03Conceptual_Data_Modeling1 - Database Management...

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Database Management Conceptual Data Modeling Entity Relationship Diagrams Chapter 3
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Data Management – Spring 2005 Semester “Deliverables” Planning : - Enterprise Data Model - Function vs. Entity – Class Matrix Analysis/Conceptual Design: - ER Diagrams for user views - Integrate views into Conceptual Data Model Logical Model: - 3NF relations from CDM to create the logical data model Physical Design: - Data Volume and Usage info Physical Implementation - Individual SQL problems - DDL/DML statements to create database
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Data Management – Spring 2005 ER Models “Show Me the Money” The “Gestalt” Create a conceptual data model (CDM) independent of physical implementation considerations Provide a detailed model of the data required and the relationships among the data
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Data Management – Spring 2005 Sample E-R Diagram FIGURE 3-1 Key ENTITY Relationship Sends SUPPLIER SHIPMENT Includes Supplies ITEM Used_in PRODUCT Requests CUSTOMER Submits ORDER Cardinalities Mandatory One Mandatory Many Optional One Optional Many
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Data Management – Spring 2005 Analysis and Design Steps 1. User View “Hunt” – Capture all of the user (i.e., reports, forms, screens, “stickies”, etc. 2. Separate ERDs – Create an individual ERD for each of the user views captured - Capture every attribute - Capture every relationship and business rule 3. Integrate Separate ERDs to Create CDM – Merge all the user views ERDs into a single, integrated conceptual data model (CDM) – must account for redundancy, homonyms, synonyms
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Data Management – Spring 2005 Entities (Figures 3-2, 3-5) Entity – person, place, object, event, concept, etc., of which we will record data Entity class – type or entity (depends on semantics) Entity instance – an actual occurrence Strong – instance exists without instance in related entity Weak – instance requires instance in related entity - ID dependent weak entity
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Data Management – Spring 2005 Basic E-R Notation FIGURE 3-2 Basic symbols Strong Entity Weak Entity Relationship Identifying Relationship Associative Entity Attribute Multivalued attribute Derived attribute Relationship degree Unary Binary Ternary Relationship cardinality Mandatory one Mandatory many Optional one Optional many
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Data Management – Spring 2005 Example of a weak entity FIGURE 3-5 EMPLOYEE DEPENDENT First_Name Middle_Initial Last_Name Employee_ID Employee_Name Dependent_Name Date_of_Birth Has
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