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Database Management System-Introduction to Computing-Handout, Exercises of Introduction to Computing

Dr. Bhim Rao Ambedkar UniversityIntroduction to Computing

This is lecture handout for Introduction to Computing course. It was provided by Prof. Neelam Kapoor at B R Ambedkar National Institute of Technology. It includes: Database, Management, System, Software, Package, Programs, Maintain, Administrators, Relational, Object, Model

Typology: Exercises

2011/2012

Uploaded on 07/19/2012

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Adatabase management system (DBMS) is a software package with computer programs that control
the creation, maintenance, and use of adatabase. It allows organizations to conveniently develop
databases for various applications by database administrators (DBAs) and other specialists.
Adatabase is an integrated collection of data records, files, and other objects. A DBMS allows different
user application programs to concurrently access the same database. DBMSs may use a variety
of database models, such as the relational model or object model, to conveniently describe and support
applications. It typically supports query languages, which are in fact high-level programming languages,
dedicated database languages that considerably simplify writing database application programs.
Database languages also simplify the database organization as well as retrieving and presenting
information from it. A DBMS provides facilities for controlling data access, enforcing data integrity,
managingconcurrency control, and recovering the database after failures and restoring it from backup
files, as well as maintaining database security.
Components
DBMS engine accepts logical requests from various other DBMS subsystems, converts them into
physical equivalents, and actually accesses the database and data dictionary as they exist on a
storage device.
Data definition subsystem helps the user create and maintain the data dictionary and define the
structure of the files in a database.
Data manipulation subsystem helps the user to add, change, and delete information in a database
and query it for valuable information. Software tools within the data manipulation subsystem are most
often the primary interface between user and the information contained in a database. It allows the
user to specify its logical information requirements.
Application generation subsystem contains facilities to help users develop transaction-intensive
applications. It usually requires that the user perform a detailed series of tasks to process a
transaction. It facilitates easy-to-use data entry screens, programming languages, and interfaces.
Data administration subsystem helps users manage the overall database environment by providing
facilities for backup and recovery, security management, query optimization, concurrency control, and
change management.
Modeling language
A modeling language is a data modeling language to define the schema of each database hosted in the
DBMS, according to the DBMS database model. Database management systems (DBMS) are designed
to use one of five database structures to provide simplistic access to information stored in databases. The
five database structures are:
the hierarchical model,
the network model,
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A database management system ( DBMS ) is a software package with computer programs that control the creation, maintenance, and use of adatabase. It allows organizations to conveniently develop databases for various applications by database administrators (DBAs) and other specialists. A database is an integrated collection of data records, files, and other objects. A DBMS allows different user application programs to concurrently access the same database. DBMSs may use a variety of database models, such as the relational model or object model, to conveniently describe and support applications. It typically supports query languages, which are in fact high-level programming languages, dedicated database languages that considerably simplify writing database application programs. Database languages also simplify the database organization as well as retrieving and presenting information from it. A DBMS provides facilities for controlling data access, enforcing data integrity, managingconcurrency control, and recovering the database after failures and restoring it from backup files, as well as maintaining database security.

Components

DBMS engine accepts logical requests from various other DBMS subsystems, converts them into physical equivalents, and actually accesses the database and data dictionary as they exist on a storage device.  Data definition subsystem helps the user create and maintain the data dictionary and define the structure of the files in a database.  Data manipulation subsystem helps the user to add, change, and delete information in a database and query it for valuable information. Software tools within the data manipulation subsystem are most often the primary interface between user and the information contained in a database. It allows the user to specify its logical information requirements.  Application generation subsystem contains facilities to help users develop transaction-intensive applications. It usually requires that the user perform a detailed series of tasks to process a transaction. It facilitates easy-to-use data entry screens, programming languages, and interfaces.  Data administration subsystem helps users manage the overall database environment by providing facilities for backup and recovery, security management, query optimization, concurrency control, and change management.

