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System Analysis and Development Rev: Feb 15, 2012 Euiho (David) Suh, Ph.D. POSTECH Strategic Management of Information and Technology Laboratory (POSMIT:

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Presentation on theme: "System Analysis and Development Rev: Feb 15, 2012 Euiho (David) Suh, Ph.D. POSTECH Strategic Management of Information and Technology Laboratory (POSMIT:"— Presentation transcript:

1 System Analysis and Development Rev: Feb 15, 2012 Euiho (David) Suh, Ph.D. POSTECH Strategic Management of Information and Technology Laboratory (POSMIT: Dept. of Industrial & Management Engineering POSTECH

2 Contents ※ Discussion Questions 1System Analysis (1)Basic Concepts (2)Modeling 2System Development (1)Systems Development Life Cycle (SDLC) (2)Rapid Application Development (RAD) (3)Prototyping 3Case Study

3 3 Discussion Questions ■Explain the differences between Prototyping and SDLC (Systems Development Life Cycle) ■Explain the Feasibility (Technical, Economic, Operational, and Organizational) ■What is a System Conversion (Parallel, Pilot, Phased, and Plunge)? ■DFD (Data Flow Diagram) vs. ERD (Entity Relationship Diagram) ■RAD (Rapid Application Development) vs. SDLC –When do we use RAD?

4 4 System Analysis (SA) ■Definition of SA –To model the real-world system so that it can be understood ■Goals of SA –To fully specify the problem and application domain without introducing a bias to any particular implementation ■Benefits of SA –It clarifies the requirements of customer(end-user) –It provides a basis for agreement between customer and the developer –It becomes the framework for later design and implementation 1. System Analysis (1) Basic concepts

5 5 Overview of Analysis 1. System Analysis (1) Basic concepts Users Developer Manager Generate Requests User interview Domain knowledge Real-world experience Build Model Problem Statement Data Model Functional Model Behavioral Model Analysis Design

6 6 Problem Statement ■Consist of requirements statement and design & implementation policy ■Requirement statements –Problem scope –Application Context –Assumptions –Performance Needs ■Design & implementation policy –General approach –Algorithms –Data Structures –Architecture 1. System Analysis (1) Basic concepts

7 7 Data Modeling (1/2) ■Data model answers following specific questions –What are the primary data objects to be processed by the system? –What is the composition of each data objects and what attributes describe the object? –Where do the objects currently reside? –What are the relationships between each object and other objects? –What is the relationship between the objects and the processes that transform them ? ■Data modeling methods –ERD(Entity Relationship Diagram) –DD(Data Dictionary) –OM(Object Modeling) : object-oriented modeling method 1. System Analysis (2) Modeling

8 8 Data Modeling (2/2) - ERD 1. System Analysis (2) Modeling Manufacturer Builds Car Dealership Shipper Licenses Stocks Contracts Entity Relationship Cardinality

9 9 Functional Modeling (1/2) ■Functional model shows –How values are computed, without regard for sequencing, decision, or object structure –Which values depend on which other values and the functions that relate them ■Steps for constructing a functional model –Identify input and output values –Show functional dependencies(Using DFD or IDEF0) –Describe functions –Identify constraints ■Identify input and output values –Ex> Input and output values for ATM system 1. System Analysis (2) Modeling Cash card Cash card User ATM bank code, card code Password Transaction kind, Account type, amount cash., receipt., messages System boundary

10 10 Functional Modeling (2/2) ■Describing functions –Ex> Function description for update account function 1. System Analysis (2) Modeling Update account(account, amount, transaction-kind) -> cash, receipt, message If the account on a withdrawal exceeds the current account balance, reject the transaction and dispense no cash If the account on a withdrawal does not exceed the current account balance debit the account and dispense the amount requested If the transaction is a deposit credit the account and dispense no cash If the transaction is a status request dispense no cash In any case, the receipt shows ATM number, date, time, account number, transaction-kind, amount transacted(if any), and new balance

11 11 Behavioral Modeling (1/4) ■Behavioral model –Shows the time-dependent behavior of the system and object in it –Begins by looking for events(externally-visible stimuli & responses) –Is insignificant for a purely static data repository, such as a DB. –Is important for interactive system ■Steps for constructing a Behavioral model –Prepare scenarios of typical interaction sequences –Identify events between objects –Prepare an event trace for each scenario –Build a state diagram 1. System Analysis (2) Modeling

