MISY330 Lecture 2: Video 1 - An Introduction to Entity-Relationship Modeling

• School: University of Delaware
• Department: Management Information Systems
• Course: MISY330
• Professor: Serva Mark

Document Summary

Components of an er model: boxes that represent entities, each entity can include multiple types of data, cardinalities, minimum cardinality at minimum, an entity must participate this many times in the relationship. If the minimum cardinality is a 1 (i. e. , one and only one ), the entity is a mandatory participant. Order a customer doesn"t have to place an order, but can place many orders. A left arrow ( < ) in the middle of the line connecting two entities will indicate to read the relationship from right to left instead of the assumed left to right. Adding the dimension of time complicates cardinalities i. e. , the relationship between a car and its owners becomes more complicated when it becomes the relationship between a car and all of its previous owners. Visio: use basic diagram and drag in the basic shapes then use the connector tool. Come up with the cardinalities for these relationships.