Traditional Approach Vs Oo Approach

SYSTEM ANALYSIS & DESIGN (MTD 2033)

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 : Controls

Inputs

Function

Outputs

Mechanisms 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.

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SYSTEM ANALYSIS & DESIGN (MTD 2033)

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 Stand Up

Turn Right

Walk To the Window -

A decision where one set of statements or another set of statement executes Look outside

Is it raining?

No

Wear sunscreen

Yes Take an umbrella

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SYSTEM ANALYSIS & DESIGN (MTD 2033)

-

A repetition of a set of statement

Take a step No Are you at your destination?

Yes Stop 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.

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SYSTEM ANALYSIS & DESIGN (MTD 2033)

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. -

ii.

Top programming or modular programming

Structured design (SD) Methods for analyzing and converting business requirements into specifications and ultimately, computer programs, hardware configurations and related manual procedures

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SYSTEM ANALYSIS & DESIGN (MTD 2033)

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.

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SYSTEM ANALYSIS & DESIGN (MTD 2033)

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.

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SYSTEM ANALYSIS & DESIGN (MTD 2033)

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

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SYSTEM ANALYSIS & DESIGN (MTD 2033)

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 :

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SYSTEM ANALYSIS & DESIGN (MTD 2033)

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

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SYSTEM ANALYSIS & DESIGN (MTD 2033)

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.

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SYSTEM ANALYSIS & DESIGN (MTD 2033)

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

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SYSTEM ANALYSIS & DESIGN (MTD 2033)

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.

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SYSTEM ANALYSIS & DESIGN (MTD 2033)

Traditional Approach VS Object Oriented Approach Categories Overview

Traditional Approach Computer systems viewed as a collection of computer programs

Object Oriented Approach Similar things can be grouped and classified. Same goes for related things.

Includes many variations based on techniques used to develop information system with structured and modular programming Analysis

Analysis tools

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

Data Flow Diagrams (DFD) Context Diagram

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) Writing statements in a programming language to define what each type of object does, including the messages that the objects send to each other

Data Dictionary

Programming

Programming construct

One that has one beginning and one ending and each step of three programming constructs

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

Design

Design technique

Similarity

Benefits

Information hiding Inheritance Interface Polymorphism Methods for analyzing and converting Defining all of the types of object necessary business requirements into specifications and to communicate with people and devices in ultimately, computer programs, hardware the system , showing how objects interact to configurations and related manual complete tasks and refining the definitions of procedures each type of object so it can be implemented with specific language or environment Structured Design Conceptual model Use case System Sequence Diagram User interface documentations Relational data model identifies business events defines users’ requirements data modeling concepts & techniques user interfaces Easy to maintain (if an error occurs in the Increase in productivity has not kept pace output, it is easy to identify the errors with increased demand for speedy delivery of generated from which module of the entire new software. program) Existing software needs massive maintenance DFDs have become a popular tool for effort to keep them operational. business process redesign. Some companies spend up to 80% of IT resources for maintenance. Very optimized way of processing (each Customers get better systems at less cost. programmer has to apply their own Projects are done on time.

SYSTEM ANALYSIS & DESIGN (MTD 2033)

Disadvantages

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

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)

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 Retrieved Sept 11, 2009, from http://www.cs.toronto.edu/~jm/2507S/Notes04/SADT.pdf

(SADT)

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 Retrieved Sept 11, 2009, http://en.wikipedia.org/wiki/Structured_Analysis_and_Design_Technique Top

Dow Design. (2009). Wikipedia, the free Retrieved Sept 11, 2009, from http://en.wikipedia.org/wiki/Top-down_design

free

encyclopedia. from

encyclopedia.

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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SYSTEM ANALYSIS & DESIGN (MTD 2033)

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