tailieunhanh - Database Systems - Part 3 & 4

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 Spring 2004 Introduction to Data Modeling BÀI 3&4, 2 ngày School of Electrical Engineering and Computer Science University of Central Florida Instructor : Mark Llewellyn markl@ CC1 211, 823-2790 Phd, MS, Under 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. Data Models A data model can be thought of as comprising three components: A structural part, consisting of a set of rules | COP 4710: Database Systems Spring 2004 Introduction to Data Modeling BÀI 3&4, 2 ngày School of Electrical Engineering and Computer Science University of Central Florida Instructor : Mark Llewellyn markl@ CC1 211, 823-2790 Phd, MS, Under 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. Data Models A data model can be thought of as comprising three components: A structural part, consisting of a set of rules according to which databases can be constructed. 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). Possibly a set of integrity rules, which ensures that the data is accurate. Data Models (cont.) Looking at the three level architecture, we can identify three different, related data models. An external data model to represent each user’s view of the organization. A conceptual data model to represent the logical (or community view) that is DBMS independent. An internal data model to represent the conceptual schema in such a way that it can be understood by the DBMS. 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 .