Chapter 8 Logic Requirements Modern Systems Analysis and Design Fifth Edition Jeffrey A. Hoffer Joey F. George Joseph S. Valacich Chapter 8 Logic Requirements

Learning Objectives Use Structured English as a tool for representing steps in logical processes in data flow diagrams. Use decision tables to represent the logic of choice in conditional statements. Chapter 8 © 2008 by Prentice Hall

Learning Objectives (Cont.) Select among Structured English and decision tables for representing processing logic. Understand how logic modeling techniques apply to the development of electronic commerce applications. Chapter 8 © 2008 by Prentice Hall

Logic Modeling Data flow diagrams do not show the logic inside the processes. Logic modeling involves representing internal structure and functionality of processes depicted on a DFD. Logic modeling can also be used to show when processes on a DFD occur. Chapter 8 © 2008 by Prentice Hall

Modeling a System’s Logic Chapter 8 © 2008 by Prentice Hall

Deliverables and Outcomes Structured English representation of process logic. Decision Tables representation. Sequence diagram. Activity diagram. Chapter 8 © 2008 by Prentice Hall

Modeling Logic with Structured English Structured English: modified form of English language used to specify the logic of information system processes. No single standard. Typically relies on action verbs and noun phrases and contains no adjectives or No specific standards. Chapter 8 © 2008 by Prentice Hall

Modeling Logic with Structured English (Cont.) Chapter 8 © 2008 by Prentice Hall

Modeling Logic with Structured English (Cont.) Chapter 8 © 2008 by Prentice Hall

Modeling Logic with Decision Tables Decision table: a matrix representation of the logic of a decision which specifies the possible conditions for the decision and the resulting actions. Best used for complicated decision logic. Chapter 8 © 2008 by Prentice Hall

Modeling Logic with Decision Tables (Cont.) Chapter 8 © 2008 by Prentice Hall

Modeling Logic with Decision Tables (Cont.) Condition stubs: that part of a decision table that lists the conditions relevant to the decision. Action stubs: that part of a decision table that lists the actions that result for a given set of conditions. Chapter 8 © 2008 by Prentice Hall

Modeling Logic with Decision Tables (Cont.) Rules: that part of a decision table that specifies which actions are to be followed for a given set of condition. Indifferent condition: in a decision table, a condition whose value does not affect which actions are taken for two or more rules. Chapter 8 © 2008 by Prentice Hall

Modeling Logic with Decision Tables (Cont.) Procedure for Creating Decision Tables Name the condition and the values that each condition can assume. Name all possible actions that can occur. List all possible rules. Define the actions for each rule. Simplify the table. Chapter 8 © 2008 by Prentice Hall

Modeling Logic with Decision Tables (Cont.) Chapter 8 © 2008 by Prentice Hall

Deciding Among Structured English and Decision Tables Criteria Structured English Decision Tables Determining Conditions and Actions Second Best Third Best Transforming Conditions and Actions into Sequence Best Checking Consistency and Completeness Chapter 8 © 2008 by Prentice Hall

Electronic Commerce Application: Logic Modeling Pine Valley Furniture development methodology dictated that the logic within each unique processes be represented. Structured English was chosen for modeling the logic. Chapter 8 © 2008 by Prentice Hall

Electronic Commerce Application: Logic Modeling (Cont.) Figure 8-8 Level-0 DFD for the WebStore system Chapter 8 © 2008 by Prentice Hall

Electronic Commerce Application: Logic Modeling (Cont.) Chapter 8 © 2008 by Prentice Hall

Summary In this chapter you learned how to: Use Structured English as a tool for representing steps in logical processes in data flow diagrams. Use decision tables to represent the logic of choice in conditional statements. Select among Structured English and decision tables for representing processing logic. Understand how logic modeling techniques apply to the development of electronic commerce applications. Chapter 8 © 2008 by Prentice Hall