A database server is a server which uses a database application that provides database services to other computer programs or to computers, as defined by the client–server model. Database management systems (DBMSs) frequently provide database-server functionality, and some database management systems (such as MySQL) rely exclusively on the client–server model for database access (while others, like SQLite, are meant for use as an embedded database). Users access a database server either through a "front end" running on the user's computerwhich displays requested dataor through the "back end", which runs on the server and handles tasks such as data analysis and storage. In a master–slave model, database master servers are central and primary locations of data while database slave servers are synchronized backups of the master acting as proxies. Most database applications respond to a query language. Each database understands its query language and converts each submitted query to server-readable form and executes it to retrieve results. Examples of proprietary database applications include Oracle, IBM Db2, Informix, and Microsoft SQL Server. Examples of free software database applications include PostgreSQL; and under the GNU General Public Licence include Ingres and MySQL. Every server uses its own query logic and structure. The SQL (Structured Query Language) query language is more or less the same on all relational database applications. For clarification, a database server is simply a server that maintains services related to clients via database applications. DB-Engines lists over 300 DBMSs in its ranking. History The foundations for modeling large sets of data were first introduced by Charles Bachman in 1969. Bachman introduced Data Structure Diagrams (DSDs) as a means to graphically represent data. DSDs provided a means to represent the relationships between different data entities. In 1970, Codd introduced the concept that users of a database should be ignorant of the "inner workings" of the database. Codd proposed the "relational view" of data which later evolved into the Relational Model which most databases use today. In 1971, the Database Task Report Group of CODASYL (the driving force behind the development of the programming language COBOL) first proposed a "data description language for describing a database, a data description language for describing that part of the data base known to a program, and a data manipulation language." Most of the research and development of databases focused on the relational model during the 1970s. In 1975, Bachman demonstrated how the relational model and