Analysis Systems and Design, Sixth Edition
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Systems Analysis and Design
Sixth Edition
Instructor's Manual
CHAPTER FOUR
Data and Process Modeling
LESSON PLAN
OBJECTIVES
When students finish this chapter, they will be able to: Describe data and process modeling concepts and tools, including data flow diagrams, a data dictionary, and process descriptions Describe the symbols used in data flow diagrams and explain the rules for their use Draw data flow diagrams in a sequence, from general to specific Explain how to level and balance a set of data flow diagrams Describe how a data dictionary is used and what it contains Use process description tools, including structured English, decision tables, and decision trees Describe the relationship between logical and physical models
INSTRUCTOR NOTES
Introduction, 146 LECTURE NOTES Define data and process modeling. Compare data and process modeling to the requirements modeling process described in Chapter 3. Differentiate between a logical model and a physical model. A logical model shows what a system must do without committing to a technology. This allows a development team to focus on what is needed instead of what form it will take. For example, a logical model could specify output as a list of data, without committing to a specific format. A physical model would include details about the format. Usually, systems analysis requires creating detailed logical models, while systems design requires physical models. List the four main tools involved in enterprise modeling. Preview what students will learn in Chapter 5. Present the Chapter Introduction Case: Mountain View College Bookstore on page 147. This introduction case sets up the material developed in the chapter. Review the background, participants, project status, and discussion topics for the case. Discuss Figure 4-1. CLASSROOM ACTIVITIES Consider assigning students to each role in the Chapter Introduction Case: Mountain View College Bookstore on page 147 and having them enact the case dialogue.
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Overview of data and process modeling tools, 148 LECTURE NOTES Define data flow diagram (DFD). Unlike an entity-relationship diagram (ERD), which is described in Chapter 7, which shows the data needed by a system, including items about which information is stored and the relationships among them, a DFD shows inputs, processes, storage, and outputs of a system. Refer students to Part 2 of the Systems Analyst's Toolkit for explanation of how to document business functions and processes, develop graphical models, and provide an overall framework for information system development. QUICK QUIZZES Assign Review Question 1 on page 183. Data flow diagrams, 148 LECTURE NOTES Note that the Systems Analyst's Toolkit explains how to use visual aids to present a concept. Discuss Figure 4-2. Remind students what a data flow diagram shows. A DFD represents system requirements as processes, external entities, data flows, and data stores. Emphasize that a DFD shows what a system does, not how it does it. Mention why the distinction is important. DFD symbols, 148 LECTURE NOTES Because DFDs are graphical models that use a limited number of symbols, with minimal training they can be read and interpreted by information system workers, end users, and management, making them a valuable tool for communication. List the four components represented in a DFD. Point out that several versions of DFD symbols exist. Use Figure 4-3 to illustrate the Gane and Sarson symbol set and the Yourdon symbol set. The Gane and Sarson symbol set is used in this textbook. Explain how symbols are referenced. CLASSROOM ACTIVITIES Point out On the Web, and encourage students to use scsite.com/sad6e/more for more information about Yourdon symbols. PROJECTS TO ASSIGN Assign Project 4 on page 183. Process symbol, 148 LECTURE NOTES Define process. A process can be a procedure or an algorithm. Point out that processes can be simple or complex. List examples of processes. Define business logic, or business rules. Use Figure 4-3 to describe the symbol for a process. Tell how a process is named. Note that processing details are not shown in a DFD. Define black box. Discuss Figure 4-4. DISCUSSION TOPICS Assign Discussion Topic 4 on page 183.
