Database Data is one of the most critical assets of any business. It is used and collected practically everywhere, from businesses trying to determine consumer patterns based on credit card usage, to space agencies trying to collect data from other planets. Data, as important as it is, needs robust, secure, and highly available software that can store and process it quickly. The answer to these requirements is a solid and a reliable database. Database software usage is pervasive, yet it is taken for granted by the billions of daily users worldwide. Its presence is everywhere-from retrieving money through an automatic teller machine to badging access at a secure office location. 35836
What is a database?Since its advent, databases have been among the most researched knowledge domains in computer science. A database is a repository of data, designed to support efficient data storage, retrieval and maintenance. Multiple types of databases exist to suit various industry requirements. A database may be specialized to store binary files, documents, images, videos, relational data, multidimensional data, transactional data, analytic data, or geographic data to name a few.Data can be stored in various forms, namely tabular, hierarchical and graphical forms. If data is stored in a tabular form then it is called a relational database. When data is organized in a tree structure form, it is called a hierarchical database. Data stored as graphs representing relationships between objects is referred to as a network database. In this book, we focus on relational databases.
What is a database management system?While a database is a repository of data, a database management system,or simply DBMS, is a set of software tools that control access, organize, store, manage, retrieve and maintain data in a database. In practical use, the terms database, database server,database system, data server, and database management systems are often used interchangeably.Why do we need database software or a DBMS? Can we not just store data in simple text files for example? The answer lies in the way users access the data and the handle of corresponding challenges. First, we need the ability to have multiple users insert, update and delete data to the same data file without "stepping on each other's toes". This means that different users will not cause the data to become inconsistent, and no data should be inadvertently lost through these operations. We also need to have a standard interface for data access, tools for data backup, data restore and recovery, and a way to handle other challenges such as the capability to work with huge volumes of data and users. Database software has been designed to handle all of these challenges.The most mature database systems in production are relational database management systems (RDBMS’s). RDBMS's serve as the backbone of applications in many industries including banking, transportation, health, and so on. The advent of Web-based interfaces has only increased the volume and breadth of use of RDBMS, which serve as the data repositories behind essentially most online commerce.
An information model is an abstract, formal representation of entities that includes their properties, relationships and the operations that can be performed on them. The entities being modeled may be from the real world, such as devices on a network, or they may themselves be abstract, such as the entities used in a billing system.
The primary motivation behind the concept is to formalize the description of a problem domain without constraining how that description will be mapped to an actual implementation in software. There may be many mappings of the Information Model. Such mappings are called data models, irrespective of whether they are object models (forexample, using unified modeling language - UML), entity relationship models, or XML schemas.
Modeling is important as it considers the flexibility required for possible future changes without significantly affecting usage. Modeling allows for compatibility with its predecessor models and has provisions for future extensions. 数据库英文文献和中文翻译:http://www.youerw.com/fanyi/lunwen_33977.html