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SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

C H A P T E R

8
Irwin/McGraw-Hill

PROCESS
MODE...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Chapter Eight
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Whitten Bentley Dittman

Process ...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Chapter Map

Irwin/McGraw-Hill

Copyright © 2000...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Models: Logical and Physical

A model is a repre...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Why Logical System Models

• Logical models remo...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Process Modeling and DFDs

Process modeling is a...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Simple Data Flow Diagram

Irwin/McGraw-Hill

Cop...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Differences Between DFDs and Flowcharts

• Proce...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Systems Thinking

Systems thinking is the applic...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Process Concepts

A process is work
performed on...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Decomposition

Decomposition is the
act of break...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Decomposition Diagrams

A decomposition
diagram ...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Types of Logical Processes

• A function is set ...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Common Process Errors on DFDs

Irwin/McGraw-Hill...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Problems with Natural English
PROBLEMS WITH NATU...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Structured English

Structured English is a lang...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Structured English Constructs (Part 1)

Irwin/Mc...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Structured English Constructs (Part 2)

complex ...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Structured English Constructs (Part 3)

Irwin/Mc...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Policies and Decision Tables

A policy is a set ...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

A Simple Decision Table

Irwin/McGraw-Hill

Copy...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Data Flows & Control Flows

• A data flow repres...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Data Flow Packet Concept

Irwin/McGraw-Hill

Cop...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Composite and Elementary Data Flows

Irwin/McGra...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Data Flows to and from Data Stores

Irwin/McGraw...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Illegal Data Flows

Irwin/McGraw-Hill

Copyright...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Data Structures

Data flows can be defined by da...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

A Data Structure for a Data Flow
DATA STRUCTURE
...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Data Structure Constructs
Data Structure

Format...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Data Structure Constructs (concluded)

Data Stru...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Data Types and Domains

Data attributes should b...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Diverging and Converging Data Flows

• A divergi...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Diverging and Converging Data Flows

Irwin/McGra...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

External Agents

• An external agent defines a p...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Data Stores

• A data store is an inventory of d...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

When to Draw Process Models

• Strategic systems...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Classical Structured Analysis
1. Draw top-down p...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Modern Structured Analysis
1. Draw a context DFD...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Structured Analysis Diagram Progression

Irwin/M...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Structured Analysis Diagram Progression

Irwin/M...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Structured Analysis Diagram Progression

Irwin/M...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

CASE for DFDs (Sample Screen)

Irwin/McGraw-Hill...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

SoundStage Context DFD
Accounts
Receivable

Prom...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

SoundStage Functional Decomposition Diagram
Memb...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Events

• Events define processes needed to resp...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Use Cases

• Use cases are based upon object-ori...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Use Case List
Actor

Event (or Use Case)

Trigge...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Use Case List (continued)
Actor

Event (or Use C...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Use Case List (continued)

Actor

Event (or Use ...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Event Decomposition Diagram (partial)
Member
Ser...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

External Event DFD

Club
Member

Member Change
o...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

External Event DFD (more complex)
Members

Updat...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Temporal Event DFD
Agreements

Members

Fulfillm...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

System DFD

Whitten Bentley Dittman

(see book for more readable copy)

T...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Primitive DFD (see book for more readable copy)
...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Data Structure for a Primitive Data Flow

