CS102B: Introduction to Information Systems. Minerva A. Lagarde

Transcription

1 CS102B: Introduction to Information Systems Minerva A. Lagarde

2 Module 1: Fundamental Database Concepts Introduction Objectives In this module, the student will learn: 1) Difference between data and information; 2) What a database is, what it does, and why database design is important; 3) How modern databases evolved from files and file systems 4) What a DBMS is, what it does, and how it fits into the database system 5) About types of database systems and database models.

3 Data vs. Information Data Raw facts No context Just text and numbers Information Data with context Processed data Value-added to data Summarized Organized Analyzed

4 Data vs. Information (con t.) For example: Data : 24 Information: 24 gold medals for the Philippines in the SEA Games (as of last night) 24 Hours in one (1) day 24, The title of a TV show starring Kieffer Sutherland.

5 Data vs. Information (con t.) Data constitute building blocks of information. Information is produced by processing data. Information reveals meaning of data. Accurate, timely, relevant information is key to decision making. Good decision making is key to organizational survival.

6 Database vs. DBMS Database is a collection of data, typically about one specific enterprise. Example: Employee records stored in a filing cabinet. Database management system (DBMS) a collection of interrelated data, plus the software and hardware required to access that data in a useful manner. Example: phone list stored in a personal computer, or a system run by a company that handles inventory, billing, ordering and payroll.

7 DBMS Continued Database management system is a collection of programs that enables users to create and maintain a database. - A general-purpose software system that facilitates the processes of defining, constructing, manipulating, and sharing databases among various users and applications.

8 Advantages of DBMS Improved data sharing end-users have better access to more and better-managed data. Improved data security - A DBMS provides a framework for better enforcement of data privacy and security policies. Minimized data inconsistency - The probability of data inconsistency is greatly reduced in a properly designed database. Improved data access query language allows quick answers to ad hoc (spur of the moment) queries. Improved decision making Increased end-user productivity

9 DBMS manages interaction Figure 1.1

10 Database system Database System = Database + DBMS software Users/Programmers Database system DBMS software Application Programs / Queries Software to Process Queries / Programs Software to Access Stored Data Stored database definition (meta-data) Stored database

11 Types of Databases Databases can be classified according to 1) the number of users, 2) the database location(s), and 3) the expected type and extent of use. Types of databases (according to number of users) a) single-user desktop database b) multi-user Workgroup database specific department within an organization. Enterprise database entire organization, supports many users.

12 Types of Databases (con t.) Types of databases (according to location) a) centralized database single site. b) distributed database several sites. Types of databases (according to expected type and extent of use) a) operational database designed primarily to support a company s day-to-day operations. (transactional or production database) b) data warehouse - focuses primarily on storing data used to generate information required to make tactical or strategic decisions.

13 Database design Database design activities that focus on the design of the database structure that will be used to store and manage end-user data. Importance of good design Poor design results in unwanted data redundancy. Poor design generates errors leading to bad decisions. Practical Approach Focus on principles and concepts of database design Importance of logical design

14 Evolution of File System Data Processing Manual File Systems paper-and-pencil type systems. First applications focused on clerical tasks Requests for information quickly followed Computerized File System file systems developed to address needs Data organized according to expected use Data Processing (DP) specialists computerized manual file systems

15 Figure 1.3: A Simple File System

16 Basic File Terminology Data Raw Facts Field Group of characters with specific meaning. Record Logically connected fields that describe a person, place, or thing. File Collection of related records

17 Table 1.1: Contents of the CUSTOMER file C_NAME = Customer name C_PHONE = Customer phone C_ADDRESS = Customer address C_ZIP = Customer zip code thousands of $ REN = Insurance renewal date A_NAME = Agent name A_PHONE = Agent phone TP = Insurance type AMT = Insurance policy amount, in

18 Recitation 1: A_NAME = Agent name A_PHONE = Agent phone A_ADDRESS = Agent address ZIP = Agent zip code HIRED = Agent date of hire YTD_PAY = Year-to-date pay YTD_FIT = Year-to-date federal income tax paid YTD_FICA = Year-to-date Social Security taxes paid YTD_SLS = Year-to-date sales DEP = Number of dependents 1) How many records do we have? 2) How many fields? 3) What is the file name?

