Room 3 of 10
Name the connections
Our question
What happened when Maria placed Order #9821?
Back at Harbor Coffee
On September 15 at 10:15, Maria bought a latte and a muffin. Person places Order and Order contains Product are named relationships. A line with no name leaves its meaning open to interpretation.
Cardinality asks how many can participate in a connection. One product per order contradicts this purchase. Order Placed is an event: the occurrence of placing an order. The order continues to exist after that event. A transaction records an agreed unit of activity; decide what begins and completes it.
Try a modeling decision
How many products must this order be able to contain?
Choose a view to see what it makes visible.
On the whiteboard
- Purpose → What happened when Maria placed Order #9821?
Read the worked explanation
Allow one or more products. Customer places Order and Person hands over Order connect the same kinds of things with different meanings. An action may later deserve an event record with time and participants; grammar alone does not decide the model.
Room not yet explored. Capstone progress is separate.
Inspect the source
Order #9821
Supplied recordsupportedOn September 15 at 10:15, Maria ordered a latte and a muffin.
Contents of one purchase. No waiting-time measurement was supplied.
Name the concept
Relationship: A named connection between things, such as Person places Order.
Cardinality: How many instances can participate in a relationship: one, several, or none where the rules allow it.
Event / transaction: An event is an occurrence, such as Order Placed. A transaction records an agreed unit of activity; its boundary and completion need a definition.