Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition 8 C H A P T E R PROCESS MODELING

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition Chapter EightProcess Modeling Define process modeling and explain its benefits. Recognize and understand the basic concepts and constructs of a process model. Read and interpret a data flow diagram. Explain when to construct process models and where to store them. Understand how to describe processes using structured English Know how to make and use a decision table

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition Chapter Map

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition Process Modeling and DFDs Process modeling is a technique for organizing and documenting the structure and flow of data through a system’s processes, and/or the logic, policies, and procedures to be implemented by a system’s processes. A data flow diagram (DFD) is a tool (and type of process model) that depicts the flow of data through a system and the work or processing performed by that system. DFDs have become a popular tool for business process redesign.

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition Simple Data Flow Diagram

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition Differences Between DFDs and Flowcharts Processes on DFDs can operate in parallel (at-the- same-time) –Processes on flowcharts execute one at a time DFDs show the flow of data through a system –Flowcharts show the flow of control (sequence and transfer of control) Processes on one DFD can have dramatically different timing –Processes on flowcharts are part of a single program with consistent timing

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition Systems Thinking Systems thinking is the application of formal systems theory and concepts to systems problem solving. DFDs are a tool that supports systems thinking.

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition Process Concepts A process is work performed on, or in response to, incoming data flows or conditions. A System is a Process

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition System Decomposition Decomposition Decomposition is the act of breaking a system into its component subsystems, processes, and subprocesses. Each level of abstraction reveals more or less detail.

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition Decomposition Diagrams A decomposition diagram or hierarchy chart shows the top- down, functional decomposition of a system.

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition Types of Logical Processes A function is set of related and ongoing activities of a business. An event (or transaction) is a logical unit of work that must be completed as a whole (as part of a function). An elementary process (or primitive process) is a discrete, detailed activity or task required to respond to an event. Usually, several such tasks must be completed to respond to an event.

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition Common Process Errors on DFDs

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition PROBLEMS WITH NATURAL ENGLISH 1 Source: Adapted from Matthies, Leslie, The New Playscript Procedure, (Stamford, CT: Office Publications, Inc. 1977) Problems with Natural English Many of us do not write well, and we also tend not to question our writing abilities. Many of us are too educated! It’s often difficult for a highly educated person to communicate with an audience that may not have had the same educational opportunities. For example, the average college graduate (including most analysts) has a working vocabulary of 10,000 to 20,000 words; on the other hand, the average non-college graduate has a working vocabulary of around 5,000 words. Some of us write everything like it was a program. If business procedures required such precision, we’d write everything in a programming language. Too often, we allow the jargon and acronyms of computing to dominate our language. English statements frequently have an excessive or confusing scope. How would you carry out this procedure: “If customers walk in the door and they do not want to withdraw money from their account or deposit money to their account or make a loan payment, send them to the trust department.” Does this mean that the only time you should not send the customer to the trust department is when he or she wishes to do all three of the transactions? Or does it mean that if a customer does not wish to perform at least one of the three transactions, that customer should not be sent to the trust department? We overuse compound sentences Consider the following procedure: “Remove the screws that hold the outlet cover to the wall. Remove the outlet cover. Disconnect each wire from the plug, but first make sure the power to the outlet has been turned off.” An unwary person might try to disconnect the wires prior to turning off the power! Too many words have multiple definitions. Too many statements use imprecise adjectives. For example, an loan officer asks a teacher to certify that a student is in good academic standing. What is good? Conditional instructions can be imprecise. For example, if we state that “all applicants under the age of 19 must secure parental permission,” do we mean less than 19, or less than or equal to 19? Compound conditions tend to show up in natural English. For example, if credit approval is a function of several conditions: credit rating, credit ceiling, annual dollar sales for the customer in question, then different combinations of these factors can result in different decisions. As the number of conditions and possible combinations increases, the procedure becomes more and more tedious and difficult to write.

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition 1. For each CUSTOMER NUMBER in the data store CUSTOMERS: a. For each LOAN in the data store LOANS that matches the above CUSTOMER NUMBER: 1) Keep a running total of NUMBER OF LOANS for the CUSTOMER NUMBER. 2) Keep a running total of thw ORIGINAL LOAN PRINCIPALfor the CUSTOMER NUMBER. 3) Keep a running total of CURRENT LOAN BALANCE for the CUSTOMER NUMBER. 4) Keep a running total of AMOUNTS PAST DUE for the CUSTOMER NUMBER. b. If the TOTAL AMOUNTS PAST DUE for the CUSTOMER NUMBER is greater than $ then: 1) Write the CUSTOMER NUMBER and all their data attributes as described in the data flow LOANS AT RISK. Else 1) Exclude the CUSTOMER NUMBER and data from the data flow LOANS AT RISK. Structured English Structured English is a language and syntax, based on the relative strengths of structured programming and natural English, for specifying the underlying logic of elementary processes on DFDs.

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition Structured English Constructs (Part 1)

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition Structured English Constructs (Part 2) complex logic in which rows represent conditions

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition Structured English Constructs (Part 3)

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition Policies and Decision Tables A policy is a set of rules that governs some process of the business. A decision table is a tabular form of presentation that specifies a set of conditions and their corresponding actions (as required to implement a policy).

Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS5th Edition A Simple Decision Table