Db lecture 2
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The document outlines the system development life cycle (SDLC) and database development process (DDP), detailing phases from initial study to maintenance. It also discusses the three-level ANSI-SPARC architecture, which establishes a framework for understanding database systems by separating user views from physical data storage. The key focus is on ensuring data independence at both logical and physical levels within database management.
Db lecture 2
- 1. Institute of SouthernPunjab, Multan Mr. Saif ur Rehman Khan BS (Computer Science) MS (Data Science, and Computer Science) Honors: Certified Android Developer, Research Assistant E-Mail: saifurrehman.khan@outlook.com
- 3. Lecture 02 - Objectives System Development Life Cycle (SDLC) Database Development Process (DDP) The Three-Level ANSI-SPARC Architecture 3
- 4. System Development Life Cycle (SDLC) 4
- 5. Information System Definition: Information systems are combinations of hardware, software, and telecommunications networks that people build and use to collect, create, and distribute useful data, typically in organizational settings. 5
- 6. System Development Life Cycle Definition: A traditional process for conducting an information systems development project is called System Development Life Cycle (SDLC). The SDLC is a complete set of steps that a team of information systems professionals, including database designers and programmers, follow in an organizations to specify, develop, maintain, and replace information system. Organization use many variations on the life cycle, and many identify anywhere from three to twenty different phases. This process is depicted in upcoming slides. Ref (Hoffer et al., 2005). 6
- 7. Continue… System Development Life Cycle (SDLC): The traditional methodology used to develop, maintain and replace information system. 7
- 8. Continue… 8
- 9. System Development Life Cycle 9
- 10. Database Development Process (DDP) 10
- 11. Database Development Process (DDP) Database Application development Process includes the Following steps: 1. Preliminary / initial Study 2. Requirement Analysis 3. Database Design 4. Physical Design 5. Implementation 6. Maintenance 11
- 12. Problems with Data Dependency If data is being changed then the program must be changed and vice versa For example if a library system has some attributes about book like. Book_id Book_name Book_title Book_author And after some time we add an other attribute like book_edition. So you need to change data but on other hand you have to change the program as well because program is dependent on data and vice versa It means that if you change the data in library system you will have to change Examination and Registration systems. 12
- 13. Preliminary Study 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. 13
- 14. Continue… 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. 14
- 15. Requirement Analysis 15 In second phase, The detailed functionality decisions made at this of the organization. study of the system and its stage decide the overall activity of an 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.
- 16. Example 16
- 17. Database Design 17 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.
- 18. Continue… 18 Cardinality (data modeling) In database design, the cardinality or fundamental principle of one data aspect with respect to another is a critical feature. The relationship of one to the other must be precise and exact between each other in order to explain how each aspect links together.
- 19. Physical Design 19 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.
- 20. Implementation 20 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. We can done coding with out implemented all previous phases correctly.
- 21. Maintenance 21 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.
- 22. The Three-Level ANSI-SPARC Architecture 22
- 23. 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 two-level approach with a system view called the schema and user views called subschemas. 23
- 24. Continue… 24 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.
- 25. Continue… 25 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.
- 26. Continue… 26 External Level: The user’s view of the database. This level describes that part of the database that is relevant to each user. Conceptual Level: The community view of the database. This level describes what data is stored in the database and the relationship among the data. Internal/ Physical Level: The physical representation of the database on the computer. This level describes how the data is stored in the database.
- 27. Example: 27
- 28. Continue… • 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. 28
- 29. Continue… 29
- 30. Continue… • 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:- • Each user should be able to access the same data, but have a different customized view of the data. • Users should not have to deal directly with physical database storage details. 30
- 31. Continue.. 31 • 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. • The Database Administrator (DBA) should be able to change the conceptual and database storage structures without affecting the users’ views.
- 32. Continue… 32 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
- 33. Continue… 33
- 34. Continue… 34 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.
- 35. Continue… 35 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.
- 36. Summary of Lecture System Development Life Cycle (SDLC) Database Development Process (DDP) The Three-Level ANSI-SPARC Architecture 36
- 37. END OF LECTURE 2 37
Editor's Notes
- #24: SPARC (Scalable Processor Architecture) is a 32- and 64-bit microprocessor architecture from Sun Microsystems that is based on reduced instruction set computing (RISC). SPARC has become a widely-used architecture for hardware used with UNIX-based operating systems, including Sun's own Solaris systems.