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Data flow symbol, 149 LECTURE NOTES Define data flow. Data flows represent data movement among processes, data stores, and external entities. Point out that a DFD does not show the structure and content of a data flow. Use Figure 4-3 to describe the symbol for a data flow. Tell how a data flow is named. Use Figure 4-5 to show correct examples of data flow and process symbols. Point out that a process can have more than one outgoing data flow or more than one incoming data flow. Emphasize that a process symbol must have at least one data flow. Use Figure 4-6 to show examples of incorrect combinations of data flows and processes -- processes with no input data flows, processes with no output data flows, and processes with an input data flow insufficient to generate the output data flow. Define spontaneous generation process, black hole process, and gray hole process. Because data emerges without any apparent source, some analysts refer to a spontaneous generation process as a miracle. Explain why spontaneous generation, black holes, and gray holes are logically impossible in a DFD. CLASSROOM ACTIVITIES Encourage students to invent other creative examples of spontaneous generation, black holes, and gray holes. Data store symbol, 151 LECTURE NOTES Define data store. A data store represents a file or part of a database. Suggest examples of data stores. Point out that a DFD does not show detailed contents of a data store, and explain why the physical characteristics of a data flow are unimportant. Use Figure 4-3 to describe the symbol for a data store. Tell how data stores are named. Emphasize that a data store must be connected to a process with a data flow, and usually a data store must have at least one incoming and one outgoing data flow. Discuss Figure 4-7. Use Figure 4-8 to illustrate examples of incorrect uses of data store symbols. Note the exception to the requirement that a data store must have an incoming and outgoing data flow. Entity symbol, 153 LECTURE NOTES Use Figure 4-3 to describe the symbol for an entity. Recall the definition of entity a person, place, thing, or event for which data is collected and maintained. An external entity (sometimes called external agent) is outside the system boundary but supplies input or accepts output. List examples of entities. Note that a DFD shows the boundaries of a system and how it interfaces with the outside world. Define terminators. Differentiate between a source and a sink. Tell how an entity is named. Emphasize that an entity must be connected to a process by a data flow. Use Figures 4-9 and 4-10 to illustrate correct and incorrect uses of external entities in DFDs. Use Figure 4-11 to summarize rules for using DFD symbols. QUICK QUIZZES Assign Review Question 2 on page 183.
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Chapter 4, Enterprise Modeling
Creating a set of DFDs, 154 LECTURE NOTES Review the three information systems that will be used to teach the construction of DFDs. Review the three main tasks involved in creating a set of DFDs. Draw a context diagram, 155 LECTURE NOTES Define context diagram. A context diagram is the most abstract, least detailed, model. A context diagram symbolizes all processing activity within a system with a single process symbol. Tell how to draw a context diagram. Explain why data stores are not shown. Mention how to determine which entities and data flows are shown in a context diagram. Context diagram example, 155 LECTURE NOTES Discuss Figures 4-12, 4-13, and 4-14. Explain what makes one system more complex than another. Drawing guidelines, 156 LECTURE NOTES Review the guidelines for drawing context diagrams. The stipulation that a DFD should have no more than nine process symbols sometimes is called the rule of 7 2. This rule derives from psychological research that indicates most people can remember between 5 and 9 pieces of information at a time. A larger number leads to difficulty in understanding as a result of information overload. In addition to having no more than nine process symbols, the rule of 7 2 suggests that no more than nine data flows should enter or leave a process, data store, or entity on a single DFD. CLASSROOM ACTIVITIES If possible, present students with a series of context diagrams that violate the guidelines listed on pages 156 through 158 and ask them to identify what the problem is with each diagram. Draw a diagram 0 DFD, 158 LECTURE NOTES Describe diagram 0. Some analysts call diagram 0 an event-partitioned system model. Diagram 0 shows the details of process 0 in the context diagram. Using Figure 4-15, compare the context diagram and diagram 0 for the grading system. In Figure 4-15, diagram 0 shows the details of process 0 (GRADING SYSTEM) in the context diagram. Point out that all of the connections that flow into and out of process 0 are retained in diagram 0. Explain why the reference numbers for each process in diagram 0 are important. Emphasize that the process numbers do not suggest that processes are accomplished in a sequential order. Describe a diverging data flow. Point out the diverging data flow in diagram 0 in Figure 4-15. Tell how to indicate that data flows in both directions. Define exploded view. Differentiate between the parent diagram and the child diagram. Define functional primitive. Explain how systems analysts decide whether to explode a process further. Discuss Figure 4-16. Walkthrough the DFD shown in Figure 4-16. Unlike the processes in Figure 4-15, some of the processes in Figure 4-16 are not functional primitives and need more detailed description.