Data F...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

Logic for a Primitive Process
Process
Logic

Irw...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

8.30 Data to Process CRUD Matrix

Irwin/McGraw-H...
SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition

Whitten Bentley Dittman

8.31 Process to Location Association Matrix

Irw...
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  1. 1. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman C H A P T E R 8 Irwin/McGraw-Hill PROCESS MODELING Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  2. 2. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Chapter Eight • • • • • • • • • • • • Whitten Bentley Dittman Process Modeling Define systems modeling and differentiate between logical and physical system models. 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. Construct a context diagram to illustrate a system’s interfaces with its work environment. Identify use cases, external and temporal business events for a system. Perform event partitioning and organize events in a functional decomposition diagram. Draw event diagrams and merge those events into a system diagram. Draw primitive data flow diagrams and describe the elementary data flows and processes in terms of data structures and procedural logic (Structured English and decision tables), respectively. Document the distribution of processes to locations. Synchronize data and process models using a CRUD matrix. Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  3. 3. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Chapter Map Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  4. 4. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Models: Logical and Physical A model is a representation of reality. Just as a picture is worth a thousand words, most models are pictorial representations of reality. Logical models show what a system is or does. They are implementation independent; that is, they depict the system independent of any technical implementation. Irwin/McGraw-Hill Physical models show not only what a system is or does, but also how the system is (to be) physically and technically implemented. They are implementation dependent because they reflect technology choices. Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  5. 5. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Why Logical System Models • Logical models remove biases that are the result of the way the system is currently implemented, or the way that any one person thinks the system might be implemented. • Logical models reduce the risk of missing business requirements because we are too preoccupied with technical results. • Logical models allow us to communicate with endusers in nontechnical or less technical languages. Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  6. 6. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman 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
  7. 7. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Simple Data Flow Diagram Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  8. 8. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Differences Between DFDs and Flowcharts • Processes on DFDs can operate in parallel (at-thesame-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
  9. 9. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman 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
  10. 10. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Process Concepts A process is work performed on, or in response to, incoming data flows or conditions. A P ro c e s s A System is a Process in p u t in p u t in p u t The S y s te m is a P ro c e s s o u tp u t o u tp u t o u tp u t Feedack and C o n tro l L o o p T h e S y s t e m 's E n v ir o n m e n t (c o n s ta n tly c h a n g in g ) Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  11. 11. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman 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 System Decomposition Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  12. 12. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Decomposition Diagrams A decomposition diagram or hierarchy chart shows the topdown, functional decomposition of a system. Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  13. 13. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman 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
  14. 14. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Common Process Errors on DFDs Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  15. 15. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Problems with Natural English PROBLEMS WITH NATURAL ENGLISH 1 • 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 Source: Adapted from Matthies, Leslie, The New Playscript Procedure, (Stamford, Companies. All Rights reserved Copyright © 2000 The McGraw-Hill CT: Office Publications, Inc. 1977)
