Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall Process Specifications and Structured Decisions Systems Analysis and Design, 8e Kendall & Kendall 9

Kendall & KendallCopyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall9-2 How Process Specifications Relate to the Data Flow Diagram (Figure 9.1)

Kendall & KendallCopyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall9-3 Structured English Used when the process logic involves formulas or iteration, or when structured decisions are not complex Based on structured logic and simple English statements such as add, multiply, and move

Kendall & KendallCopyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall9-4 Writing Structured English Express all logic in terms of : Sequential Structures Decision Structures Case Structures Iterations Use and capitalize accepted keywords such as IF, THEN, ELSE, DO, and PERFORM. Clarify the logical statements.

Kendall & KendallCopyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall9-5 Examples of Logic Expressed in a Sequential Structure Process 1.0 :Compute Gross Pay INPUT hours worked MULTIPLY hours worked by pay rate OUTPUT gross pay.

Kendall & KendallCopyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall9-6 Examples of Logic Expressed in a Decision Structure Process 2.1: Calculate Over Time RECEIVE Overtime_Pay_Amount_Request from Employee GET Employee’s Employee_Time_Card for Desired_Week from Employee File BEGIN IF IF Total_Overtime_Hours > 0 THEN Overtime_Pay_Amount = Total_Overtime_Hours * Standard_Overtime_Pay_Rate ELSE Overtime_Pay_Amount =0 END-IF SEND Overtime_Pay_Amount to Employee

Kendall & KendallCopyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall9-7 Examples of Logic Expressed in a Case Structure Process 2.3: Determine Salestax Input State SELECT CASE CASE 1 (State = "AZ") Salestax = CASE 2 (State = "CA") Salestax = 0.05 END CASE OUTPUT Salestax

Kendall & KendallCopyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall9-8 Examples of Logic Expressed in an Iteration Process 1.0: Calculate Gross Pay INPUT Employee Record from Employees _File DO WHILE there more employee records to process READ next employee record READ hours worked READ pay rate MULTIPLY pay rate by hours worked END DO OUTPUT Gross Pay

Kendall & KendallCopyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall9-9 Advantages of Structured English Clarifying the logic and relationships found in human languages An effective communication tool, it can be taught to and understood by users in the organization

Kendall & KendallCopyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall9-10 Decision Trees Decision trees are used when complex branching occurs in a structured decision process. Trees are also useful when it is essential to keep a string of decisions in a particular sequence.

Kendall & KendallCopyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall9-11 Drawing Decision Trees Identify all conditions and actions and their order and timing (if they are critical). Begin building the tree from left to right, making sure you list all possible alternatives before moving to the right.

Kendall & KendallCopyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall9-12 Example Decision Tree

Kendall & KendallCopyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall9-13 Decision Tree Advantages The order of checking conditions and executing actions is immediately noticeable. Conditions and actions of decision trees are found on some branches but not on others. Decision trees are more readily understood by others in the organization.

Kendall & KendallCopyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall9-14 Selecting a Structured Decision Analysis Technique Use structured English when there are many repetitious actions or when communication to end users is important. Use decision trees when the sequence of conditions and actions is critical or when not every condition is relevant to every action (the branches are different).

Kendall & KendallCopyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall9-15 Summary Process specifications Decision analysis Structured English Logic is expressed in sequential structures, decision structures, case structures, or iterations.

Kendall & KendallCopyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall9-16 Summary (Continued) Decision trees Consist of nodes and branches

Kendall & KendallCopyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall9-17 Summary (Continued) Decision analysis advantages Structured English is useful when many actions are repeated and when communicating with others is important. Decision tables provide complete analysis of complex situations while limiting the need for change attributable to impossible situations, redundancies, or contradictions. Decision trees are important when proper sequencing of conditions and actions is critical and when each condition is not relevant to each action.

9-18 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in the United States of America. Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall