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1. Wachemo University ( Durame Campus) Department of CS Fundamentals of database systems Chapter one Introduction Mr. Abraham Wolde (2023) 1

2. Outline Introduction to database system File based verses Database approach Characteristics of the Database Approach Users and actors of Database system 2

3. Introduction to database system A database is a collection of related data. we mean known facts that can be recorded and that have implicit meaning. For example, consider the names, tele -phone numbers, and addresses of the people you know. You may have recorded this data in an indexed address book or you may have stored it on a hard drive, using a personal computer and software such as Microsoft Access or Excel . This collection of related data with an implicit meaning is a database . 3

4. Cont’d… A database has the following implicit properties: A database represents some aspect of the real world, sometimes called the mini world or the universe of discourse ( UoD ). A database is a logically coherent collection of data with some inherent meaning. A random assortment of data cannot correctly be referred to as a database . A database i s designed, built , and populated with data for a specific purpose. It has an intended group of users and some preconceived applications in which these users are interested. 4

5. Cont’d… A database management system (DBMS) is a collection of programs that enables users to create and maintain a database. The DBMS is a general-purpose software sys-tem that facilitates the processes of defining, constructing, manipulating , and sharing databases among various users and applications . Defining a database involves specifying the data types, structures, and constraints of the data to be stored in the data-base. The database definition or descriptive information is also stored by the DBMS in the form of a database catalog or dictionary; it is called meta-data . Constructing the database is the process of storing the data on some storage medium that is con-trolled by the DBMS . 5

6. Cont’d … A typical large database may have a life cycle of many years, so the DBMS must be able to maintain the database system by allowing the system to evolve as requirements change over time. To complete our initial definitions, we will call the database and DBMS software together a database system. 6

7. File-Based Approach verses Database Approach File-based System File-based systems were an early attempt to computerize the manual filing system. File-based system is a collection of application programs that perform services for the end-users. Each program defines and manages its data. Each user defines and creates with a specific software the files he needs for a specific application e.g.. Spread sheet However, five types of problem are occurred in using the file-based approach : 7

8. Problems Of using file based approach Separation and isolation of data When data is isolated in separate files, it is more difficult for us to access data that should be available. Duplication of data i. Duplication is wasteful ii. Duplication can lead to loss of data integrity Data dependence The physical structure and storage of the data files and records are defined in the application program code. 8

9. Incompatible file formats The structures of the file are dependent on the application programming language. However file structure provided in one programming language such as direct file, indexed-sequential file which is available in COBOL programming, may be different from the structure generated by other programming language such as C. Fixed queries / proliferation of application programs   File-based systems are very dependent upon the application programmer. Any required queries or reports have to be written by the application programmer. 9

10. Database Approach: In order to overcome the limitations of the file-based approach, the concept of database and the Database Management System (DMS) was emerged in 60s.   A dvantages of data base approach 1. Control of data redundancy The database approach attempts to eliminate the redundancy by integrating the file. 2. Data consistency By eliminating or controlling redundancy, the database approach reduces the risk of inconsistencies occurring. 3.More information from the same amount of data With the integration of the operated data in the database approach, it may be possible to derive additional information for the same data. 10

11. 4. Sharing of data 5. Improved data integrity 6. Improved security 7. Enforcement of standards The integration of the database enforces the necessary standards including data formats, naming conventions, documentation standards, update procedures and access rules. 11

12. 8. Economy of scale 9. Balance of conflicting requirements 10. Improved data accessibility and responsiveness By having an integration in the database approach, data accessing can be crossed departmental boundaries. 11. Increased productivity 12. Improved maintenance Database approach provides a data independence . As a change of data structure in the database will be affect the application program, it simplifies database application maintenance. 13. Increased concurrency 14. Improved backing and recovery services 12

13. Disadvantage of database approach Complexity Size Cost of DBMS Cost of conversion Performance Higher impact of a failure 13

14. Characteristics of database approach The main characteristics of the database approach versus the file-processing approach are the following: 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 14

15. Self-Describing Nature of a Database System A fundamental characteristic of the database approach is that the database system contains not only the database itself but also a complete definition or description of the database structure and constraints . This definition is stored in the DBMS catalog , which contains information such as the structure of each file, the type and storage format of each data item, and various constraints on the data. The information stored in the catalog is called meta-data , and it describes the structure of the primary database. 15

16. Insulation between Programs and Data, and Data Abstraction In traditional file processing, the structure of data files is embedded in the application programs, so any changes to the structure of a file may require changing all pro-grams that access that file. By contrast, DBMS access programs do not require such changes in most cases . The structure of data files is stored in the DBMS catalog separately from the access programs. We call this property program-data independence. 16

17. Support of Multiple Views of the Data A database typically has many users, each of whom may require a different perspective or view of the database. A view may be a subset of the database or it may contain virtual data that is derived from the database files but is not explicitly stored. 17

18. Sharing of data and multiuser transaction processing A multiuser DBMS , as its name implies, must allow multiple users to access the data-base at the same time . This is essential if data for multiple applications is to be integrated and maintained in a single database . The concept of a transaction has become central to many database applications. A transaction is an executing program or process that includes one or more database accesses , such as reading or updating of database records. 18

19. Users and actors of Database system 1.Database administrator (DBA ) The DBA is responsible for authorizing access to the database, coordinating and monitoring its use, and acquiring software and hardware resources as needed. The DBA is accountable for problems such as security breaches and poor system response time. 2.Database designers are responsible for identifying the data to be stored in the data-base and for choosing appropriate structures to represent and store this data. It is the responsibility of database designers to communicate with all prospective database users in order to understand their requirements and to create a design that meets these requirements . 19

20. Cont’d... 3.End users are the people whose jobs require access to the database for querying, updating, and generating reports; the database primarily exists for their use. There are several categories of end users : Casual end users occasionally access the database, but they may need different information each time. Naive or parametric end users make up a sizable portion of database end users . Their main job function revolves around constantly querying and updating the database, using standard types of queries and updates. 20

21. Cont’d… C. Sophisticated end users include engineers, scientists, business analysts, and others who thoroughly familiarize themselves with the facilities of the DBMS in order to implement their own applications to meet their complex requirements. D. Standalone users maintain personal databases by using ready-made pro-gram packages that provide easy-to-use menu-based or graphics-based interfaces . 21

22. Cont’d… 4. System Analysts and Application Programmers ( Software Engineers) System analysts determine the requirements of end users, especially naive and parametric end users, and develop specifications for standard canned transactions that meet these requirements. Application programmers implement these specifications as programs; then they test, debug, document, and maintain these recorded transactions . 22

23. Question & Answer 23

24. Thank You !!! 24