Term
| entity relationship (E-R) model |
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Definition
| a logical representation of the data for an organization or for a business area, using entities for categories of data and relationships for associations between entities |
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| entity-relationship (E-R) diagram |
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Definition
| a graphical representation of an entity relationship model |
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Definition
| a statement that defines or constrains some aspect of the business. It is intended to assert business structure or to control or influence the behavior of the business |
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Definition
| a word or phrase that has a specific meaning for the business |
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Definition
| an association between two or more terms |
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Definition
| a person place or object or event or concept in the user environment about which the organization wishes to maintain data |
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Definition
| a collection of entities that share common properties or characteristics (versus an entity instance); entity type is described just once with metadata in a database |
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Definition
| a single occurrence of an entity type; many instances of an entity type may be represented by data stored in the database |
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| a entity that exists independently of other entity types |
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| an entity type whose existence depends on some other entity type |
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| an entity type on which the weak entity type depends |
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Definition
| the relationship between a weak entity type and its owner |
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Definition
| a property or characteristic of an entity or relationship type that is of interest to the organization |
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Definition
| an attribute that must have a value for every entity (or relationship) instance with which it is associated |
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Definition
| a attribute that may not have a value for every entity (or relationship) instance with which it is associated |
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Term
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Definition
| an attribute that has meaningful component parts (attributes) |
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Term
| simple (or atomic) attribute |
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Definition
| an attribute that cannot be broken down into smaller components that are meaningful to the organization |
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Definition
| an attribute that may take on more than one value for a given entity (or relationship) instance [e.g. skill] |
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Definition
| an attribute whose values can be calculated from related attribute values; [e.g. GPA]; should be avoided if possible, as it may become outdated |
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| an attribute (or combination of attributes) whose value distinguishes instances of an entity type (will brome primary key) |
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| an identifier that consists of a composite attribute |
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Definition
| meaningful association between (or among) entity types; denoted by a line labeled with the name of the relationship |
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Definition
| an association between (or among) entity instances where each relationship instance associates exactly one entity instance from each participating entity type |
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Definition
| 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 |
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Definition
| the number of entity types that participate in a relationship |
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Definition
| a relationship between instances of a single entity type |
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Definition
| a relationship between the instances of two entity types; most common |
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Definition
| a simultaneous relationship among the instances of three entity types |
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| a rule that specifies the number of instances of one entity that can (or must) be associated with each instance of another entity |
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Definition
| minimum number of instances of one entity that may be associated with each instance of another entity |
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Definition
| maximum number of instances of one entity that may be associated with each instance of another entity |
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Definition
| a time value that is associated with a data value, often indicating when some event occurred that affected the data value |
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