chapter 1-Introduction Fundamentals of database system.pdf

Fundamentals of Database system Chapter one: Introduction to database system Prepared by: Misganaw Abeje University of Gondar College Of Informatics Department of computer science Misganaw.Abeje13@gmail.com

Outline  What is data  What is database and DBMS  Characteristics of database  Data base system and file system  Advantages of DB approach and its characteristics  Actors on Scene  Database Terminology BY: MA

Data  Data are the raw (unorganized) facts about things like people, places, events or concept that have inherent meaning, which is useless By themselves ).  The decision maker really needs is information,  Databases and database technology are having a major impact on the growing use of computers.  Databases play a critical role in almost all areas where computers are used, including business, engineering, medicine, law, education, and library BY: MA

What is database?  database is a collection of related data. E.g. Address book .An address book mainly contains the name, telephone number and address.  A database is a well organized, logically related and shared collection of data that is designed to meet the information needs of various users in an organization.  The database is an integrated collection of facts about an organization. – Organization can be a University, Insurance companies, Banks, Airlines, Governmental and Non-governmental Organizations etc.  The database is used as a central data source for other applications BY: MA

Implicit properties of database:  A database represents some aspect of the real world  Database is a logically coherent collection of data with some inherent meaning  A database is designed, built, and populated with data for a specific purpose.  In other words, the interaction with events in the real world. BY: MA

What is database management system (DBMS)  It is a collection of programs that enables users to create and maintain a database.  The DBMS is hence a general-purpose software system that facilitates the processes: – Defining a database: involves specifying the data types, structures, and constraints for the data to be stored in the database. – Constructing the database: is the process of storing the data itself on some storage medium that is controlled by the DBMS. – Manipulating a database includes such functions as querying the database to retrieve specific data, updating the database to reflect the mini-world, and generating reports from the data. BY: MA

Data base system and file system  Data management passes through the different levels of development.  These levels could best be described by categorizing the levels into three levels of development. Even though there is an advantage and a problem overcome at each new level.  The major three levels are; 1. Manual Approach 2. Traditional File Based Approach 3. Database Approach BY: MA

Manual File Handling Systems  In this approach, data storage and retrieval follows the primitive and traditional way of information handling where cards and paper are used for the purpose performed using human labor.  Each of the files containing various kinds of information is labeled and stored in one or more cabinets.  The cabinets could be kept in safe places for security purpose based on the sensitivity of the information contained in it.  Insertion and retrieval is done by searching first for the right cabinet then for the right file then the information.  Some Examples Personal Calendar, personal profile BY: MA

Limitations of the Manual approach – Prone to error – Difficult to update, retrieve, integrate – You have the data but it is difficult to compile the information – Limited to small size information – Cross referencing is difficult  An alternative approach of data handling is a computerized way of dealing with the information.  Two computerized approaches evolved: – – File based approach → decentralized – – Database approach→ centralized BY: MA

File-Based Approach  File based systems were an early attempt to computerize the manual filing system by use of computer system.  This approach is the decentralized computerized data handling method.  A collection of application programs perform services for the end-users. In such systems, every application program that provides service to end users define and manage its own data BY: MA

 Such systems have number of programs for each of the different applications in the organization.  Since every application defines and manages its own data, the system is subjected to serious data duplication.  File, in traditional file based approach, is a collection of records which contains logically related data.  This approach is to develop a number of programs for each different application BY: MA

Limitations of the Traditional File Based approach  Data Redundancy (Duplication of data) – Same data is held by different programs and Wasted space  Separation or Isolation of Data: Available information in one application may not be known.  Limited data sharing  Lengthy development and maintenance time  Data dependency on the application – Each application program must have its own processing routines  Incompatible file formats (Lack of Data Sharing and Availability) BY: MA

Cont…  Data Inconsistency and confusion  Poor Security and administration  The limitations for the traditional file based data handling approach arise from two basic reasons. 1. Definition of the data is embedded in the application program which makes it difficult to modify the database definition easily. 2. No control over the access and manipulation of the data beyond that imposed by the application programs. The most significant problem experienced by the traditional file based approach of data handling is the “update anomalies” BY: MA

Cont… We have three types of update anomalies; 1. Modification Anomalies: a problem experienced when one or more data value is modified on one application program but not on others containing the same data set. 2. Deletion Anomalies: a problem encountered where one record set is deleted from one application but remain untouched in other application programs. 3. Insertion Anomalies: a problem experienced whenever there is new data item to be recorded, and the recording is not made in all the applications. And when same data item is inserted at different applications, there could be errors in encoding which makes the new data item to be considered as a totally different object. BY: MA

Database Approach  To become more effective, database approach is required.  A Database Approach is shared collection of logically related data, designed to meet the information needs of an organization. (Centralized System). – Shared collection – can be used simultaneously by many departments and users. – Logically related - comprises the important objects and the relationships between these objects. – Description of the data – the system catalog (data dictionary or meta-data) provides description of data to enable data independence (program–data independence). BY: MA

Cont..  Database is a collection of logically related data where these logically related data comprises entities, attributes, relationships, and business rules of an organization's info.  Database is just a computerized record keeping system  In addition to containing data required by an organization, database also contains a description of the data which called as “Metadata” or “Data Dictionary” or “Data about Data”. Since it is called a self descriptive collection on integrated records.  The purpose of a database is to store information and to allow users to retrieve and update that information on demand.  Database is designed once and used simultaneously by many users. BY: MA

Characteristics of database approach  A number of characteristics distinguish the database approach from the traditional approach of programming with files.  Self-Describing Nature of a Database System  Insulation between Programs and Data, and Data Abstraction  Support of Multiple Views of the Data  Sharing of Data and Multiuser Transaction Processing BY: MA

Advantages of Using the DBMS Approach  Controlling Redundancy  Restricting Unauthorized Access  Providing Backup and Recovery  Data Abstraction  Data Independence  Support Multiple view for different Users BY: MA

Actors on the Scene  Database Administrators: – The DBA is responsible for authorizing access to the database, for coordinating and monitoring its use, and for acquiring software and hardware resources as needed. – The DBA is accountable for problems such as breach of security or poor system response time. BY: MA

 Database Designers: – Database designers are responsible for identifying the data to be stored in the database and for choosing appropriate structures to represent and store this data. – These tasks are mostly undertaken before the database is actually implemented and populated with data. – It is the responsibility of database designers to communicate with all prospective database users, in order to understand their requirements. BY: MA

 End Users: – End users are the people whose jobs require access to the database for querying, updating, and generating reports. BY: MA

 System Analysts and Application Programmers (Software Engineers) – determine the requirements of end users, especially naive and parametric end users, and develop specifications for canned transactions that meet these requirements. – Application programmers implement these specifications as programs; then they test, debug, document, and maintain these canned transactions. – Such analysts and programmers (nowadays called software engineers) . BY: MA

Basic Database Terminologies  Enterprise – an organization : A library, a bank, a university, etc.  Entity – Person, place, thing, or event (property of an entity) – An "object" in the real world that we are interested in: – The object student is an entity  Attribute (Field) – A character or group of characters (alphabetic or numeric), that has a specific meaning. Eg. Name, age, telephone, grade, sex, etc. BY: MA

 Record – A logically connected set of one or more Attributes that describe a person, place or thing. (Logically related data)  File – A collection of related records. For example, a file might contain data about customers; or students of a certain department in a university.  Database – Collection of Files BY: MA

Different database models  Hierarchical data model – Organize data in a tree structure – There is a hierarchy of parent and child – Data modeling to be one-to-many  Network data model – The same as hierarchical, but network model permits the modeling of many-to-many relationship – A child can have more than one parent BY: MA

 Relational data model – Stores data in the form of tables – A table is a collection of records – Each table corresponds to an entity – Allows the definition of data and integrity constraints  Object-oriented data model – Faster than relational database model – Applications require less code – Add database functionality to object programming language BY: MA

chapter 1-Introduction Fundamentals of database system.pdf

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chapter 1-Introduction Fundamentals of database system.pdf