Modeling language

A modeling language is a data modeling language to define the schema of each database hosted in the DBMS, according to the DBMS database model. Database management systems (DBMS) are designed to use one of five database structures to provide simplistic access to information stored in databases. The five database structures are:  the hierarchical model,  the network model,

 the relational model,  the multidimensional model, and  the object model. Inverted lists and other methods are also used. A given database management system may provide one or more of the five models. The optimal structure depends on the natural organization of the application's data, and on the application's requirements, which include transaction rate (speed), reliability, maintainability, scalability, and cost.

The hierarchical structure

The hierarchical structure was used in early mainframe DBMS. Records’ relationships form a treelike model. This structure is simple but nonflexible because the relationship is confined to a one-to-many relationship. IBM’s IMS system and the RDM Mobile are examples of a hierarchical database system with multiple hierarchies over the same data. RDM Mobile is a newly designed embedded database for a mobile computer system. The hierarchical structure is used primarily today for storing geographic information and file systems. . A hierarchical database model is a data model in which the data is organized into a tree-like structure. The structure allows representing information using parent/child relationships: each parent can have many children, but each child has only one parent (also known as a 1-to-many relationship ). All attributes of a specific record are listed under an entity type. Example of a hierarchical model In a database an entity type is the equivalent of a table. Each individual record is represented as a row, and each attribute as a column. Entity types are related to each other using 1:N mappings, also known as one-to-many relationships. This model is recognized as the first database model created by IBM in the 1960s.

The multidimensional structure is similar to the relational model. The dimensions of the cube-like model have data relating to elements in each cell. This structure gives a spreadsheet-like view of data. This structure is easy to maintain because records are stored as fundamental attributes—in the same way they are viewed—and the structure is easy to understand. Its high performance has made it the most popular database structure when it comes to enabling online analytical processing (OLAP).

The object-oriented structure

The object-oriented structure has the ability to handle graphics, pictures, voice and text, types of data, without difficultly unlike the other database structures. This structure is popular for multimedia Web-based applications. It was designed to work with object-oriented programming languages such asJava. The dominant model in use today is the ad hoc one embedded in SQL, despite the objections of purists who believe this model is a corruption of the relational model since it violates several fundamental principles for the sake of practicality and performance. Many DBMSs also support theOpen Database Connectivity API that supports a standard way for programmers to access the DBMS. Before the database management approach, organizations relied on file processing systems to organize, store, and process data files. End users criticized file processing because the data is stored in many different files and each organized in a different way. Each file was specialized to be used with a specific application. File processing was bulky, costly and inflexible when it came to supplying needed data accurately and promptly. Data redundancy is an issue with the file processing system because the independent data files produce duplicate data so when updates were needed each separate file would need to be updated. Another issue is the lack of data integration. The data is dependent on other data to organize and store it. Lastly, there was not any consistency or standardization of the data in a file processing system which makes maintenance difficult. For these reasons, the database management approach was produced.

Hierarchical model

In the Hierarchical model different record types (representing real-world entities) are embedded in a predefined hierarchical (tree-like) structure. This hierarchy is used as the physical order of records in storage. Record access is done by navigating through the data structure using pointers combined with sequential accessing.

This model has been supported primarily by the IBM IMS DBMS, one of the earliest DBMSs. Various limitations of the model have been compensated at later IMS versions by additional logical hierarchies imposed on the base physical hierarchy.

Network model

In this model a hierarchical relationship between two record types (representing real-world entities) is established by the set construct. A set consists of circular linked lists where one record type, the set owner or parent, appears once in each circle, and a second record type, the subordinate or child, may appear multiple times in each circle. In this way a hierarchy may be established between any two record types, e.g., type A is the owner of B. At the same time another set may be defined where B is the owner of A. Thus all the sets comprise a general directed graph (ownership defines a direction), or network construct. Access to records is either sequential (usually in each record type) or by navigation in the circular linked lists. This model is more general and powerful than the hierarchical, and has been the most popular before being replaced by the Relational model. It has been standardized by CODASYL. Popular DBMS products that utilized it were Cincom Systems' Total and Cullinet's IDMS.