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Published byRalph Potter Modified over 9 years ago
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Entity Modeling Pratt & Adamski, Ch 6
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The Pratt and Adamski approach is not a standard MIS view. Design Methodology Data Modeling
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CS zStart with reports and forms zIdentify attributes zIdentify tables zNormalize MIS Approach z Start with a narrative description z Identify entities z Design table structure z Check for normalization
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MIS Data Modeling zTop-down approach Begins with a model of the firm zFocuses on tables and relationships Begins by modeling entities and adds attributes later zNormalization used as a confirmation rather than design tool
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Life Cycle zEnterprise Design: major components Entities and relationships in context zConceptual Design: business needs Tables and attributes independent of DBMS zPhysical Design: technology design Entities, attributes, constraints, associative tables, etc. as they will be built
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Enterprise Design Determine the entities and relationships that interact with the proposed system. Don’t model attributes, constraints or tables necessary to implement relational structures or sub-classes
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SalesRep Order Customer Supplier Product Enterprise Model
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Conceptual Design Determine the model of the system independent of the DBMS that will be used for physical implementation. System entities, primary keys, attributes, relationships, constraints. No associative entities, foreign keys or sub-classes.
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SalesRep SalesRepID (PK) Name Address Order OrderNumber (PK) Date Customer CustomerID (PK) Name Address Product ProductNum (PK) Description Price Category Conceptual Model
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Relational and Physical Design Produce a detailed model of the ultimate system. Model a complete normalized system. Then denormalize selectively to improve the operational characteristics of the final database.
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SalesRep SalesRepID (PK) Name Address Order OrderNumber (PK) CustomerID (FK) Date Customer CustomerID (PK) SalesRepID (FK) Name Address Product ProductNum (PK) Description Price Category Relational Model Order-Product ProdNum (PK/FK) OrderNum (PK/FK)
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Entity Modeling zRepresent each entity as a table zDetermine the attributes for each entity zDetermine the relationships among the entities
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Definition: Schema Notation zTableName( {attributes} ) yPrimary keys are underlined or denoted “PK” yAlternate keys are denoted “AK” ySecondary keys are denoted “SK” yForeign keys are denoted “FK” Faculty(FacID, Name, Office, Dept (FK))
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E-R Diagrams (P&A notation) Entities Primary Key (PK) Attributes (FK, SK) Attributes Table Name
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E-R Diagrams (P&A notation) zRelationships: 1 to many DepartmentEmployee 1m DepartmentEmployee
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E-R Diagrams (P&A notation) zRelationships: many to many StudentClass mn Student
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Data Modeling
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