Friday, September 16, 2016

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.





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