REQUIREMENTS ANALYSIS This repository of slides is intended to support the named chapter. The slide repository should be used as follows: Copy the file to a unique name for your course and unit. Edit the file by deleting those slides you don’t want to cover, editing other slides as appropriate to your course, and adding slides as desired. Print the slides to produce transparency masters or print directly to film or present the slides using a computer image projector. Each slide includes instructor notes. To view those notes in PowerPoint, click-left on the View Menu; then click left on Notes View sub-menu. You may need to scroll down to see the instructor notes. The instructor notes are also available in hardcopy as the Instructor Guide to Accompany Systems Analysis and Design Methods, 6/ed.
Requirements Analysis One of the early IS development phases. ERD: part of requirements analysis phase The process and technique that a group of system analyst uses to identify, analyze, and understand system requirements System’s requirements specify what the information system must do, or what property or quality the system must have. What do bank tellers need and want from the new or renovated system? Critical phase for reducing the system cost No additional notes.
Requirements Analysis for RDS Identify essential information Remove redundant, unimportant details Clarify unclear natural language statements Distinguish data and operations Data: ERD (entity relationship diagram) Operation: DFD (data flow diagram) Example: Movie Video Rental (next slide)
Example: Movie Video Rental MovieClub is a video rental store that has a variety of films for every age group. The manager of the club has a database application installed to manage the store more efficiently. The database application supports the main business operations in the store, namely, video checkout and return, inventory management, and membership management. It is also used to answer possible customer queries about the availability of certain films. The following is a description of the conceptual model of the video rental database at MovieClub. The video rental database contains information about members, films, video tapes, and rentals. The information on members includes the name, address, phone number, and the expiration date of the membership. A member is identified with a unique membership number.
Example con’t Films have identification numbers and are described by title, length (in minutes), category (drama, comedy, action, sci-fi, etc.), version (English, French, Spanish), and production date. There are usually several video tapes of each film. Every video tape is identified by a unique tape identification. Other information kept in the database about the tape includes type (VHS or DVD), and the rate at which in can be rented. A member can rent several video tapes at the same time. Obviously, the same video tape can be rented by several members on different dates. Tape rental information, represented in the database, consists of checkout date, and duration (in days). It is important to notice that the same video tape can be rented by the same member more than once.
Essential information customers, tapes, movies, ... movies have many copies tape (or DVD) contains exactly one movie several video tapes of each film identification (id)
Redundant, unimportant details ….”manager of the club has a database application installed to manage the store more efficiently….” (unimportant) ..”same video tape can be rented by several members..” (redundant) A member can rent several video tapes at the same time. DVDs on shelf (we do not design a tape robot!) Names of the categories (maybe not now! But later)
Relative Cost to Fix an Error
Relative Cost to Fix an Error (BASED ON CONSULTANT REPORTS & TRADE LITERATURE) 1 2 3 4 5 COSTS ANALYSIS AND DESIGN PROGRAMMING CONVERSION POSTIMPLELENTATION
Results of Incorrect Requirements Analysis The system may cost more than projected The system may be delivered later than promised. The system may not meet the users’ expectations and that dissatisfaction may cause them not to use it. Once in production, the costs of maintaining and enhancing the system may be excessively high. No additional notes.
Very Difficult to Manage Over the lifetime of the project, it is very common for new requirements to emerge and existing requirements to change. Studies have shown that over the life of a project as much as 50 percent or more of the requirements will change before the system is put into production.
Fact-Finding Technique Sampling of existing documentation, forms, and databases. Research and site visits. Observation of the work environment. Questionnaires. Interviews. Prototyping. Joint requirements planning (JRP).
System Development Documentation Data model becomes an official blue print (system document) of the DB Department of Justice See the Department of Justice documentation on the course website System development is about “documentation….. Documentation…… documentation”
IS Architecture Can be divided into data and process architectures Data architecture by Data Model ERD: focus on the optimal organization of data, not on where or how data are used Process architecture by Process Model DFD (Data Flow Diagram): focus on how and when data are moved Diagram for IS architecture UCD (Use Case Diagram)
What is Use Case Diagram? The UCD is for the modeling of real-world objects and systems. It is a graphic depiction of the interactions between stakeholders and a system Focus on “What a system does”…”rather than how a system does.” In other words, it is a methodology used in system analysis to identify, clarify, and organize OVERALL SYSTEM REQUIREMENTS.
