Interpret a Data Flow Diagram - Exercise

Objective: Identify a data store and trace the arrows in a data flow diagram.

Read the diagram

This small legacy excerpt uses Yourdon/DeMarco notation. Squares are external entities, a circle is a process, parallel lines are a data store, and arrows show data movement. Its process is labeled “Order”; a fuller diagram would use a verb phrase and label the flows and store.

Clerk sends data to the Order process, which sends data to Vendor and down to an unlabeled data store — Read the arrowheads; the diagram does not specify execution timing.

What do the parallel lines between Vendor and Clerk represent? State what their contents could be and what the excerpt leaves unspecified.
In one sentence, trace the flow from Clerk through Order to both destinations. Do not invent a sequence between the two output arrows.

Self-assessment: 20 points

Question 1: 5 points for identifying a data store, 3 for a plausible order-related interpretation, and 2 for noting that its exact contents/storage technology are unspecified. Question 2: 4 points for Clerk to Order, 4 for both outputs (Vendor and data store), and 2 for not inventing an output sequence. This is a self-assessment; the page displays a model answer and does not grade free text.

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