ERNew - CSCD34 Data Management Systems A Vaisman The Entity-Relationship Model CSCD34 Data Management Systems A Vaisman Overview of Database Design

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Unformatted text preview: CSCD34- Data Management Systems. A. Vaisman The Entity-Relationship Model CSCD34- Data Management Systems. A. Vaisman Overview of Database Design Requirements Analysis: Understand what data will be stored in the database, and the operations it will be subject to. Conceptual Design : ( ER Model is used at this stage.) What are the entities and relationships in the enterprise? What information about these entities and relationships should we store in the database? What are the integrity constraints or business rules that hold? A database `schema’ in the ER Model can be represented pictorially ( ER diagrams ). Can map an ER diagram into a relational schema. Logical Design : Convert the conceptual database design into the data model underlying the DBMS chosen for the application. CSCD34- Data Management Systems. A. Vaisman Overview of Database Design (cont.) Schema Refinement : (Normalization) Check relational schema for redundancies and anomalies. Physical Database Design and Tuning : Consider typical workloads and further refinement of the database design (v.g. build indices). Application and Security Design : Consider aspects of the application beyond data. Methodologies like UML often used for addressing the complete software development cycle. CSCD34- Data Management Systems. A. Vaisman ER Model Basics Entity : Real-world object distinguishable from other objects. An entity is described using a set of attributes . Entity Set : A collection of entities of the same kind. E.g., all employees. All entities in an entity set have the same set of attributes. Each entity set has a key(a set of attributes uniquely identifying an entity) . Each attribute has a domain . Employees ssn name lot CSCD34- Data Management Systems. A. Vaisman ER Model Basics (Contd.) Relationship : Association among two or more entities. E.g., Peter works in Pharmacy department. Relationship Set : Collection of similar relationships. An n-ary relationship set R relates n entity sets E1 ... En; each relationship in R involves entities e 1 ∈ E1, ..., e n ∈ En Same entity set could participate in different relationship sets, or in different “roles” in same set. Relationship sets can also have descriptive attributes (e.g., the since attribute of Works_In). A relationship is uniquely identified by participating entities without reference to descriptive attributes....
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This note was uploaded on 05/02/2010 for the course CS 174a taught by Professor Zhin during the Fall '09 term at UCSB.

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ERNew - CSCD34 Data Management Systems A Vaisman The Entity-Relationship Model CSCD34 Data Management Systems A Vaisman Overview of Database Design

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