Institute of Southern Punjab, Multan

Transcription

1 Institute of Southern Punjab, Multan Mr. Muhammad Nouman Farooq BSC-H (Computer Science) MS (Telecomm. & Networks) Honors: Magna Cumm Laude Honors Degree Gold Medalist! Blog Url: noumanfarooqatisp.wordpress.com 1

2 Database Systems Database Environment Lecture# 2 2

3 Lecture 2: Database Environment System Development Life Cycle (SDLC) Database Development Process (DDP) The Three-Level ANSI-SPARC Architecture 3

4 System Development Life Cycle (SDLC) 4

5 5

6 6

7 Database Development Process (DDP) 7

8 Database Development Process (DDP) Database Application development Process includes the Following Stages or steps: 1. Preliminary Study 2. Requirement Analysis 3. Database Design 4. Physical Design 5. Implementation 6. Maintenance 8

9 Continued 9

10 Preliminary Study Design of database is carried out in a number of steps; these steps play important role in the design process and need to be given proper attention. First Phase of the database development process is the Preliminary Study, which is based on the proper study of the system. It means that all the parts of the systems, or the section of the subject organization for which we intend to develop the system must be studied. 10

11 Continued We should find the relation or interaction of different section of the organization with each other and should understand the way information flows between different sections of the organization. Moreover it should also be made clear that what processing is performed at each stage of the system. 11

12 Requirement Analysis Once we have investigated the organization for its different sections and the way data flows between those sections; Detailed study of the system is started to find out the requirements of each section. In second phase, The detailed study of the system and its functionality decisions made at this stage decide the overall activity of the organization. Requirements of one section of the organization are fulfilled in such a way that all the sections in the organization are supporting each other. 12

13 Continued For example we can say that the results produced by the processing taking place at one section are used as input for another section. 13

14 Database Design Third phase in the database development process is the database design. This is a technical phase of the process and need handsome skill as a Database Administrator. This is the phase where the conceptual design of the database is created. It also known as Conceptual Data Modeling. Entities are identified and given attributes, relationships are built and different types of relationship are performed by assigning cardinalities. 14

15 Physical Design In fourth phase, The choice of the DBMS is made on the basis of requirements and the environment in which the system will operate. Implementing a database on a specific DBMS is very important because it involves the major financial investment of the organization, and can not be reverted in case a selected DBMS in not capable of providing the desired efficiency. Also, Assigning meaningful Data Types, Constraints/Limitations and De-Normalization of Data where required by the real time scenario/system are to be finalized and processed in this phase. 15

16 Implementation This phase is specific to writing the application programs needed to carry out different activities according to user requirements. We must write application programs in this phase by using MySQL (mai-structured query language) by using DBMS engine known as XAMPP (Cross platform apache MySequel PHP Perl). We can done coding with out any logical error; If we have implemented all previous phases of database development process correctly. 16

17 Maintenance Maintenance means to fine tune the system and check that the designed applications systems are fulfilling the purpose for which they are meant. Also, this phase may involve designing any new application for the enhancement of the system. Or an already working application may need to be updated or modified to remove any errors or to add some functionality in the system. 17

18 Continued All these stages are necessary and must be given the necessary attention at each level to get properly working and good system design and a better working environment. 18

19 The Three-Level ANSI-SPARC Architecture 19

20 The Three-Level ANSI-SPARC Architecture An early proposal for a standard terminology and general architecture for database systems was produced in 1971 by the Data Base Task Group (DBTG) appointed by the Conference on Data Systems and Languages (CODASYL, 1971). The Data Base Task Group (DBTG) recognized the need for a twolevel approach with a system view called the schema and user views called subschemas. 20

21 Continued The American National Standards Institute (ANSI) Standards Planning and Requirements Committee (SPARC), ANSI/X3/SPARC, produced a similar terminology and architecture in 1975 (ANSI, 1975). ANSI-SPARC recognized the need for a three-level approach. Although, The ANSI-SPARC model did not become a standard, It still provides a basis for understanding some of the functionality of a DBMS. 21

22 Continued The levels form a three-level architecture comprising an External, Conceptual, and an Internal level. The way users observe the data is called the External Level (Front End). The way the DBMS and the Operating System perceive/stores the data (Back End) is the Internal Level. The Conceptual Level provides both the mapping and the desired independence between the external and internal levels. 22

23 Continued 23

24 Continued 24

25 Continued The overall Description/Skeleton structure of the database is called the database schema. At the highest level, we have multiple external schemas (also called subschemas) that correspond to different views of the data. At the conceptual level, we have the conceptual schema, which describes all the entities, attributes, and relationships together with integrity constraints. At the lowest level, we have the internal schema, which is a complete description of the internal model, containing the definitions of stored records, the methods of representation, the data fields, and the indexes and storage structures used. There is only one conceptual schema and one internal schema per database. 25

26 Continued 26

27 Continued The objective of the three-level architecture is to separate each user s view of the database from the way the database is physically represented. There are several reasons why this separation is desirable:- 1. Each user should be able to access the same data, but have a different customized view of the data. 2. Users should not have to deal directly with physical database storage details. 27

28 Continued 4. The internal structure of the database should be unaffected by changes to the physical aspects of storage, such as the changeover to a new storage device. 5. The Database Administrator (DBA) should be able to change the conceptual and database storage structures without affecting the users views. 28

29 Continued A major objective for the three-level architecture is to provide data independence, which means that upper levels are unaffected by changes to lower levels. There are two kinds of data independence: - 1. Logical Data Independence. 2. Physical Data Independence. 29

30 Continued 30

31 Continued 1. Logical Data Independence: - Changes to the conceptual schema, such as the addition or removal of new entities, attributes, or relationships, should be possible without having to change existing external schemas or having to rewrite application programs. Clearly, the users for whom the changes have been made need to be aware of them, but what is important is that other users should not be. 31

32 Continued 2. Physical Data Independence: - Changes to the internal schema, such as using different file storage structures, using different storage devices should be possible without having to change the conceptual or external schemas. 32

33 Chapter 2 from: - Recommended Readings Modern Database Management 8 th Edition by Jeffery A. Hoffer, Prescott and McFadden (Page No ) Database Systems-A Practical Approach to Design, Implementation and Management by Thomas Connolly and Carolyn BEGG, 4 th Edition (Page No ) Fundamentals of Database Systems 6 th Navathe (Page No ) Edition by Elmasri and 33

34 Summary of Lecture Lecture 2 System Development Life Cycle (SDLC) Database Development Process (DDP) The Three-Level ANSI-SPARC Architecture 34

35 END OF LECTURE 2 35