Ch02_Summary - INFS 428 January 17, 2012 Summary Notes...

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INFS 428 January 17, 2012 Summary Notes Chapter 2 Modeling Data in the Organization Associative entity: An entity type that associates the instances of one or more entity types and contains attributes that are peculiar to the relationship between those entity instances Entity-relationship diagram (E-R diagram ): a graphical representation of an entity- relationship model Relationship instance : an association between or among entity instances where each relationship instance associates exactly one entity instance from each participating entity type Attribute : A property or characteristic of an entity type that is of interest to the organization Relationship type: A meaningful association between (or among) entity types Binary relationship : a relationship between the instances of two entity Entity-relationship model (E-R model ): A logical representation of the data for an organization or for a business area Required attribute : an attribute that must have a value for every entity instance with which it is associated Business rule : A statement that defines or constrains some aspect of the business Simple (or atomic) attribute : an attribute that cannot be broken down into smaller components that are meaningful to the organization Cardinality constraint: Specifies the number of instances of one entity that can (or must) be associated with each instance of another entity Fact : an association between two or more terms Strong entity type : an entity that exists independently of other entity types Composite attribute : an attribute that has meaningful component parts Identifier : An attribute (or combination of attributes) that uniquely identifies individual instances of an entity type Term : a word or phrase that has a specific meaning for the organization Composite identifier : an identifier that consists of a composite attribute Identifying owner : the entity type on which the weak entity depends Ternary relationship : a simultaneous relationship among instances of three entity types
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Ch02_Summary - INFS 428 January 17, 2012 Summary Notes...

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