Week 1 - Databasae

What is database application program?

A database application program is a computer program that interacts with the database by issuing an appropriate request (typically an SQL statement) to the DBMS. Users interact with the database through a number of database application programs that are used to create and maintain the database and to generate information.

What is database?

A database is a large collection of interrelated data. A database is a structured collection of logically related data stored on a computer medium. A database is a mechanised, shared, formally defined and centrally controlled collection of data used in an organisation.

What is data abstraction?

A major purpose of a database system is to provide users with an abstract view of data. That is, the system hides certain details of how the data are stored and maintained. Since many database systems users are not compute trained, developers hide the complexity (i.e. complex data structures) from users through several levels of abstraction, to simplify users' interactions with the system.

What is DBA?

DBA stands for database administrator. The DBA is one of the people involded in DBMS environment and is responsible for the physical realisation of the database including physical database design and implementation, security and integrity control, maintenance of the operational system, and ensuring satisfactory performance of the application for users.

What is DBMS?

DBMS stands for Database Management System. A DBMS is a software system that enables users to define, create, maintain, and control access to the database. DBMS consists of a database and a set of programs to access the data. The primary goal of a DBMS is to provide an environment that is both convenient and efficient to define, store, and retrieve the information contained in the database.

What is metadata?

Data about data. Data that describes the structure and the properties of the data. Metadata is essential for the proper understanding and use of the data.

What is data?

Data are the collection of facts represented by numbers, text, figures, grapgics, images, audio/video recordings etc that are recorded and can be accessed. Data is recorded and kept because it is considered to be useful to an intended user.

What is data model?

Data model is a collection of conceptual tools for describing data, data relationships, data semantics, and consistency constraints.

What is database instance?

Database change over time as information is inserted and deleted. The collection of information stored in the database at a particular moment is called an instance of the database

What is database metadata?

Database metadata represents structure of the database. Database metadata includes names of the data structures, data types, data descriptions, and any other information describing the characteristics of the data.

What is file-processing system?

File-processing system is a past system for managing information. It is supported by a conventional operating system. Feature 1: The information is stored in permanent system files. Feature 2: A number of independent application programs are written to manipulate the files.

State the difference between frontend and backend of the DBMS.

Frontend of a DBMS is the part of the DBMS that interfaces with the user. Backend of a DBMS is the part of the DBMS that manages and controls access to the database.

What is information?

Information refers to the data that is accessed by an user for any particular purpose. The processed data is called information.

Describe object-based logical models.

Object-based logical models are used in describing data at the logical and view levels. They provide fairly flexible structuring capabilities. They allow data constraints to be specified explicitly. Examples: The entity-relationship model, The object-oriented model, The semantic data model, The functional data model.

State the difference between logical data independence and physical data independence.

Physical data independence is the ability to modify the physical schema without causing application programs to be rewritten. Modifications at the physical level are occasionally necessary to improve performance. Logical data independence is the ability to modify the logical schema without causing application programs to be rewritten. Modifications at the logical level are necessary whenever the logical structure of the database is altered. Logical data independence is more difficult to achieve than is physical data independence, since application programs are heavily dependent on the logical structure of the data that they access.

Describe physical data models

Physical data models are used to describe data at the lowest level. They capture aspects of database-system implementation. Examples: The unifying model, The frame-memory model.

Describe record-based logical models.

Record-based logical models are used in describing data at the logical and view levels. They are used to specify the overall logical structure of the database. They are used to provide a higher-level description of the implementation. The database is structured in fixed-format records of several types. Each record type defines a fixed number of fields, or attributes, and each field is usually of a fixed length. The use of fixed-length records simplifies the physical-level implementation of the database. Examples: The relational model, The network model, The hierarchical model.

What is data independence?

The ability to modify a schema definition in one level without affecting a schema definition in the next higher level is called data independence.

What is data administrator?

The data administrator (DA) is one of the people involved in DBMS environment and is responsible for the management of the data resource including database planning, development and maintenance of standards, policies and procedures, and conceptual/logical database design.

What is ANSI/SPARC model?

The generalized architecture of a database system called the ANSI/SPARC model. A large number of commercial systems and research database models fit this framework. The architecture is divided into three levels: (1) Physical or Internal level, (2) Logical or Conceptual or Global level, and (3) View or External or User level.ANSI: American National Standards Institute.SPARC: Standards Planning and Requirements Committee.

Describe the ANSI/SPARC Three-Level Architecture.(3) View or External or User level

The highest level of abstraction describes only part of the entire database of concern to a user or application program. The system may provide many views for the same database.

Describe the ANSI/SPARC Three-Level Architecture.(1) Physical or Internal level

The lowest level of abstraction describes how the data are actually stored. Complex low-level data structures and access methods are described in detail.

Describe the ANSI/SPARC Three-Level Architecture.(2) Logical or Conceptual or Global level

The middle level describes what data are stored in the database, and what relationships exist among those data. The entire database is described in terms of a small number of relatively simple structures.

What is database schema?

The overall design of the database is called the database schema. Database systems have several schemas, partitioned according to the levels of abstraction. At the lowest level is the physical schema; at the intermediate level is the logical schema; at the highest level is the subschema. In general, database systems support one physical schema, one logical schema, and several subschemas.

What is database system?

The term database system is used to define a collection of application programs that interact with the database. A database system is designed to manage large bodies of information. The management of data involves - (i) the definition of structures for the storage of information and (ii) the provision of mechanisms for the manipulation of information. The system must provide for the satety of the information stored, despite system crashes or attempts at unauthorised access. If data are to shared among several users, the system must avoid possible anomalous results.

What are the major components of the DBMS environment?

There are five major components in the DBMS environment: hardware, software, data, procedures and people.

Classify DBMS people.

There are four distinct types of people that participate in the DBMS environment: data and DB administrators, DB designers, application developers and end-users.