creating new system models file design fundamentals relational databases revisited file design for sunrise systems form design revisited the cornucopia case portfolio project Systems Analysis and Design for the Small Enterprise section III Design

Chapter Objectives When you complete this chapter you will be able to: Develop the new system process model (DFD) from the preliminary USD Develop the new system data model (ERD) and object model (OM) Develop estimates of the resource requirements associated with file processing design Design graphical user interface dialogs (GUIDs) and screen forms to access system files and processes 2

Creating New System Models The preliminary USD sketch provides the basis for the first joint application design session Its informal structure invites the user to suggest changes and actively participate in the design process Developing other new system models, such as the DFD and ERD, is made easier as the USD is refined during the JAD sessions 3

Figure 8-1: Design Activities 4

Figure 8-2: Sunrise Systems GUID Design 5

File Design Fundamentals 6 File design is one of the first detailed design activities The new file designs provide structures used to create sample input and output forms and reports In practice, design work switches among file, output, and input design

7 Figure 8-3: Traditional File Types

8 4GL Products and File Types

Data Structure Hierarchy 9

10 File Design Steps

Relational Databases Revisited 11 The database is at the heart of the information system Microsoft Access is a relational database management software product suitable for a small- enterprise information system project

12 Database Table Definition with MS Access

13 Database Table Relationships with MS Access

File Design for Sunrise Systems 14 Three files appear on the DFD: Portfolio Notes, Portfolio Transactions, and Portfolio Performance These files appear on the preliminary ERD, but they have many-to-many relationships A fourth file (Portfolio Investor) is added to the ERD to normalize the relationships Portfolio Investor is a master file, while the other three are transaction files

15 Sunrise Systems New System Preliminary ERD DFD

16 Sunrise Systems New System Normalized ERD

17 Form Design Revisited Database master files require maintenance forms to allow for the addition of new records and changes to existing records Database transaction files require processing forms for data input and transaction processing

18 Form Design Steps 1.Draft the basic screen design templates 2.Determine what data the user must supply to initiate updates for one of the master files 3.Determine which file data the user needs to verify the master file update 4.Determine how to inform the user about errors 5.Develop a set of sample “dialog sequences” (GUIDs) required to implement Steps 2, 3, and 4 6.Perform Steps 2 – 5 for one of the transaction file data entry operations 7.Sketch a menu tree diagram showing how all the master and transaction file screen forms interact 8.Create one master file update screen form 9.Create one transaction file update screen form 10.Work with the user to review and revise the design of the forms

The Cornucopia Case The USD provides a springboard for discussions with the user about the new system design. The analysts point out that customer maintenance and correspondence are new, as is the Internet connection. Further, the sales subsystem now includes a CD inventory maintenance and automatic ordering capability. 19

20 Cornucopia New System First-Level DFD Enlarge

21 Cornucopia New System ERD

22 Cornucopia New System OM Order Detail CD MasterCD TransactionCustomer Master Supplier MasterCD Trans Detail

23 Cornucopia New System Menu Tree

24 Cornucopia CD Update Form

25 Cornucopia CD Sales Form

26 Cornucopia CD Order Form

27 Cornucopia Project Status – Week 5

Chapter Summary 28 New system design begins with the USD The DFD and ERD models are based on the USD Database design is based on the ERD Screen forms are required to maintain database master files and transaction files Generally speaking, database master file forms are easy to develop and database transaction file forms are difficult to develop

29 Cornucopia New System First-Level DFD Return

30 Cornucopia New System First-Level DFD Return