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                                    DATA MODELS In Short -- Data models are the collection of conceptual tools for describing data, relationships, data semantics and data constraints.  Categories of Data Models : *High Level/Conceptual Level -- Provide concepts that are close to the way many users perceive data. For example : Entity Relationship Model. *Low Level/Physical Level -- Provide concepts that describe the details of how data is stored in the computer. *Representational/Implementation Data Model -- Provide concepts that may be understood by the end users but that are not too for removed from the way data is organized with the computer. For example : Network and Hierarchical.

                    DATABASE MANAGEMENT SYSTEM (DBMS) In Short:-- A Database Management System (DBMS) is a collection of programs that enables users to create and maintain tables. The DBMS is a general purpose software system that facilitates the processes of defining, constructing, manipulating and sharing databases among various users and applications. DBMS includes :-- A modeling language to define the schema of each database hosted in the DBMS, according to the DBMS data model. Data Structures (fields, records and files) optimized to deal with very large amounts of data stored on a permanent data storage device. A database query language to allow users to interactively interrogate the database, analyze its data and update it according to the users privileges on data. A transaction machine, that ideally would guarantee the ACID properties, in order to ensure data integrity, despite concurrent user access and faults.