12 12 Behavioral Modeling (2/4) ■Prepare scenarios –Ex> Normal ATM scenario ■Identify Events –Examine scenario to identify all external events. : Events include all signals, inputs, decisions, interrupts, transitions, and actions to or from users or external devices ■Prepare an event trace –Ex> Event trace for ATM scenario (next slide) ■Build a state diagram –Ex> State diagram for ATM (next slide) 1. System Analysis (2) Modeling The ATM asks the user to insert a card; the user insert a cash card. The ATM accepts the card and reads its serial number The ATM requests the password : the user enters “1234” The ATM verifies the serial number and password with the consortium; the consortium checks it with bank “39” and notifies the ATM of acceptance The ATM asks the user to select the kind of transaction ; the user select withdrawal The ATM asks for the amount of cash ; the user enters $100 The ATM asks the consortium to process the transaction ; consortium passes the request to the bank The ATM dispenses cash and asks the user to take it; the user takes the cash The ATM asks whether the user wants to continue; the user indicates no The ATM prints a receipt, ejects the card, and asks the user to take them; the user takes the receipt and the card The ATM asks a user to insert a card

13 13 Behavioral Modeling (3/4) ■Event trace 1. System Analysis (2) Modeling User ATM Consortium Bank Insert card Request password Enter password Verify account Verify card Bank account OK Account OK Request kind Enter kind Request amount Enter amount Process transaction Process bank succeed

14 14 Behavioral Modeling (4/4) ■State diagram 1. System Analysis (2) Modeling Main screen Do : display main screen Insert card [readable] Insert card [unreadable] Do : request password Unreadable Do : Unreadable Card message Enter password Do : verify account Account OK Do: request kind Do : verify account Cancel Enter Kind Cancel Do : canceled message Cancel Enter amount Do : process transaction Card ejected Do : eject card; Request take card Take card Cancel Do : dispense cash; request take cash Do : request continuation Transaction succeed Take cash Bad account Do : bad account message; Finish Do : print receipt Terminate cancel

15 15 Systems Development Life Cycle (SDLC) ■Definition –The overall process of developing information systems through a multi step process from investigation of initial requirements through analysis, design, implementation and maintenance ■Types of SDLC –Waterfall Major methodology of SDLC –Fountain –Spiral ■Outputs from one step → Inputs to next ■Often referred to as the “waterfall” model (The oldest one - early 1970s) 2. System Development (1) SDLC - Introduction to SDLC

16 16 5 Phases of Waterfall Development Method Systems Analysis Systems Designs 2. System Development (1) SDLC - Waterfall Development Method

17 17 Phase 1: Investigation ■Initialization –Management planning, Users’ needs & opportunities ■Formal definition –Objective, motivation, scope, boundaries, constraints, strategy –Verifying a problem or deficiency which really exists, or passing judgment on the new requirement ■Feasibilities studies Technical Feasibility Availability of computing hardware and software to do a particular job Managers’ concerns about the absence of technology in many cases Economic Feasibility Ability of a system to pay for itself in monetary terms No unprofitable spending e.g.) Cost-benefit Analysis, Break-even Analysis, Payback Analysis, NPV Operational Feasibility Ability of the people working within a system to do their jobs in a prescribed manner e.g.) Ability of Users and Participants & Attitudes of Users and Participants Organizational Feasibility How well a proposed e-commerce system helps the company’s plans for developing Web-based sales, marketing, and financial system 2. System Development (1) SDLC - Waterfall Development Method

18 18 Phase 2: Analysis ■What a system should do to meet the needs of users ■Determine requirements –Study current system –Structure requirements and eliminate redundancies ■Requirement Analysis –Functional requirements –Performance requirements ■Generate alternative designs ■Compare alternatives ■Recommend best alternative 2. System Development (1) SDLC - Waterfall Development Method

19 19 ■How the system will accomplish the objective ■User interface Design –Screen –Form –Report –Dialog Design ■Data Design –Data Element structure Design ■Process Design –Program and Procedure Design Phase 3: Design 2. System Development (1) SDLC - Waterfall Development Method

