Review Questions

The four symbols on a data flow diagram are:

•Rounded rectangles (processes) •Squares (external agents) •Open-ended boxes (data stores) •Arrows (data flows)

What are the four symbols on a data flow diagram?

DepositDataStore

Pay a billProcess No.

ExternalAgent

Review Questions

Processes describe only one business activity. Every process must have at least one input data flow and must produce at least one output data flow. Generally, there is no reason for a process to exist if no outputs are produced, and at least one input is required in order to produce output

Every process must have several things. What are they and why?

Review Questions

Process decomposition is when a system is separated into its component subsystems, which in turn are decomposed into smaller subsystems, until such a time as we have identified manageable subsets of the overall system

In process modeling, decomposition allows you to partition a system into logical subsets of processes for improved communication, analysis, and design

What is process decomposition and what role does it play in process modelling?

Review Questions

The parent process for 3.2.1 is process 3.2.

What is the parent process for process 3.2.1? 4.3.2.3? And 1.2?

The parent process for 4.3.2.3 is process 4.3.2.The parent process for 1.2 is process 1.

Decomposition Diagrams

A decomposition diagram or hierarchy chart shows the top-down, functional decomposition of a system.

Review Questions

A syntax error is an error in the data flow diagrams that is the result of violating the rules of data flow diagramming, much like a grammatical error. A semantics error is an error of meaning in the data flow diagram, in which the model does not accurately represent the business process being modeled.

Semantic errors are harder to detect because a good understanding of the business system is required to find them and fix them.

Explain the difference between a syntax error and a semantics error. Which is usually the most difficult to find and fix? Why?

Review Questions

Review Questions

What are some guidelines for designing a Context data flow diagram?

• Start by placing a single process symbol in the center of the page. The symbol represents the entire information system, and you identify it as process 0

• Then place the external agents around the perimeter of the page and use data flows to connect the entities to the central process

• Do not show any data stores in a context diagram because data stores are internal to the system

• Place the external agents around the central process and label them

• Create labeled input and output data flows between the external agents and the central system

Review Questions

Review Questions

What are some guidelines for designing a diagram 0?

• A context diagram provides the most general view of an information system

• Diagram 0 zoom in on the context diagram and shows major processes, data flows and data stores.

• Each process in diagram 0 has a reference number.

• Diagram 0 also represents the external agents and data flows that appear in the context diagram

Review Questions

Review Questions

What is balancing?Balancing involves assuring that all the information from a higher-level diagram is appropriately represented on the next level, or 'child' diagram. The child diagram shows more detail, but must show all the inflows and outflows to and from the parent process on the higher level diagram

Review Questions

What is balancing?

Review Questions

What is the relationship between a context diagram and diagram 0, and which symbol is not used in a context diagram?

The context diagram contains only one process symbol, process 0, which represents the entire system. Diagram 0 is a more detailed version of process 0 on the context diagram. The major processes, data flows, and data stores for the information system are shown on diagram 0.

The data store symbol is not used in a context diagram. Use a data store only when two or more processes use that data store. Otherwise, the data store is internal to a process, and not visible from the outside. Because a context diagram involves only one process, all data stores are internal to that process and do not appear in the context diagram

Review Questions

The purpose of the plant science information system is to document the study results from a wide variety of experiments performed on selected plants. A study is initiated by a researcher who submits a research proposal. After a panel review by a group of scientists, the researcher is required to submit a research plan and schedule. A FDA research permit request is sent to the Food and Drug Administration, which sends back a research permit. As the experiment progresses, the researcher fills out and submits experiment notes. At the conclusion of the project, the researcher’s results are reported on an experiment histogram. Draw a context data flow diagram

PLANT SCIENCE

Information

SYSTEM

RESEARCHER

Food and

ADMINISTRATION

Research Proposal

Experiment Histogram

Research Plan & Schedule

FDA Permit Request

Research permit

Experiment Notes

Review Questions

A Video Store (AVS) runs a series of fairly standard video stores. Before a video can be put on the shelf, it must be catalogued and entered into the video database. Every CUSTOMER must have a valid AVS customer card to rent a video. CUSTOMERS rent videos for 3 days at a time. Every time a CUSTOMER rents a video, the system must ensure that he or she does not have any overdue videos. If so, the overdue videos must be returned and an overdue fee must be paid before the customer can rent more videos. Likewise, if the customer has returned overdue videos but has not paid the overdue fee, the fee must be paid before new videos can be rented. Every morning the store MANGER prints a report that lists overdue videos; if a video is 2 or more days overdue, the manager calls the customer to remind him or her to return the video. If a video is returned in damage condition, the manager removes it from the video database and may sometimes charge the customer. SUPPLIER provides video descriptive information to the system.

VideoDescriptiveInformation

Damaged Video Information

Customer information

Video to rent

Overdue Video Notice

Customer AVS

System

SupplierVideo to return

Manager

Review QuestionsVideo DescriptiveInformation

New videoinformation

D1 Videos

Video removedfrom stock

Videoinformation

Damaged videoinformation

Customer information

AVS Customer card

Overdue video fee

Overdue video payment

D2 Customers

Overdue fee paymentOverduevideofee

Customerinformation

Supplier Maintain Inventory

1

Manager

Maintain Video Rentals

3

Customer

CustomerMaintain customer data

2

Customer data

Overdue video fee

Overdue video assessment

D3 Video Rentals

Returned VideoRented VideoRented information

Overdue video notice

AVS Card

Video to rent

Video to return

One more example of context diagram

One more example of diagram 0

Yesterday Lecture

• Process: is an organised set of activities which transforms inputs to outputs

• Data flow: A path for data to move from one part of the system to another

• Data store: Represents data that is retained for later processing

• External entity/agent: Represents a person, organization, or other system that provides data or receives output from the system

• Context data flow diagram: Top-level view that shows the systems’ boundaries and scope

• Diagram 0: Diagram 0 zoom in on the context diagram and shows major processes, data flows and data stores