blm352ENACh02final_sham

blm352ENACh02final_sham - Copyright 2007 Ramez Elmasri and...

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Slide 2- 1 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe
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Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Chapter 2 Database System Concepts and Architecture
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Slide 2- 3 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Outline Data Models and Their Categories History of Data Models Schemas, Instances, and States Three-Schema Architecture Data Independence DBMS Languages and Interfaces Database System Utilities and Tools Centralized and Client-Server Architectures Classification of DBMSs
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Slide 2- 4 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Data Models Data Model: A set of concepts to describe the structure of a database, the operations for manipulating these structures, and certain constraints that the database should obey. Data Model Structure and Constraints: Constructs are used to define the database structure Constructs typically include elements (and their data types ) as well as groups of elements (e.g. entity, record, table ), and relationships among such groups Constraints specify some restrictions on valid data; these constraints must be enforced at all times
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Slide 2- 5 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Data Models (continued) Data Model Operations: These operations are used for specifying database retrievals and updates by referring to the constructs of the data model. Operations on the data model may include basic model operations (e.g. generic insert, delete, update) and user-defined operations (e.g. compute_student_gpa, update_inventory)
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Slide 2- 6 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Categories of Data Models Conceptual (high-level, semantic) data models: Provide concepts that are close to the way many users perceive data. (Also called entity-based or object-based data models.) Physical (low-level, internal) data models: Provide concepts that describe details of how data is stored in the computer. These are usually specified in an ad-hoc manner through DBMS design and administration manuals Implementation (representational) data models: Provide concepts that fall between the above two, used by many commercial DBMS implementations (e.g. relational data models used in many commercial systems).
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Slide 2- 7 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Schemas versus Instances Database Schema: The description of a database. Includes descriptions of the database structure, data types, and the constraints on the database. Schema Diagram: An illustrative display of (most aspects of) a database schema. Schema Construct: A component of the schema or an object within the schema, e.g., STUDENT, COURSE.
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Slide 2- 8 Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe Schemas versus Instances Database State: The actual data stored in a database at a particular moment in time . This includes the collection of all the data in the database. Also called database instance (or occurrence or
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This note was uploaded on 03/21/2010 for the course CS 145 taught by Professor Markjan during the Spring '10 term at Abilene Christian University.

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blm352ENACh02final_sham - Copyright 2007 Ramez Elmasri and...

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