indicates the lifespan of objects
relative to those messages.
Timing diagrams: are specific types of interaction diagram, where the
focus is on timing constraints.
SYSTEM ANALYSIS & DESIGN (MTD 2033)
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It may also include some kind of user interface mock-up. object oriented analysis is to
develops a model that describe computer software as it works to satisfy a set of
customer define requirements’
ii. Object-oriented design (OOD)
Defining all of the types of object necessary to communicate with people and devices in
the system , showing how objects interact to complete tasks and refining the definitions
of each type of object so it can be implemented with specific language or environment
Object-oriented design is the process of planning a system of interacting objects for the
purpose of solving a software problem.
The input for object-oriented design is provided by the output of object-oriented
analysis.
Realize that an output artifact does not need to be completely developed to serve as
input of object-oriented design; analysis and design may occur in parallel, and in
practice the results of one activity can feed the other in a short feedback cycle through
an iterative process.
Both analysis and design can be performed incrementally, and the artifacts can be
continuously grown instead of completely developed in one shot.
Some typical input artifacts for object-oriented design are:
Conceptual model
Use case
System Sequence Diagram.
User interface documentations
Relational data model
Class diagrams derived from conceptual diagram and use cases
Class diagrams a graphical model used in the object-oriented approach to show classes
of objects in the system
Elements of class diagrams are:
Classes, metadata describing association of data structures with the
methods or functions that act on the data
Links describe relationship between classes
Types of links: Association, aggregation, composition
Classes relate in class relationship that can be inheritance ,dependency,
subtype ,supertype
Class diagrams derived from conceptual diagram and use cases
SYSTEM ANALYSIS & DESIGN (MTD 2033)
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iii. Object-oriented programming
Writing statements in a programming language to define what each type of object does,
including the messages that the objects send to each other
Object-oriented programming (OOP) is a programming paradigm that uses "objects" –
data structures consisting of data fields and methods – and their interactions to design
applications and computer programs
The five basic concepts of object-oriented design are the implementation level features
that are built into the programming language. These features are often referred to by
these common names:
Object/Class: A tight coupling or association of data structures with the
methods or functions that act on the data. This is called a class, or
object (an object is created based on a class). Each object serves a
separate function. It is defined by its properties, what it is and what it
can do. An object can be part of a class, which is a set of objects that are
similar.
Information hiding: The ability to protect some components of the
object from external entities. This is realized by language keywords to
enable a variable to be declared as private or protected to the owning
class.
Inheritance: The ability for a class to extend or override functionality of
another class. The so-called subclass has a whole section that is the
superclass and then it has its own set of functions and data.
Interface: The ability to defer the implementation of a method. The
ability to define the functions or methods signatures without
implementing them.
Polymorphism: The ability to replace an object with its subobjects. The
ability of an object-variable to contain, not only that object, but also all
of its subobjects.
SYSTEM ANALYSIS & DESIGN (MTD 2033)
Traditional Approach VS Object Oriented Approach
Categories Traditional Approach Object Oriented Approach
Overview Computer systems viewed as a collection of
computer programs
Includes many variations based on
techniques used to develop information
system with structured and modular
programming
Similar things can be grouped and classified.
Same goes for related things.
Analysis A technique use to define what processing
the system needs to do, what data it needs to
store and used, and what inputs and outputs
are needed
Defining all the types of objects that do the
work in the system and showing what use
cases are required to complete tasks
Analysis tools Data Flow Diagrams (DFD)
Context Diagram
Data Dictionary
a set of use cases
one or more UML class diagrams
a number of interaction diagrams
(Communication diagram , Interaction
overview diagram , Sequence diagram ,
Timing diagrams)
Programming One that has one beginning and one ending
and each step of three programming
constructs
Writing statements in a programming
language to define what each type of object
does, including the messages that the objects
send to each other
Programming construct sequence of set of instructions Object/Class
SYSTEM ANALYSIS & DESIGN (MTD 2033)
choice on set of instructions
Repetition of a set of instructions
Top programming or modular programming
Information hiding
Inheritance
Interface
Polymorphism
Design Methods for analyzing and converting
business requirements into specifications and
ultimately, computer programs, hardware
configurations and related manual
procedures
Defining all of the types of object necessary
to communicate with people and devices in
the system , showing how objects interact to
complete tasks and refining the definitions of
each type of object so it can be implemented
with specific language or environment
Design technique Structured Design Conceptual model
Use case
System Sequence Diagram
User interface documentations
Relational data model Similarity identifies business events
defines users’ requirements
data modeling concepts & techniques
user interfaces
Benefits Easy to maintain (if an error occurs in the
output, it is easy to identify the errors
generated from which module of the entire
program)
DFDs have become a popular tool for
business process redesign.