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PROJECTS TO ASSIGN Assign Project 1 on page 183. QUICK QUIZZES Assign Review Questions 3 and 4 on page 183. Draw the lower-level diagrams, 160 LECTURE NOTES Define leveling and balancing. Point out that leveling and balancing are used to create lowerlevel diagrams. Leveling, 160 LECTURE NOTES Describe leveling, also called exploding, partitioning, or decomposing. Explain how an analyst uses leveling. Use Figure 4-16 to illustrate an example of leveling for process 1 (FILL ORDER) in the diagram 0 DFD shown in Figure 4-16. Point out how processes are numbered in Figure 417. Tell how DFDs for processes that are decomposed further would be labeled. Explain why a child DFD (Figure 4-17) may contain data stores not shown in the parent DFD (Figure 4-16). Explain why analysts often use this technique and how the missing entities can be identified. CLASSROOM ACTIVITIES Compare Figure 4-18 with Figure 4-17 and ask students how the diagrams are different (two entities CUSTOMER and WAREHOUSE are missing in Figure 4-18). QUICK QUIZZES Assign Review Question 6 on page 183.
CASE IN POINT 4.1: BIG TEN UNIVERSITY
You are the IT director at Big Ten University. As part of a training program, you decide to draw a DFD that includes some obvious mistakes to see whether your newly hired junior analysts can find them. You came up with the diagram 0 DFD shown in Figure 4-19. Based on the rules explained in this chapter, how many problems should the analysts find? Comments: The DFD is presented as diagram 0, and it should follow the rules presented in the text. Some of the errors include the following: ASSIGN ADVISOR, process 1, is a miracle. CHECK OPEN CLASSES, process 3 is a black hole. CALCULATE GRADE, process 4 is a gray hole. Also, INSTRUCTOR and STUDENT external entities cannot be connected with a data flow. INSTRUCTOR entity does not connect to a process. GRADES and SEATING CHART data stores are black holes. CLASS ROSTER and SEATING CHART data stores cannot be connected with a data flow.
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Balancing, 164 LECTURE NOTES Describe balancing. Using Figure 4-20, explain why the parent diagram (top) and the child diagram (bottom) are balanced. Have students find each input and output data flow for process 3 in the parent diagram and in the child diagram. Point out that balancing can be verified by counting the data flows to and from external entities for the process in the parent diagram and making sure that the same number of data flows to and from external entities in the child diagram is the same. In other words, in diagram 0 shown at the top of Figure 4-20, process 3 (APPLY PAYMENT) has one incoming data flow from an external entity (CUSTOMER) and three outgoing data flows to external entities (SALES DEPT., BANK, and ACCOUNTINGS). In diagram 3 shown at the bottom of Figure 4-20, there is one incoming data flow from an external entity (CUSTOMER) and three outgoing data flows to external entities (BANK, ACCOUNTING, and SALES REP.). Use Figures 4-21 and 4-22 to show another example of balancing, created with a popular CASE tool. Discuss Figures 4-23 and 4-24. CLASSROOM ACTIVITIES Ask students how they can tell the DFDs in Figures 4-20 and 4-21 are balanced and leveled. PROJECTS TO ASSIGN Assign Project 2 on page 183. QUICK QUIZZES Assign Review Question 7 on page 183. Data dictionary, 167 LECTURE NOTES Point out that DFDs show a logical model of a system but not the details. Describe a data dictionary, or data repository. Define data element (also called a data item or field) and records (or data structures). Discuss Figure 4-25. CLASSROOM ACTIVITIES Point out On the Web, and encourage students to use scsite.com/sad6e/more for more information about data dictionaries. QUICK QUIZZES Assign Review Question 5 on page 183. Documenting the data elements, 168 LECTURE NOTES Emphasize that every data element must be documented in the data dictionary. Mention different ways that analysts record their notes. Discuss Figures 4-26 and 4-27. List the attributes usually recorded for each data element in the data dictionary. Define alias, type, length, domain, and validity rules.
