Database Systems - Part 3 & 4

A data model is an integrated collection of concepts fordescribing and manipulating data, relationships betweendata, and constraints on the data in an organization.• A model is a representation of “real world” objects andevents, and their associations. It is an abstraction thatconcentrates on the essential, inherent aspects of anorganization and ignores accidental properties.• A data model must provide the basic concepts and notationsthat will allow database designers and end-usersunambiguously and accurately to communicate theirunderstanding of the organizational data....
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Database Systems - Part 3 & 4 COP 4710: Database Systems Spring 2004 Introduction to Data Modeling BÀI 3&4, 2 ngàyInstructor : Mark Llewellyn markl@cs.ucf.edu CC1 211, 823-2790 http://www.cs.ucf.edu/courses/cop4710/spr2004 School of Electrical Engineering and Computer Science University of Central FloridaCOP 4710: Database Systems (Day 4) Page 1 Mark Llewellyn Data Models• A data model is an integrated collection of concepts for describing and manipulating data, relationships between data, and constraints on the data in an organization.• A model is a representation of “real world” objects and events, and their associations. It is an abstraction that concentrates on the essential, inherent aspects of an organization and ignores accidental properties.• A data model must provide the basic concepts and notations that will allow database designers and end-users unambiguously and accurately to communicate their understanding of the organizational data.COP 4710: Database Systems (Day 4) Page 2 Mark Llewellyn Data Models (cont.)• A data model can be thought of as comprising three components: 1. A structural part, consisting of a set of rules according to which databases can be constructed. 2. A manipulative part, defining the types of operations that are allowed on the data (this includes operations that are used for updating or retrieving data from the database and for changing the structure of the database). 3. Possibly a set of integrity rules, which ensures that the data is accurate.COP 4710: Database Systems (Day 4) Page 3 Mark Llewellyn Data Models (cont.)• Looking at the three level architecture, we can identify three different, related data models. 1. An external data model to represent each user’s view of the organization. 2. A conceptual data model to represent the logical (or community view) that is DBMS independent. 3. An internal data model to represent the conceptual schema in such a way that it can be understood by the DBMS.COP 4710: Database Systems (Day 4) Page 4 Mark Llewellyn Data Models (cont.)• There have been many different data models which have been theorized, utilized, developed, and implemented over the years. They fall into three broad categories: object-based, record- based, and physical.• There are three principle record-based models: the relational data model, the network data model, and the hierarchical data model. Our focus will be on the relational data model in this course.COP 4710: Database Systems (Day 4) Page 5 Mark Llewellyn Introduction to Data Modeling• Semantic data models attempt to capture the “meaning” of a database. Practically, they provide an approach for conceptual data modeling.• Over the years there have been several different semantic data models that have been proposed.• By far the most common is the entity-relationship data model, most often referred to as simply the E-R data model.• The E-R model is often used as a form of communication between database designers and the end users during the developmental stages of a database. COP 4710: Database Systems (Day 4) Page 6 Mark Llewellyn Introduction to Data Modeling (cont.)• The E-R model contains an extensive set of modeling tools, some of which we will not be concerned with as our primary objective is to give you some insight into conceptual database design and not learning all of the ins and outs of the E-R model.• Another conceptual modeling which is becoming more common is the Object Definition Language (ODL) which is an object-oriented approach to database design that is emerging as a standard for object-oriented database systems. COP 4710: Database Systems (Day 4) Page 7 Mark Llewellyn Introduction to Data Modeling (cont.)• The database design process can be divided into six basic steps. Semantic data models are most relevant to only the first three of these steps.1. Requirements Analysis: The first step in designing a database application is to understand what data is to be stored in the database, what applications must be built on top of it, and what operations are most frequent and subject to performance requirements. Often this is an informal process involving discussions with user groups and studying the current environment. Examining existing applications expected to be replaced or complemented by the database system. COP 4710: Database Systems (Day 4) Page 8 Mark Llewellyn I ...