Very optimized way of processing (each
programmer has to apply their own
Increase in productivity has not kept pace
with increased demand for speedy delivery of
new software.
Existing software needs massive maintenance
effort to keep them operational.
Some companies spend up to 80% of IT
resources for maintenance.
Customers get better systems at less cost.
Projects are done on time.
SYSTEM ANALYSIS & DESIGN (MTD 2033)
knowledge and experience to their parts
(modules), so the project will become an
optimized one).
Provides clear-cut steps from the beginning
to the end of SLDC
Systems organizations and companies
become more competitive.
Maintenance for these systems is lower.
Changes can be made to systems faster and
with less cost
Disadvantages Estimating time and costs is difficult for each stage.
Never backward (Traditional) Little room for iteration Difficulty responding to changes
Benefits are not easily attainable.
Even with OO technology, it is still possible to
design a truly awful system in terms of
quality and maintainability.
OO technology and development methods
are still not mature or stable. OO is still
relatively new.
Any large-scale change to new technology
and methods is likely to be time consuming.
Substantial learning curve. Productivity and
quality decreases as staff are learning new
methodology.
Some benefits will show up only after a
considerable amount of time.
Benefits from reuse are only achievable after
a certain portfolio of system components has
been developed
SYSTEM ANALYSIS & DESIGN (MTD 2033)
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Reference
Levitt, D. (2000). Introduction to Structured Analysis and Design
Retrieved Sept 11, 2009, from
http://faculty.inverhills.edu/dlevitt/CS%202000%20%28FP%29/Introduction%20to%20Structured%2
0Analysis%20and%20Design.pdf
Mohammad.R (2004). Issues of Structure VS Object–Oriented Methodology Of Systems and Design
(Volume V,No 1) Retrieved from University Houstan-Clear Lake
from http://www.iacis.org/iis/2004_iis/PDFfiles/Rob.pdf
Mylopoulos J. (2000). Structured Analysis and Design Technique (SADT)
Retrieved Sept 11, 2009, from http://www.cs.toronto.edu/~jm/2507S/Notes04/SADT.pdf
Object-oriented Analysis and Design. (2009). Wikipedia, the free encyclopedia.
Retrieved Sept 11, 2009, from http://en.wikipedia.org/wiki/Object-oriented_analysis_and_design
Object-oriented Programming (2009). Wikipedia, the free encyclopedia.
Retrieved Sept 11, 2009, from http://en.wikipedia.org/wiki/Object-oriented_programming
Structured Analysis and Design Technique. (2009). Wikipedia, the free encyclopedia.
Retrieved Sept 11, 2009, from
http://en.wikipedia.org/wiki/Structured_Analysis_and_Design_Technique
Top Dow Design. (2009). Wikipedia, the free encyclopedia.
Retrieved Sept 11, 2009, from http://en.wikipedia.org/wiki/Top-down_design
W. John, Jackson. R, D. Bur. Stephen (2005). Systems Analysis and Design in a Changing World
Retrieved Sept 11, 2009, from http://books.google.com.my/books?id=-
ot62DeCKO4C&pg=PA53&lpg=PA53&dq=traditional+approach+to+system+development&source=bl
&ots=V0wVStRBOw&sig=DC5k1KMU6YyVhsru1Ad_WqEdZYM&hl=en&ei=_0SrSqXjNKWO6AOy39Hd
Bw&sa=X&oi=book_result&ct=result&resnum=5#v=onepage&q=traditional%20approach%20to%20s
ystem%20development&f=false
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