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Introduction to Database Processing

Introduction to Database Processing. IS 240 – Database Management Lecture #1 – 2004-01-15 Prof. M. E. Kabay, PhD, CISSP Norwich University mkabay@norwich.edu http://www2.norwich.edu/mkabay. Topics. Why study DBMS? DBMS Applications Historical Overview Defining “Database”

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Introduction to Database Processing

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  1. Introduction to Database Processing IS 240 – Database Management Lecture #1 – 2004-01-15Prof. M. E. Kabay, PhD, CISSP Norwich University mkabay@norwich.edu http://www2.norwich.edu/mkabay

  2. Topics • Why study DBMS? • DBMS Applications • Historical Overview • Defining “Database” • How a DBMS Is Used • Historical Development of DBMS • Some Fundamental Issues in DB Applications • HOMEWORK

  3. Why study DBMS? • Central technology of today’s information technology (IT) • Teaches orderly analysis of data requirements and relationships • Opportunity to understand internals underlying externals of applications • Provides basis for rapid assimilation and application of wide range of specific DBMS tools • Structured Query Language (SQL) almost universally used in industry • Increases likelihood of good jobs

  4. DBMS Applications • DBMS = database management system • Database contains one or more tables (files, datasets) • columns = fields • rows = records • Relations among tables help navigate DB • DB Application allows access to database • usable formats • data entry • reports

  5. Concurrency • Single-user database allows only one user at a time • aka exclusive access • Types of access permissions • READ • WRITE • APPEND • LOCK • Multi-user databases need to protect against damage to records

  6. Concurrency (cont’d) TIME • Joe accesses Widget record • Shakheena accesses Widget record • Inventory shows 25 to both • Joe takes out 10 • Application writes out record to DB • Inventory now shows 15 • Shakheena takes out 5 from her copy of data (25) • Inventory now shows 20

  7. Historical Overview • How did people handle masses of data? • Manual systems • Clay tablets • Parchment • Paper • Abacus • Punch cards (1890-1960) • File systems (1950-present) • DBMS (1970-present)

  8. Problems with File Systems • Separated, isolated data • Duplication of data • File-format dependency • File incompatibilities • Hard to show useful views of data

  9. Problems: Separated, Isolated Data • Multiple files for different aspects of system • Linkages handled entirely by application programming • Coordinate access to multiple files for different functions • Some databases have hundreds of files

  10. Problems: Duplication Of Data • Early collections of files duplicated data • e.g., identifiers (name, address. . . .) • Easy to generate discrepancies • copies of data in different records and different files could diverge from each other • Frustrating for users and clients • enter same information over and over • Results inconsistent, contradictory • send invoice to old address in one program, new address in other program

  11. Problems: File-format Dependency • Structure of data files hard-coded in application program • All changes to data files requires modification of programs • rewrite data description • rewrite special code for linking or searching • recompile source code to generate object • update documentation

  12. Problems: File Incompatibilities • Different analysts and programmers used different data definitions • NAME has 20 chars • NAME has 40 chars • Different names for fields • SSN vs SS# • LAST_NAME vs L_NAME • Different record structures • LAST | FIRST | STREET1 | STREET 2 | CITY • NAME | ADDRESS | CITY_&_STATE

  13. Problems: Hard To Show Useful Views Of Data • Combining fields from different records in different files necessary for most users • reports • on-screen visualization • Every report / screen requires special programming • find data (often by serial search) • place in output in specific positions • all require a great deal of programming

  14. Defining “Database” • “A database is a self-describing collection of integrated records.” • Self-describing • Integrated • Model of a model

  15. DATA How a DBMS Is Used APPLICATION PROGRAMS TOOLS API QUERY INTERNALS DATA DICTIONARY

  16. Self-describing • Databases have data dictionaries • aka data directory or metadata • Data dictionary supports independence between programs and database • Change in data dictionary does NOT usually require change in program • Enormous reduction in programming complexity and maintenance of programs • Data dictionary supports independence between database and documentation • Constant problem: bad documentation • DBMS helps reduce dependence on manual documents

  17. Integrated • Files are accessed in systematic way • Special files maintain indexes that help speed access • “Find all records where name begins with S” • Find records where city_population > 750,000 and household_median_income > $50,000 • Application metadata can include report structures • “Print the invoice for Mrs Smith’s fuel oil deliveries this month”

  18. Model of a model • Databases are designed by people • DB does not directly reflect “reality” • DB reflects designer’s decisions about how to represent user’s perceptions of what matters • “The availability of a tool determines perceptions of what’s a reasonable request.” • As users learn to use their DB, they begin to think in new ways • Recognize new possibilities, need new functions • Databases evolve as they are used

  19. Historical Development of DBMS • 1970s: E. F. Codd – relational DB model • normalization of data • reduce repetition • 1980s: Microcomputers: dBase II • not DBMS • not relational • but interfaces improved • mainframe products ported to PCs

  20. Historical Development of DBMS (cont’d) • Mid-1980s: client-server architecture • Link inexpensive computers in networks (LANs) • Store data on servers • Run client programs on workstationsfor user interface, some computations, reports • 1990s: Web-based systems • Web exploded into use ~1993 • Common interface: browser • client software reading standard formatting codes – HTML, XML, JAVA

  21. Some Fundamental Issues in DB Applications • Ethical constraints on data gathering and usage (details later in course) • How do we protect data subjects against abuse? • Security (details later) • confidentiality • control • integrity • authenticity • availability • utility

  22. Homework • Study Kroenke Chapter 1 using SQ3R • By next Thu, 23 Jan 2003: required • Write out answers to each of the Group 1; print your responses and bring them to class • Questions 1.1 through 1.23 using a computer (23 points) • Short (½ to 1 page) response to Project A on page 23 (2 points) • Short response to Project B (2 points)

  23. For Extra Credit 1 point each: optional • Write out & print answers by Thu 30 Jan 2003 • FiredUp Project Question A • FiredUp Project Question B (only if A done)

  24. Preparation for Next Class • Review Kroenke Chapter 1 • Scan Kroenke Chapter 2 • Apply SQ3R global scan to Ferrett et al • Study Ferrett et al Projects 1 & 2 • Load files from Ferrett CD-ROM onto your own computer if you have one • Amazon has the 1st chapter of Kroenke; search on Kroenke and look for the 8th edition. • Also see the Kroenke Web site at http://www.prenhall.com/kroenke

  25. DISCUSSION

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