417 ACTIVITY 8: Interface Modeling Using Context Diagrams

WHY:

This activity is designed to help you learn to draw a Context Data Flow Diagram to organize and document a system's interaction with its environment. We will deal with business processes or essential vs implementation models in studying the current system. You will make much use of your diagraming skills both with your project and in your careers as systems analysts.

LEARNING OBJECTIVES:

1. Discover how to construct a Context-level Data Flow Diagrams.
2. Discover what to look for in a problem to identify external entities and essential data flows.
3. Practice using the proper language to describe external agents, processes, data flows, and data stores.

PERFORMANCE CRITERIA:

1. Quality of the answers to the Critical Thinking Questions.
   • Completeness
   • Clarity
   • Depth
2. Quality of the context-level data flow diagram created by your team

RESOURCES:

1. Chapter 6, Systems Analysis and Design Methods
2. 30 minutes

PLAN:

1. Choose roles if you have not already done so.
2. Answer the Critical Thinking Questions.
3. Work through problem 2 on page 257, drawing the context diagram.

MODEL:

See Problem 1, page 257 in the textbook. The external agents are Student, Academic Department, and Publishing Company since these are the main providers of input data and recipients of output data from the TEXTBOOK INVENTORY SYSTEM. Note that the bookstore is not an agent because the entire system takes place in the bookstore. The major inputs to the system are a TEXTBOOK MASTER LIST from an academic department, a BOOK REQUEST from a student and a PACKING SLIP from a publishing company. The major outputs are a SALES RECEIPT to a student, and a PURCHASE ORDER to a publishing company. Note that we do not try to define what goes on inside the system at this time. The Context Diagram is as follows:

   ______________
   |  Academic  |
   | Department |____________________
   |____________|Textbook Master List|
   				     |
				     |
				     |
                                 ___\|/______ 			____________
				|  Textbook  |<-----------------|          |
				|  Inventory |  Packing Slip    |Publishing|
	----------------------->|   System   |			| Company  |
	|  Book Request		|____________|----------------->|__________|
	|			      |	        Purchase Order
	|			      |
	|			      |
  ______|_____			      |
  |          |			      |
  | Student  |<-----------------------|
  |__________|    Sales Receipt

CRITICAL THINKING QUESTIONS:

These will be provided in class.

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