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Characteristics of Things. Relationship Naturally occurring association among specific things Occur in two directions Number of associations is cardinality or multiplicity Binary, unary, ternary, n-ary Attribute One specific piece of information about a thing. - PowerPoint PPT Presentation
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Characteristics of Things• Relationship– Naturally occurring association among specific
things– Occur in two directions– Number of associations is cardinality or multiplicity• Binary, unary, ternary, n-ary
• Attribute– One specific piece of information about a thing
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Relationships Naturally Occur Between Things
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Cardinality/Multiplicity of Relationships
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Attributes and Values
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Data Entities
• Things system needs to store data about in traditional IS approach
• Modeled with entity-relationship diagram (ERD)
• Requirements model used to create the database design model for relational database
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The Entity-Relationship Diagram (ERD)
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Cardinality Symbols of Relationships for ERD
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Expanded ERD with Attributes Shown
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Customers, Orders, and Order Items
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ERD with Many-to-Many Relationship
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Many-to-Many Relationship Converted to Associative Entity to Store Grade Attribute
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RMO Customer Support System ERD
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