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Entity Modeling

Entity Modeling. Pratt & Adamski, Ch 6. Design Methodology Data Modeling. The Pratt and Adamski approach is not a standard MIS view. CS Start with reports and forms Identify attributes Identify tables Normalize . MIS Approach Start with a narrative description Identify entities

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Entity Modeling

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  1. Entity Modeling Pratt & Adamski, Ch 6

  2. Design Methodology Data Modeling The Pratt and Adamski approach is not a standard MIS view.

  3. CS Start with reports and forms Identify attributes Identify tables Normalize MIS Approach Start with a narrative description Identify entities Design table structure Check for normalization Data Modeling

  4. MIS Data Modeling • Top-down approach Begins with a model of the firm • Focuses on tables and relationships Begins by modeling entities and adds attributes later • Normalization used as a confirmation rather than design tool

  5. Life Cycle • Enterprise Design: major components Entities and relationships in context • Conceptual Design: business needs Tables and attributes independent of DBMS • Physical Design: technology design Entities, attributes, constraints, associative tables, etc. as they will be built

  6. 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

  7. Enterprise Model Customer SalesRep Order Product Supplier

  8. 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.

  9. Conceptual Model Customer CustomerID (PK) Name Address SalesRep SalesRepID (PK) Name Address Product ProductNum (PK) Description Price Category Order OrderNumber (PK) Date

  10. 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.

  11. Relational Model Customer CustomerID (PK) SalesRepID (FK) Name Address SalesRep SalesRepID (PK) Name Address Product ProductNum (PK) Description Price Category Order OrderNumber (PK) CustomerID (FK) Date Order-Product ProdNum (PK/FK) OrderNum (PK/FK)

  12. Entity Modeling • Represent each entity as a table • Determine the attributes for each entity • Determine the relationships among the entities

  13. Definition: Schema Notation • TableName( {attributes} ) • Primary keys are underlined or denoted “PK” • Alternate keys are denoted “AK” • Secondary keys are denoted “SK” • Foreign keys are denoted “FK” Faculty(FacID, Name, Office, Dept (FK))

  14. Table Name Primary Key (PK) Attributes (FK, SK) Attributes E-R Diagrams (P&A notation) Entities

  15. E-R Diagrams (P&A notation) • Relationships: 1 to many 1 m Department Employee Department Employee

  16. E-R Diagrams (P&A notation) • Relationships: many to many m n Student Class Student Class

  17. Data Modeling

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