  16. 16. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman 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. 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 $100.00 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. Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  17. 17. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Structured English Constructs (Part 1) Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  18. 18. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Structured English Constructs (Part 2) complex logic in which rows represent conditions Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  19. 19. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Structured English Constructs (Part 3) Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  20. 20. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman 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
  21. 21. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman A Simple Decision Table Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  22. 22. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Data Flows & Control Flows • A data flow represents an input of data to a process, or the output of data from a process. – A data flow may also be used to represent the creation, reading, deletion, or updating of data in a file or database (called a data store). – A composite data flow is a data flow that consists of other data flows. • A control flow represents a condition or nondata event that triggers a process. – Used sparingly on DFDs. Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  23. 23. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Data Flow Packet Concept Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  24. 24. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Composite and Elementary Data Flows Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  25. 25. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Data Flows to and from Data Stores Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  26. 26. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Illegal Data Flows Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  27. 27. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Data Structures Data flows can be defined by data structures. A data structure is a specific arrangement of data attributes that defines the organization of data contained in a data flow. A data attribute is the smallest piece of data that has meaning to the end-users of a business. Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  28. 28. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman A Data Structure for a Data Flow DATA STRUCTURE ORDER= ORDER NUMBER + ORDER DATE+ [ PERSONAL CUSTOMER NUMBER, CORPORATE ACCOUNT NUMBER]+ SHIPPING ADDRESS=ADDRESS+ (BILLING ADDRESS=ADDRESS)+ 1 {PRODUCT NUMBER+ PRODUCT DESCRIPTION+ QUANTITY ORDERED+ PRODUCT PRICE+ PRODUCT PRICE SOURCE+ EXTENDED PRICE } N+ SUM OF EXTENDED PRICES+ PREPAID AMOUNT+ (CREDIT CARD NUMBER+EXPIRATION DATE) (QUOTE NUMBER) ADDRESS= (POST OFFICE BOX NUMBER)+ STREET ADDRESS+ CITY+ [STATE, MUNICIPALITY]+ (COUNTRY)+ POSTAL CODE Irwin/McGraw-Hill ENGLISH ENTERPRETATION An instance of ORDER consists of: ORDER NUMBER and ORDER DATE and Either PERSONAL CUSTOMER NUMBER or CORPORATE ACCOUNT NUMBER and SHIPPING ADDRESS (which is equivalent to ADDRESS) and optionally: BILLING ADDRESS (which is equivalent to ADDRESS) and one or more instances of: PRODUCT NUMBER and PRODUCT DESCRIPTION and QUANTITY ORDERED and PRODUCT PRICE and PRODUCT PRICE SOURCE and EXTENDED PRICE and SUM OF EXTENDED PRICES and PREPAID AMOUNT and optionally: both CREDIT CARD NUMBER and EXPIRATION DATE An instance of ADDRESS consists of: optionally: POST OFFICE BOX NUMBER and STREET ADDRESS and CITY and Either STATE or MUNICIPALITY and optionally: COUNTRY and POSTAL CODE Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  29. 29. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Data Structure Constructs Data Structure Format by Example (relevant portion is boldfaced) English Interpretation (relevant portion is boldfaced) Sequence of Attributes - The WAGE AND TAX STATEMENT= An instance of WAGE AND TAX STATEMENTS sequence data structure indicates one TAXPAYER IDENTIFICATION NUMBER+ consists of: or more attributes that may (or must) TAXPAYER NAME+ TAXPAYER IDENTIFICATION NUMBER and be included in a data flow. TAXPAYER ADDRESS+ TAXPAYER NAME and WAGES, TIPS, AND COMPENSATION+ TAXPAYER ADDRESS and FEDERAL TAX WITHHELD+… WAGES, TIPS AND COMPENSATION and FEDERAL TAX WITHHELD and… Selection of Attributes - The ORDER= selection data structure allows you to (PERSONAL CUSTOMER NUMBER, show situations where different sets CORPORATE ACCOUNT NUMBER)+ of attributes describe different ORDER DATE+… instances of the data flow. An instance or ORDER consists of: Either PERSONAL CUSTOMER NUMBER or CORPORATE ACCOUNT NUMBER; and ORDER DATE and… Repetition of Attributes - The CLAIM= repetition data structure is used to set POLICY NUMBER+ off a data attribute or group of data POLICYHOLDER NAME+ attributes that may (or must) repeat POLICY HOLDER ADDRESS+ themselves a specific number of time 0 {DEPENDENT NAME+ for a single instance of the data flow. DEPENDENT’S RELATIONSHIP} N+ The minimum number of repetitions 1 {EXPENSE DESCRIPTION+ is usually zero or one. SERVICE PROVIDER+ The maximum number of EXPENSE AMOUNT} N repetitions may be specified as “n” meaning “many” where the actual number of instances varies for each instance of the data flow. An instance of CLAIM consists of: POLICY NUMBER and POLICYHOLDER NAME and POLICYHOLDER ADDRESS and zero or more instance of: DEPENDENT NAME and DEPENDENT’S RELATIONSHIP and one or more instances of: EXPENSE DESCRIPTION and SERVICE PROVIDER and EXPENSE ACCOUNT Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  30. 30. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Data Structure Constructs (concluded) Data Structure Format by Example (relevant portion is boldfaced) English Interpretation (relevant portion is boldfaced) Optional Attributes - The optional CLAIM= notation indicates that an attribute, or POLICY NUMBER+ group of attributes in a sequence or POLICYHOLDER NAME+ selection date structure may not be POLICYHOLDER ADDRESS+ included in all instances of a data ( SPOUSE NAME+ flow. DATE OF BIRTH)+… Note: For the repetition data structure, a minimum of “zero” is the same as making the entire repeating group “optional.” An instance of CLAIM consists of: POLICY NUMBER and POLICYHOLDER NAME and POLICYHOLDER ADDRESS and optionally, SPOUSE NAME and DATE OF BIRTH and... Reusable Attributes - For groups of DATE= attributes that are contained in many MONTH+ data flows, it is desirable to create a DAY+ separate data structure that can be YEAR+ reused in other data structures. Then, the reusable structures can be included in other data flow structures as follows: ORDER=ORDER NUMBER…+DATE INVOICE=INVOICE NUMBER…+DATE PAYMENT=CUSTOMER NUMBER…+DATE Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  31. 31. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Data Types and Domains Data attributes should be defined by data types and domains. A data type defines what class of data can be stored in an attribute (e.g., character, integers, real numbers, dates, pictures, etc.). A domain defines what values or range of values an attribute can legitimately take on. Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  32. 32. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Diverging and Converging Data Flows • A diverging data flow is one that splits into multiple data flows. – Useful for illustrating data that starts out naturally as one flow, but needs to be routed to parallel processes. – Also useful for illustrating multiple copies of the same output going to different destinations. • A converging data flow is the merger of multiple data flows into a single packet. – Useful for illustrating data from multiple sources that must come back together for some subsequent processing Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  33. 33. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Diverging and Converging Data Flows Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  34. 34. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman External Agents • An external agent defines a person, organization unit, or other organization that lies outside of the scope of the project but that interacts with the system being studied. – External agents define the “boundary” or scope of a system being modeled. – As scope changes, external agents can become processes, and vice versa. – Almost always one of the following: External Agent • Office, department, division inside the business but outside the system scope. • An external organization or agency. • Another business or another information system. • One of your system’s end-users or managers Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  35. 35. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Data Stores • A data store is an inventory of data. – Frequently implemented as a file or database. – A data store is “data at rest” compared to a data flow that is “data in motion.” – Almost always one of the following: • Persons (or groups of persons) • Places • Objects • Events (about which data is captured) • Concepts (about which data is important) Data Store – Data stores depicted on a DFD store all instances of data entities (depicted on an ERD) Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  36. 36. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman When to Draw Process Models • Strategic systems planning – Enterprise process models illustrate important business functions. • Business process redesign – “As is” process models facilitate critical analysis. – “To be” process models facilitate improvement. • Systems analysis (primary focus of this course) – Model the existing system including its limitations – Model the target system’s logical requirements (meaning processes and data flows needed regardless of how the system will be implemented) – Model candidate technical solutions (physical DFDs only) – Model the target technical solution (physical DFDs only) Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  37. 37. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Classical Structured Analysis 1. Draw top-down physical DFDs that represent the current physical implementation of the system including its limitations. 2. Convert the physical DFDs to their logical equivalents. 3. Draw top-down logical DFDs that represent an improved system. 4. Describe all data flows, data stores, policies, and procedures in a data dictionary or encyclopedia. 5. Optionally, mark up copies of the logical DFDs to represent alternative physical solutions. 6. Draw top-down physical DFDs that represent the target solution. THE ABOVE METHODOLOGY IS RARELY PRACTICED ANYMORE BECAUSE IT IS VERY CUMBERSOME AND TIME-CONSUMING. Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  38. 38. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Modern Structured Analysis 1. Draw a context DFD to establish initial project scope. 