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Unformatted text preview: Topic 3: Introduction to the Relational Database Model Topic: Introduction to the Relational Database Model With the background of data / information concepts, database management systems, and early database models, we can now go into more detail on the Relational Database Model. We will discuss some of the ideas of conceptual modeling and how the logical design of an organizations data requirements is a separate but necessary precursor for any database project. We will discuss the Three-Level ANSI-SPARC Architecture, an excellent model of how to separate the users needs from the database designers and DBAs requirements. We will introduce the basic terminology of the Relational Database Model. Finally, we will go into a brief overview of some of the mathematical foundations for the Relational Model. Though much of this is hidden by the RDBMS, it is important to understand what is going on behind the curtain when problems arise. After reading this topic, you should be able to: Discuss the Three-Level ANSI-SPARC Architecture Describe the terminology of the Relational Database Model Lesson 1: The Three-level ANSI-SPARC Architecture Information is the output of the data that is input into any collection system from file folder to database. Users are normally not interested in how the data is stored and managed. They are very interested in how to obtain it and make informed decisions. This separation of the external viewpoint from the internal physical organization is an important concept to remember throughout the entire database development process. One of the best ways to understand this is to review a model of database architectures called the Three-Level ANSI-SPARC Architecture. It is a bit difficult to grasp with a limited understanding of database concepts, but it is something you can refer back to as you go through the course. After reading this lesson, you will be able to: Describe the Three-Level ANSI-SPARC Architecture Define what is meant by the External level or user view of data Define the Conceptual Schema level Define the Internal Schema level of data History and Objectives of the Three-Level Architecture With some of the early work on database models, an attempt was made to try and apply standards to the database design process and the creation of system catalogs describing the database. In 1975, the American National Standards Institute (ANSI) Standards Planning and Requirements Committee (SPARC) created a proposed standard for database models. It identifies three distinct levels at which data items can be described. The levels form a three-level architecture comprising an external, a conceptual, and an internal level. The objective of the three-level architecture is to separate each user's view of the database from the way it is physically presented. Graphic based on Connoly, T. and Begg, C.. Database Systems: A Practical Approach to Design, Implementation, and Management (4th ed.), P.35 Figure 2.1. Addison Graphic based on Connoly, T....
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- Summer '08