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Documenting the data flows, 169 LECTURE NOTES Emphasize that all data flows must be documented in the data dictionary. Use Figure 4-28 to show documentation for a data flow. List the typical attributes recorded for a data flow. Documenting the data stores, 170 LECTURE NOTES Emphasize that every DFD data store must be documented in the data dictionary. Use Figure 429 to show documentation for a data store. List the typical characteristics of a data store. Documenting the processes, 171 LECTURE NOTES Emphasize that every process must be documented in the data dictionary. Discuss Figure 4-30. Mention what is included in the documentation. List typical characteristics of a process. Documenting the entities, 171 LECTURE NOTES Use Figure 4-31 to explain how entities are documented. List typical characteristics of an entity. Documenting the records, 172 LECTURE NOTES Recall the meaning of record. Use Figure 4-32 to show how characteristics of a record are defined. List typical characteristics of a record. Data dictionary reports, 172 LECTURE NOTES Point out that a data dictionary documents not only components of an information system, but also relationships between the components. List valuable reports that can be obtained from a data dictionary. Process description tools, 173 LECTURE NOTES Define process description. typical List process description tools. Explain how modular design is used. Modular design, 173 LECTURE NOTES Define modular design and logical structures, or control structures. Logical structures determine the logical order of steps in a process. Point out that logical structures have only one entry point and one exit point. List the three logical structures. Note how modular design represents a step or process, a condition or decision, and the flow of logic. Use Figure 4-33 to define sequence structure. Use Figure 4-34 to define selection structure. Two common types of selection structures are if-then-else and case. The if-then-else structure yields one of two possibilities. The case structure can yield three or more possibilities. Use Figure 4-35 to define iteration (or looping) structure. Two forms of iteration structures are do-while and do-until. The do-while structure tests a condition at the beginning of the loop and repeats as long as the
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condition is true. The do-until structure tests a condition at the end of the loop and repeats until the condition is true -- and then stops. Point out that sequence, selection, and iteration structures can be combined to describe processing logic. CLASSROOM ACTIVITIES Encourage students to draw a diagram similar to Figure 4-33 to show how the sequence structure might be applied to an everyday task. For example:
Put on socks
Put on shoes
Tie shoes
Have students draw a diagram similar to Figure 4-34 to show how the selection structure might be applied to an everyday task. For example:
Temperature < 60
YES
Put on a jacket NO
Have students draw a diagram similar to Figure 4-35 to show how the iteration structure might be applied to an everyday task. For example:
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Hole in sock?
YES
Change sock
NO
Structured English, 173 LECTURE NOTES Define structured English. Structured English uses brief statements to describe a process carefully. List the rules for structured English. Discuss Figure 4-36. Explain how structured English is similar to, and different from, pseudocode. Discuss Figure 4-37. Structured English is good for describing processes with many sequential processing steps and fairly simple logic. Structured English is not good for describing processes with complex decision logic and few (or no) sequential steps. CLASSROOM ACTIVITIES Point out On the Web, and encourage students to use scsite.com/sad6e/more for more information about structured English. QUICK QUIZZES Assign Review Question 10 on page 183. Decision tables, 175 LECTURE NOTES Define decision table. Explain how analysts use decision tables. A decision table quantifies decisions in response to various input conditions. Discuss Figure 4-38. Review the steps to create a decision table. Some people feel that decision tables summarize decision logic more clearly than structured English. There is a predictable relationship between the number of conditions in a decision and the number of possible outcomes. As the number of conditions increases, the complexity of the outcomes grows geometrically. Sometimes, however, certain conditions preclude others, so fewer rules are necessary. Use Figure 4-39 to illustrate decision tables for a more complex situation. Point out how the first table is simplified by eliminating duplicate rules and combining rules. Note that decision tables can have more than two possible outcomes. Discuss Figure 4-40. Mention why analysts and programmers use decision tables. CLASSROOM ACTIVITIES Point out On the Web, and encourage students to use scsite.com/sad6e/more for more information about decision tables. Have students generate a decision table that can be used for a simple decision, such as
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determining whether to wear a heavy jacket, light jacket, or no jacket depending on outside temperature (less than 60 or less than 40) and precipitation. The decision table might look something like this:
Rules 1 Conditions: Temp < 60? Temp < 40? Precipitation? Actions: No jacket Light jacket Heavy jacket N N N X X X X X X 2 N N Y 3 Y N N 4 Y N Y 5 Y Y N 6 Y Y Y
Sometimes, certain conditions preclude others, so fewer rules are necessary. For example, in the decision table above if the temperature is less than 40, it has to be less than 60. When students generate their decision tables, have them identify conditions that preclude other conditions. PROJECTS TO ASSIGN Assign Project 3 on page 183. DISCUSSION TOPICS Ask students which summarizes the VERIFY ORDER process more clearly -- the structured English in Figure 4-36 or the decision table in Figure 4-38. Why? QUICK QUIZZES Assign Review Question 8 on page 183.