2. Draw a functional decomposition diagram to partition the system into subsystems. 3. Create an event-response or use-case list for the system to define events for which the system must have a response. 4. Draw an event DFD (or event handler) for each event. 5. Merge event DFDs into a system diagram (or, for larger systems, subsystem diagrams). 6. Draw detailed, primitive DFDs for the more complex event handlers. 7. Document data flows and processes in the data dictionary. THE ABOVE METHODOLOGY, BASED ON EVENT PARTITIONING, IS MORE COMMONLY PRACTICED. Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  39. 39. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Structured Analysis Diagram Progression Irwin/McGraw-Hill (1 of 3) Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  40. 40. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Structured Analysis Diagram Progression Irwin/McGraw-Hill (2 of 3) Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  41. 41. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Structured Analysis Diagram Progression Irwin/McGraw-Hill (3 of 3) Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  42. 42. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman CASE for DFDs (Sample Screen) Irwin/McGraw-Hill from System Architect 2001 Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  43. 43. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman SoundStage Context DFD Accounts Receivable Promotion Club Member Member Order Member Credit Status Warehouse Potential Member various Inquiry Reponses New Subscription Subscription Offer Member Services System Revised Packing Order New Promotion Subscription Program various Sales Reports Subscription Renewal various Promotion Reports Marketing Department various Subscription Reports Past Member Resubscription Offer various Member Reports Irwin/McGraw-Hill Member Services Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  44. 44. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman SoundStage Functional Decomposition Diagram Member Services System Subscription Subsystem Promotion Subsystem Order Subsystem Operations Subsystem Process Subscription Transactions Process Promotion Transactions Process Order Transactions Process Membership Transactions Generate Subscription Reports Generate Promotion Reports Generate Order Reports Process Marketing Transactions Process Warehouse Transactions Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  45. 45. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Events • Events define processes needed to respond to those events. – External events are those initiated by external agents. They result in an input transaction or data flow. – Temporal events are those that are triggered by the passage of time. They simply “happen” and are indicated by a control flow. – State events are those based on a system’s change from one state to another. Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  46. 46. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Use Cases • Use cases are based upon object-oriented concepts that are essentially the same as events. – Use case analysis is the process of identifying and modeling business events and how the system responds to them. – An actor is anything that needs to interact with the system (essentially, a synonym for external agent). Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  47. 47. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Use Case List Actor Event (or Use Case) Trigger Responses Marketing Establishes a new membership subscription plan to entice new members. NEW MEMBER SUBSCRIPTION PROGRAM Generate SUBSCRIPTION PLAN CONFIRMATION. Create AGREEMENT in the database. Marketing Establishes a new membership resubscription plan to lure back former members. PAST MEMBER RESUBSCRIPTION PROGRAM Generate SUBSCRIPTION PLAN CONFIRMATION. Create AGREEMENT in the database. Marketing Changes a subscription plan for current members (e.g., extending the fulfillment period) SUBSCRIPTION PLAN CHANGE. Generate AGREEMENT A subscription plan expires. (current date) (time) CHANGE CONFIRMATION. Update AGREEMENT in the database. Generate AGREEMENT CHANGE CONFIRMATION. Logically Delete (void) AGREEMENT in the database. Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  48. 48. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Use Case List (continued) Actor Event (or Use Case) Marketing Cancels a subscription plan before its planned expiration Trigger Responses Generate CANCELATION CHANGE CONFIRMATION. Logically Delete (void) AGREEMENT in the database. Member Joins the club by subscribing. (“Take any 12 CDs for one penny and agree to buy 4 more at regular prices within two years.”) NEW SUBSCRIPTION Generate MEMBER DIRECTORY UPDATE CONFIRMATION. Create MEMBER in the database. Create first MEMBER ORDER MEMBER ORDERED PRODUCTs in the database. Member hanges address (including email and privacy code) CHANGE OF ADDRESS Generate MEMBER DIRECTORY UPDATE CONFIRMATION. Update MEMBER in the database. Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  49. 49. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Use Case List (continued) Actor Event (or Use Case) Trigger Responses Accounts Receivable Changes member’s credit status CHANGE OF CREDIT STATUS Generate CREDIT DIRECTORY UPDATE CONFIRMATION. Update MEMBER in the database. (time) 90 days after a Marketing decides to no longer sell a product. (current date) Generate CATALOG CHANGE CONFIRMATION. Logically Delete (deactivate) PRODUCT in the database. Member Wants to pick products for possible purcase. (Logical requirement is driven by vision of web-based access PRODUCT INQUIRY Generate CATALOG DESCRIPTION. Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  50. 50. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Event Decomposition Diagram (partial) Member Services System Subscription Subsystem Process Subscription Transactions Generate Subscription Reports Promotion Subsystem Process Promotion Transactions Generate Promotion Reports Order Subsystem Process Order Transactions Generate Order Reports Process Membership Transactions Pg 3 Pg 2 Process Marketing Transactions Process Warehouse Transactions Pg 4 Generate Quarterly Subscription Report Process New Subscription Plan Operations Subsystem Generate Inactive Member Report Generate Agreement Compliance Report Generate Membership Directory Generate Subscription Analysis Report Process New Resubscription Plan Process Change to a Subscription Plan Process Subscription Plan Expiration Process Subscription Plan Cancelation Process New Member Subscription Irwin/McGraw-Hill Process Former Member Resubscription Process Member Change of Address Process Member Change of Preferences Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  51. 51. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman External Event DFD Club Member Member Change of Address Process Member Address Change Updated Member Address Members Member Updated Address Confirmation Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  52. 52. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman External Event DFD (more complex) Members Updated Member from Order Accounts Receivable Relevant Transactions Member Club Member Member Order Process Member Order Member Order Confirmation Member Orders Member Ordered Products Irwin/McGraw-Hill New Member Order New Member Ordered Products Warehouse Packing Order Inventory Commitment Product and Availability Products Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  53. 53. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Temporal Event DFD Agreements Members Fulfillment Progress Calendar End of Month Irwin/McGraw-Hill Agreement Identify Agreements Near Default Agreement Default Exception Report Agreements Manager Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  54. 54. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition System DFD Whitten Bentley Dittman (see book for more readable copy) Transactions Product and Availability Products Product and Availability Relevant Transactions Member Member Order Process Member Order Inventory Commitment Inventory Commitmen t Member Subscription Order Warehouse Packing Order Process Subscription Order Packing Order Member Order Confirmation Subscription Order Confirmation New Member Ordered Products Member Updated Member from Order Members New Member Order New Member Ordered Products Address New Member Order Members Member Orders Member Ordered Products Member Orders Deleted Member Order Orders Updated Member Updated Member Order Updated Member from Updated Order Member Order Change Request Deleted Member Ordered Products Ordered Products Member Member Order Confirmation Process Member Order Revision Generate Order Analysis Report Process Member Order Cancelation Updated Member Ordered Products Product and Availability Member Order Cancelation Member Member Order Cancelation Notice End of Day Inventory Commitment Revised Packing Order Warehouse Time Order Analysis Report Club Directors Products Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  55. 55. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Primitive DFD (see book for more readable copy) Member ID and Address Member Validate Member Members Updated Member from Order Invalid Member ID Invalid Product ID Invalid Order Ordered Product ID Validate Ordered Product Product Valid Product Ordered Product Quantity Member Member Order Check Product Availability Products Product Availability Inventory Comittment Available Product Bonus Credits Claimed Product Price Calculate Order Cost Cost to Member Payment Credit Problem and Instruction Relevant Transactions Order to be Filled Member Orders Member Ordered Products Members Irwin/McGraw-Hill Credit Details Check Member Credit Confirmed Member Order New Member Order New Member Ordered Products Transactions Order to be Filled Record Order Release Order Packing Order Warehouse Updated Credits Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  56. 56. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Data Structure for a Primitive Data Flow Data Flow Data Structure Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  57. 57. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman Logic for a Primitive Process Process Logic Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  58. 58. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman 8.30 Data to Process CRUD Matrix Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved
  59. 59. SYSTEMS ANALYSIS AND DESIGN METHODS 5th Edition Whitten Bentley Dittman 8.31 Process to Location Association Matrix Irwin/McGraw-Hill Copyright © 2000 The McGraw-Hill Companies. All Rights reserved

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