Context Diagram This section includes two parts. Part 1: Description of a Context Diagram Part 2: How To construct a Context Diagram.

Context Diagram Part 1: Description of a Context Diagram A Context Diagram has three components: a) Process, in the form of a circle, for the system. b) External Entity, in the form of a rectangle. c) Data Flow, in the form of an arc or line.

Context Diagram Part 1: Description of a Context Diagram Process, in the form of a circle, for the system. 1)Name of the system in question, represents the encapsulation of all the data and processes necessary for the system. 2)Is named a noun or noun phrase representing the name of the entire system. 3)Can receive input and produce output Data Flows. XYZ System

Context Diagram Part 1: Description of a Context Diagram b) External Entity, in the form of a rectangle 1)Name of a person, place or thing that produces information for the system (source) or receives information from the system (sink). 2)Is named a noun or noun phrase representing the name of the source or sink. 3)Must be connected to a Data Flow. Person, Place, or Thing

Context Diagram Part 1: Description of a Context Diagram c) Data Flow, in the form of an arc or line. 1)Name of data flowing along the arc or line (either one is fine). Represents information serving as input or output of the system. 2)Is named a noun or noun phrase representing the name of the information (one element or a composition of elements). 3)Must be connected at one end to and External Entity and the other end to the main process. information

Context Diagram Part 2: How To construct a Context Diagram. To describe how to construct a Context Diagram, we will use a typical Telephone Registration System example. In this system, students call on the telephone and request registration for a class and the system then tells them their entire schedule.

Context Diagram Part 2: How To construct a Context Diagram. Step 1: Construct the Process 1a) Draw a circle in the middle of the page. 1b) Place the name of the system in the middle (noun phrase). Telephone Registration System

Context Diagram Part 2: How To construct a Context Diagram. Step 2: Construct the Data Flows 2b) Draw a line or arc(either is fine) for each input. 2c) Place the name of the input along the line or arc (noun phrase). Telephone Registration System 2a) Think of the inputs needed for this process. class request

Context Diagram Part 2: How To construct a Context Diagram. Step 2: Construct the Data Flows (con’t) 2e) Draw a line or arc(either is fine) for each output. 2f) Place the name of the output along the line or arc (noun phrase). Telephone Registration System 2d) Think of the outputs needed for this process. class request class schedule

Context Diagram Part 2: How To construct a Context Diagram. Step 3: Construct the External Entities. 3b) Draw a rectangle to represent the origination entity. 3c) Place the name of the external entity in the rectangle. Telephone Registration System 3a) Determine where the inputs originate. class request class schedule Student