UCD for Bank ATM http://www.uml-diagrams.org/bank-atm-uml-use-case-diagram-example.html?context=uc-examples Chapter 7 - Modeling System Requirements With Use Cases
Creating Data Flow Diagram Lemonade Stand Example
Creating Data Flow Diagrams Example Steps: The operations of a simple lemonade stand will be used to demonstrate the creation of data flow diagram. Create a list of activities Construct Context Level DFD (identifies sources and sink) Construct Level 0 DFD (identifies manageable sub processes ) Construct Level 1- n DFD (identifies actual data flows and data stores )
Creating Data Flow Diagrams Example Create a list of activities Think through the activities that take place at a lemonade stand. Customer Order Serve Product Collect Payment Produce Product Store Product Order Raw Materials Pay for Raw Materials Pay for Labor
Creating Data Flow Diagrams Example Construct Context Level DFD (identifies sources and sink) Create a context level diagram identifying the sources and sinks (users). Context Level DFD Sales Forecast CUSTOMER 0.0 Lemonade System EMPLOYEE Order Production Schedule Customer Order Serve Product Collect Payment Produce Product Store Product Order Raw Materials Pay for Raw Materials Pay for Labor Product Served Pay Payment Time Worked Received Goods Payment Purchase Order VENDOR
Creating Data Flow Diagrams Example Construct Level 0 DFD (identifies manageable sub processes ) Create a level 0 diagram identifying the logical subsystems that may exist. Level 0 DFD 1.0 Sale Sales Forecast Customer Order Serve Product Collect Payment Produce Product Store Product Order Raw Materials Pay for Raw Materials Pay for Labor Customer Order Product Ordered CUSTOMER Payment 2.0 Production EMPLOYEE Production Schedule Product Served Inventory Received Goods VENDOR 3.0 Procure-ment Purchase Order Order Decisions Payment Pay Time Worked 4.0 Payroll
Creating Data Flow Diagrams Example Construct Level 1- n DFD (identifies actual data flows and data stores ) Create a level 1 decomposing the processes in level 0 and identifying data stores. Level 1 DFD CUSTOMER Customer Order Request for Forecast Customer Order Serve Product Collect Payment Produce Product Store Product Order Raw Materials Pay for Raw Materials Pay for Labor ORDER 1.1 Record Order 1.3 Produce Sales Forecast Severed Order Payment Sales Forecast 1.2 Receive Payment PAYMENT
Process Decomposition 1.0 Sale 1.1 Record Order 1.2 Receive Payment 2.0 Production 2.1 Serve Product 2.2 Produce Product 2.3 Store Product 0.0 Lemonade System 3.0 Procure-ment 3.1 Produce Purchase Order 3.2 Receive Items 3.3 Pay Vendor 4.0 Payroll 4.1 Record Time Worked 4.2 Calculate Payroll 4.3 Pay Employee Context Level Level 0 Level 1
Why not using Flow Chart? Complex Logic: Many of today’s IS program logic is quite complicated. In that case, flowchart becomes complex and clumsy because the complexity can grow exponentially. Not so recommendable in MIS & CS Alterations and Modifications: If alterations are required the flowchart may require re-drawing completely. This is quite time and effort-consuming.
Why not using Flow Chart? Reproduction: As the flowchart symbols cannot be typed, reproduction of flowchart becomes a problem. The essentials of what is done can easily be lost in the technical details of how it is done. Factors that affect the sequence are not included.
How to develop IS Architecture? How the foundation of IS architecture should be developed? IS architecture IS Strategy Corporate Strategy Strategic Management Mission statement: root of strategic Mngt.
Strategic Management Highest level of overall planning is the continuous planning, monitoring, analysis and assessment of all that is necessary for an organization to meet its goals & objectives and to position a firm to succeed in its market environment.
Strategic Management Process (con’t) Components of Strategic Management Process Strategic Management Process (4:35) Website: Strategic Management Process