REQUIREMENTS ANALYSIS 1 Context of System Analysis Requirements

REQUIREMENTS ANALYSIS 1

Context of System Analysis

Requirements Analysis l The process and technique that a group of system analyst utilizes to identify, analyze, and understand system requirements – System’s requirements specify what the system must do as well as what property or quality the system must have. l One of the early IS development phases. – Data Model: one of the primary activities for the requirements analysis phase of the DB System Development 3

Relative Cost to Fix an Error 4

Relative Cost to Fix an Error (BASED ON CONSULTANT REPORTS & TRADE LITERATURE) 5 4 2 1 N TI O TA LE N N PL E O PO ST I M C PR O G R A VE R M M SI O IN N G 0 A A NA N L D Y D SI ES S IG N COSTS 3 5

Results of Incorrect Requirements Analysis l The system may cost more than projected – Denver airport Baggage-Handling IS l The system may be delivered later than promised. l The system may not meet the users’ expectations and that dissatisfaction may cause them not to use it. l Once in production, the costs of maintaining and enhancing the system may be excessively high. – California DMV system 6

Very Difficult to Manage l Over the lifetime of the project, it is very common for new requirements to emerge and existing requirements to change. l 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. 7

System Development is about Documentation……. l Data model is part of an official DB document (blue print of the DB) l Department of Justice – System development is about “documentation…. . Documentation…… documentation” – See the Department of Justice SDLC documentation on the course website 8

IS Architecture l 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 9

Information Systems Architecture Data Architecture Process Architecture 10

How to develop IS Architecture? l How the foundation of IS architecture should be developed? 1. Strategic Management q Mission statement: root of strategic Mngt. 2. Corporate Strategy 3. IS Strategy 4. IS architecture q Data (ERD) and Process (DFD) Architectures 11

What is 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)

What is Data Flow Diagram? l A DFD is a graphical representation of the "flow" of data through an information system. – How data enter a system and transformed in that system l What is a Data Flow Diagram and Why Do You Need One? (2: 28)

Creating Data Flow Diagram Lemonade Stand Example

Creating Data Flow Diagrams Example The operations of a simple lemonade stand will be used to demonstrate the creation of data flow diagram. Steps: 1. Create a list of activities 2. Construct Context Level DFD (identifies sources and sink) 3. Construct Level 0 DFD (identifies manageable sub processes ) 4. Construct Level 1 - n DFD (identifies actual data flows and data stores )

Creating Data Flow Diagrams Example 1. 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 Labor

Creating Data Flow Diagrams Example Create a context level diagram identifying the sources and sinks (users). 2. Construct Context Level DFD (identifies sources and sink) Context Level DFD Order Customer Order Serve Product Collect Payment Produce Product Store Product Order Raw Materials Pay for Labor CUSTOME R Product Served 0. 0 Lemona de System Payment Received Goods Payment Sales Forecast Production EMPLOYE Schedule E Pay Time Worked Purchase Order VENDOR

Creating Data Flow Diagrams Example Create a level 0 diagram identifying the logical subsystems that may exist. 3. Construct Level 0 DFD (identifies manageable sub processes ) Level 0 DFD 1. 0 Sale Customer Order Serve Product Collect Payment CUSTOME R Produce Product Store Product Order Raw Materials Pay for Labor Sales Forecast Customer Order Product Ordered Payment 2. 0 Production Producti Schedule Product Served on Received Goods VENDOR Purchase Order EMPLOYE E Inventory 3. 0 Procurement Payment Order Decisions Pay 4. 0 Payroll Time Worked

Creating Data Flow Diagrams Example Create a level 1 decomposing the processes in level 0 and identifying data stores. 4. Construct Level 1 - n DFD (identifies actual data flows and data stores ) Level 1 DFD CUSTOME R Customer Order Serve Product Collect Payment Produce Product Store Product Order Raw Materials Pay for Labor ORDER 1. 1 Record Order Severed Order Payment 1. 2 Receive Paymen t PAYMENT Request for Forecast 1. 3 Produce Sales Forecast

Process Decomposition 0. 0 Lemona de System Context Level 1. 0 Sale 1. 1 Record Order 1. 2 Receive Paymen t 2. 0 Producti on 2. 1 Serve Product 2. 2 Produce Product 2. 3 Store Product 3. 0 Procurement 3. 1 Produce Purchas e Order 3. 2 Receive Items 3. 3 Pay Vendor 4. 0 Payroll 4. 1 Record Time Worked 4. 2 Calculat e Payroll 4. 3 Pay Employ ee Level 0 Level 1

Why not using Flow Chart? l Complex Logic: – Many of today’s MIS 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 l Alterations and Modifications: – If alterations are required the flowchart may require re-drawing completely. This is quite time and effortconsuming. 22

Why not using Flow Chart? l Reproduction: – As the flowchart symbols cannot be typed, reproduction of flowchart becomes a problem. l The essentials of what is done can easily be lost in the technical details of how it is done. l Factors that affect the sequence are not included. 23