CASE IN POINT 4.2: ROCK SOLID OUTFITTERS (PART 1)
Leah Jones is the IT manager at Rock Solid Outfitters, a medium-sized supplier of outdoor climbing and camping gear. Steve Allen, the marketing director, has asked Leah to develop a special Web-based promotion. As Steve described it to Leah, Rock Solid will provide free shipping for any customer who either completes an online survey form or signs up for the Rock Solid online newsletter. Additionally, if a customer completes the survey and signs up for the newsletter, Rock Solid will provide a $10 merchandise credit for orders over $100. Leah has asked you to develop a decision table that will reflect the promotional rules that a programmer will use. She wants you to show all possibilities, then to simplify the results to eliminate any combinations that would be unrealistic or redundant. Comments: Step 1: Design the table with three possible conditions and two possible outcomes. The three separate conditions should produce a total of eight possible rules, and the table should look something like the following example:
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CASE IN POINT 4.2: ROCK SOLID OUTFITTERS (PART 1)
RULES Completed survey form? Signed up for newsletter? Order > $100? Free shipping Discount 1 Y Y Y X X 2 Y Y N X 3 Y N Y X 4 Y N N X 5 N Y Y X 6 N Y N X 7 N N Y 8 N N N -
Step 2: Now the rules can be simplified, by considering the following: a. If a customer completes the survey form AND signs up for the newsletter, as in Rules 1 and 2, then he or she is eligible for the discount IF the order is over $100. Therefore, two separate rules are involved, and the third condition (order amount) is relevant. b. If a customer completes the survey form OR signs up for the newsletter, as in Rules 3, 4, 5, and 6, he or she will get free shipping, but the amount of the order does not matter. Therefore, these cases can be considered as two separate rules, where one of the conditions is met, but not the other. c. If a customer does not fulfill either one of the conditions, as in Rules 7 and 8, he or she does not receive either free shipping or a discount, so the order amount is irrelevant. This can be treated as a single rule. The following table shows the simplification just described: RULES Completed survey form? Signed up for newsletter? Order > $100? Free shipping Discount 1 Y Y Y X X 2 Y Y N X 3 Y N X 4 Y N X 5 N Y X 6 N Y X 7 N N 8 N N -
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CASE IN POINT 4.2: ROCK SOLID OUTFITTERS (PART 1)
Step 3: Finally, based on the analysis described in Step 2, the original eight rules can be combined into just five rules, as follows: RULES Completed survey form? Signed up for newsletter? Order > $100? Free shipping Discount 1 Y Y Y X X 2 Y Y N X 3 Y N X 4 N Y X 5 N N -
Decision trees, 177 LECTURE NOTES Describe a decision tree. Discuss Figure 4-41. Point out that decision trees and decision tables are considered equivalent. Compare the decision tree in Figure 4-42 to the decision table in Figure 4-40. When a decision tree is drawn, the conditions in the decision table become the horizontal branches in the decision tree. Consider how to decide whether a decision table or a decision tree is the more appropriate choice. CLASSROOM ACTIVITIES Challenge students to generate a decision tree from the decision table they constructed earlier. For example, a decision tree for the CHOOSE JACKET process might look something like this:
< 40 Y < 60 N
Y N
Heavy jacket Light jacket Y N Light jacket No jacket
Precip?
Systems Analysis and Design, Sixth Edition DISCUSSION TOPICS Assign Discussion Topic 2 on page 183. QUICK QUIZZES Assign Review Question 9 on page 183.
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CASE IN POINT 4.3: ROCK SOLID OUTFITTERS (PART 2)
Leah Jones, the IT manager at Rock Solid Outfitters, thinks you did a good job on the decision table task she assigned to you. Now she wants you to use the same data to develop a decision tree that will show all the possibilities for the Web-based promotion described in Part 1 of the case. She also wants you to discuss the pros and cons of decisions tables versus decision trees. Comments: Decision trees and decision tables provide the same results, but in different forms. As the chapter points out, a decision tree is a graphical representation of the same conditions, actions, and rules found in a decision table. Decision trees show the logic structure in a horizontal form that resembles a tree with the roots at the left and the branches to the right. Like flowcharts, decision trees are useful ways to present the system to management. In many situations, a graphic is the most effective means of communication. Like a decision table, a decision tree illustrates the action to be taken based on certain conditions, but presents it graphically. Whether to use a decision table or a decision tree often is a matter of personal preference. A decision table might be a better way to handle complex combinations of conditions. On the other hand, a decision tree is an effective way to describe a relatively simple process.
