Matrix Diagrams

• A grid-like drawing that can be used to discover and record relationships between entities in an entity- relationship model - matrix diagram

1.      Read the business scenario and review the ERD. Using the matrix diagram, make up two or more possible relationships between PHOTOGRAPH and the other entities that make sense for the business.

Scenario:

“I’m an amateur photographer. I own several cameras and am always taking pictures of different subjects. I’m trying to keep track of which camera and type of film perform best under certain conditions—indoor light, outdoor light, etc.—so when I have my films developed, I note down which camera I used. When the pictures come back, I note the subject and conditions. Each picture always features one subject. A subject could be a view, a person or group of persons, or an object or group of objects.”

Two possible relationships are:

	CAMERA	PHOTOGRAPH	SUBJECT
CAMERA		Used to take with
PHOTOGRAPH	Taken with		of
SUBJECT		Featured in

2. Complete the matrix diagram below, and construct an ERD from it.

	Runner	City For Race	Race Type	Running Event
Runner		visits	chooses	attends
City For Race	visited by			hosts
Race Type	Chosen by			Contained in
Running Event	Attended by	Happens in	contains

1.      City of race must be visited by many runners, otherwise there is no race and hence, it’s not a city of race. Runner may visit multiple city of race since he is very enthusiastic.

2.      RaceType must be chosen by many runners otherwise, racetype will be dropped from the event. Runner may wish to pick up multiple RaceTypes ,  he may be versatile.

3.      Event must be attended by multiple runners or there is no event. Runner may choose to attend multiple events.

4.      City of race must host running event/events or else it’s not a city of race. An event must happen in a city.

5.      RUNNING event must have one or more race types, runner won’t pay baseball in running event, will they run small or big distances. A racetype may be present in multiple events happening around.