20 20 Phase 4: Implementation ■Evaluating Hardware, Software, and Services –Scoring evaluation system: Used when there are several competing proposals for a hardware or software acquisition ■Software Development or Modification ■Documentation –Major mechanism of communication during development process ■Data Conversion –Correcting incorrect data –Filtering unwanted data –Consolidating data from several data warehouses. ■Testing –Testing & Debugging the Software ■Training 2. System Development (1) SDLC - Waterfall Development Method

21 21 Phase 4: Implementation ■Conversion Running old & new systems for awhile to check validity Safe Parallel Strategy Installed in one part of organization at a time Learning and adapting Pilot Strategy Changing one function at a time in large system e.g. order entry Phased Strategy Starting using entire system Dangerous if errors exist Plunge Strategy 2. System Development (1) SDLC - Waterfall Development Method

22 22 Phase 5: Maintenance ■Modification –Modifying established system due to changes in the system for potential problems or necessary change ■Correcting errors ■Feedback 2. System Development (1) SDLC - Waterfall Development Method

23 23 Pros and Cons of SDLC ■Advantages: –Highly structured, systematic process –Thorough requirements definition –Clear milestone with business management sign-offs ■Disadvantages –Not accounting well for evolving requirements during project –Time-consuming (and costly) process 2. System Development (1) SDLC - Pros and Cons of SDLC

24 24 Rapid Application Development (RAD) ■Definition –Rapid Application Design –A system development methodology created to radically decrease the time needed to design and implement information systems ■Motivation of Rapid Application Development (RAD) –Limitation of SDLC –Pressures for businesses to speed up –Shorter development lifecycles –Competition in changing global environment “Why wait 3 years to develop systems likely to be obsolete upon completion?” RAD methodology was born! 2. System Development (2) RAD

25 25 The 4 Essentials of RAD (1/2) ■Management –Executives, Support for the RAD ■People –Participation in JAD type –Specialized team for RAD: SWAT(“Skilled With Advanced Tools”)  Joint application design (JAD) Group Decision Support System Users, Managers and Analysts work together for several days System requirements are reviewed Structured meetings ■Methodologies –RAD life cycle: Users play key roles ■Tools –Fourth-generation languages and CASE tools that facilitate prototyping and code generation  Computer-Aided Software Engineering (CASE) Any software tool to transfer some of the systems development workload from the human developer to the computer by automating one or more steps of a software development methodology 2. System Development (2) RAD

26 26 RAD Life Cycle JAD session to develop basis design CASE tool is used Delivery of new system to users JRP(Joint Requirement Planning) workshops to agree requirements, overall planning Executives, managers, and users determine requirements Generate code End users validate design 2. System Development (2) RAD

27 27 Prototyping ■Definition –The overall process of developing IS, which enables creation of system (or part of system) more quickly, then revising after users have tried it ■Selected features: Only some essential features included in prototype, more added later 2. System Development (3) Prototyping

28 28 Prototyping Life Cycle Prototype cycle 2. System Development (3) Prototyping

29 29 Pro and Cons of Prototyping ■Advantages –Improved communications between the developer and user –A more active role of users in system development –Less time and effort of information specialists and user in developing the system –Much easier implementation due to the user’s understanding about what to expect ■Disadvantages –Lack of security and control features in end prototype –Possibility that prototyping may not undergo as rigorous testing –Possibility of less complete final documentation –Bigger difficulty to manage user expectations 2. System Development (3) Prototyping

30 30 3 Types of System Development SDLC RAD Prototyping SPEED STABILITY Large and complex system Hybrid type of SDLC and Prototyping When requirements are hard to define Trade-off 2. System Development (3) Prototyping

31 31 Case Study 3. Case Study

32 32 Reference ■O’Brien & Marakas, “Introduction to Information Systems – Fifteenth Edition”, McGraw – Hill, Chapter 10, pp. 404~450O’Brien & Marakas, “Introduction to Information Systems – Fifteenth Edition”, McGraw – Hill, Chapter 10, pp. 404~450 ■Hyungjong Roh, “System Development Methods (PPT slide)”Hyungjong Roh, “System Development Methods (PPT slide)”

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