Logical versus physical models, 178 LECTURE NOTES Explain how a physical model is different from a logical model. Tell when a physical model is created. Sequence of models, 178 LECTURE NOTES Explain the relationship between logical and physical models. Mention that many systems analysts create a physical model of the current system, then develop a logical model of the current system, and then develop a logical model of the new system. Four-model approach, 178 LECTURE NOTES Define four-model approach. Consider the advantages of the four-model approach. Point out the lone disadvantage of the four-model approach. The four-model approach can be compared to the carpenter's dictum, "measure twice, cut once" -- although it requires additional time and effort, it ensures desired results.
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CASE IN POINT 4.4: TIP TOP STAFFING
Tip Top Staffing supplies employees to hundreds of IT firms that require specialized skills for specific projects. Systems analysts Lisa Nuevo and Bill Goodman are working on the logical model of Tip Top's billing and records system, using DFDs, a data dictionary, and process descriptions. At some point while working on the logical model of the system, Lisa felt that some improvements should be made in the data forms that Tip Top uses to obtain information about job applicants. Was the subject of improving the forms a physical implementation issue? Is Lisa going off on a tangent by considering how something will be done, instead of sticking to what will be done? Comments: Students should understand the difference between logical and physical design. Point out that the four-model approach requires you to translate a physical situation into a logical model and then convert the logical model to a physical model for implementation. The main disadvantage of a four-model approach is the time required to follow all four steps. Students might find it easier to remember the four steps by using the acronym PHILLIP, which reminds them of PLLP -- or physical-logical-logical-physical. At this point in the systems development process, systems analysts are focusing on logical design (what is, or should be done) rather than how it will be done. Careful consideration of specific forms and procedures often provides valuable clues about the strengths and weakness of the current system, however. Turning to the Tip Top case, if Lisa was spending time on the design of a new form that would not be used until later on, she might be off on a tangent. But if she is reviewing forms to see if they reflect the scope of the new system, she is simply continuing the factfinding process. Obviously, there is considerable overlap between logical and physical design, and no strict rules exist. Ask students to suggest other examples of an overlap between logical and physical design, and remind them about the four-step process.
Chapter summary, 179 LECTURE NOTES Briefly review the material presented in this chapter. Key terms and phrases, 180 LECTURE NOTES This list presents important terms introduced in this chapter. Encourage students to use this list in preparing for tests and quizzes. Learn It Online, 181 LECTURE NOTES These exercises use the Web for additional review of the topics presented in this chapter. Have students use their browsers and the given URL (scsite.com/sad6e/learn) to complete selected exercises.
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Case-SIM: SCR Associates, 182 LECTURE NOTES This case study is a Web-based simulation that allows students to practice their skills in a realworld environment. Refer students to scsite.com/sad6e/scr for detailed instructions about the SCR Case. Chapter exercises, 183 LECTURE NOTES These exercises check student understanding of the material presented in this chapter. Have students complete the Review Questions and Discussion Topics. Assign (or allow students to select) one or more projects. Apply Your Knowledge, 184 LECTURE NOTES These exercises give students a chance to use what they have learned in this chapter in four minicases. Review and assign (or allow students to select) one or more mini-cases. Case studies, 186 LECTURE NOTES These exercises provide practical experience and allow students to work with specific skills learned in this chapter. Two of the case studies (New Century Health Clinic and Personal Trainer, Inc.) continue throughout the text. Students can be assigned one or more case studies, or allowed to choose the case studies in which they are most interested.
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KEY TERMS AND PHRASES
alias (168) balancing (160) black box (149) black hole (150) business logic (148) business rules (148) child diagram (158) context diagram (155) control structures (173) data dictionary (167) data element (167) data flow (149) data flow diagram (DFD) (148) data item (167) data repository (167) data store (151) data structures (167) decision table (175) decision tree (177) decomposing (160) diagram 0 (158) diverging data flow (158) domain (169) entity (153) exploding (160) field (167) four-model approach (178) functional primitive (159) Gane and Sarson (148) gray hole (151) iteration (173) length (168) leveling (160) logical model (146) logical structures (173) looping (173) modular design (173) parent diagram (158) partitioning (160) physical model (146) process (148) process description (173) pseudocode (174) records (167) selection (173) sequence (173) sink (153) source (153) spontaneous generation (150) structured English (173) terminators (153) type (168) validity rules (169) Yourdon (148)