19 File System Critique File System Data Management Requires extensive programming in thirdgeneration language (3GL) Time consuming Makes ad hoc queries impossible Leads to islands of information

20 File System Critique (Con t.) Data Dependence Change in file s data characteristics requires modification of data access programs Must tell program what to do and how Makes file systems cumbersome from programming and data management views Structural Dependence Change in file structure requires modification of related programs

21 File System Critique (Con t.) Data Redundancy Different and conflicting versions of same data Results of uncontrolled data redundancy Data anomalies Modification Insertion Deletion Data inconsistency Lack of data integrity

22 Data Integrity Data integrity defined as the condition in which all of the data in the database are consistent with the real-world events and conditions. In other words, data integrity means that: Data are accurate there are no data inconsistencies. Data are verifiable the data will always yield consistent results.

23 Database Systems Database consists of logically related data stored in a single repository Provides advantages over file system management approach Eliminates inconsistency, data anomalies, data dependency, and structural dependency problems Stores data structures, relationships, and access paths

24 Database vs. File Systems

25 Database System Environment

26 Database System - organization of components that define and regulate the collection, storage, management, and use of data within a database environment. From a general management point of view, the database system is composed of five major parts: hardware, software, people, procedures, and data.

27 Hardware refers to all of the system s physical devices; for example: computers (PCs, workstations, servers, and supercomputers), storage devices, printers, network devices (hubs, switches, routers, fiber optics).

28 Software Although the most readily identified software is the DBMS itself, to make the database system function fully, three types of software are needed: 1) operating system software, 2) DBMS software, and 3) Application programs and utilities.

29 Operating System - manages all hardware components and makes it possible for all other software to run on the computers. Examples of operating system software include Microsoft Windows, Linux, Mac OS, UNIX, and MVS.

30 DBMS Software - manages the database within the database system. Some examples of DBMS software: Microsoft s SQL Server, Oracle Corporation s Oracle, Sun s MySQL, and IBM s DB2.

31 Application programs and utility software - used to access and manipulate data in the DBMS and to manage the computer environment in which data access and manipulation take place. Application programs commonly used to access data found within the database to generate reports, tabulations, and other information to facilitate decision making. Utilities tools used to help manage the database system s computer components. For example, graphical user interfaces (GUIs) to help create database structures, control database access, and monitor database operations.

32 People - This component includes all users of the database system. On the basis of primary job functions, five types of users can be identified in a database system: 1) system administrators 2) database administrators 3) Database designers 4) system analysts and programmers, and 5) end users.

33 People System administrators oversee the database system s general operations. Database administrators (DBAs) manage the DBMS and ensure that the database is functioning properly. Database designers design the database structure. Architect of the database. * If the database design is poor, even the best application programmers and the most dedicated DBAs cannot produce a useful database environment.

34 System analysts and programmers design and implement the application programs. They design and create the data entry screens, reports, and procedures through which end users access and manipulate the database s data. End users people who use the application programs to run the organization s daily operations. For example, salesclerks, supervisors, managers, and directors are all classified as end users.

35 Procedures - instructions and rules that govern the design and use of the database system. - enforce the standards by which business is conducted within the organization and with customers. - ensure that there is an organized way to monitor and audit both the data that enter the database and the information that is generated through the use of those data.

36 Data - the collection of facts stored in the database. - Raw material from which information is generated * The determination of what data are to be entered into the database and how those data are to be organized is a vital part of the database designer s job.

37 DBMS Functions 1. Data dictionary management - The DBMS stores definitions of the data elements and their relationships (metadata) in a data dictionary. In turn, all programs that access the data in the database work through the DBMS. 2. Data storage management - The DBMS creates and manages the complex structures required for data storage, thus relieving you from the difficult task of defining and programming the physical data characteristics. Data storage management is also important for database performance tuning. Performance tuning relates to the activities that make the database perform more efficiently in terms of storage and access speed.

38 Fig Illustrating data storage management in Oracle

39 More on data storage management Although the user sees the database as a single data storage unit, the DBMS actually stores the database in multiple physical data files. (See Figure 1.6.) Such data files may even be stored on different storage media. Therefore, the DBMS doesn t have to wait for one disk request to finish before the next one starts. In other words, the DBMS can fulfill database requests concurrently.

40 3. Data transformation and presentation The DBMS transforms entered data to conform to required data structures. For example, imagine an enterprise database used by a multinational company. An end user in England would expect to enter data such as July 11, 2010, as 11/07/2010. In contrast, the same date would be entered in the United States as 07/11/2010. Regardless of the data presentation format, the DBMS must manage the date in the proper format for each country.

41 4. Security Management - The DBMS creates a security system that enforces user security and data privacy. Security rules determine which users can access the database, which data items each user can access, and which data operations (read, add, delete, or modify) the user can perform. 5. Multiuser access control - To provide data integrity and data consistency, the DBMS uses sophisticated algorithms to ensure that multiple users can access the database concurrently without compromising the integrity of the database.

42 6. Backup and recovery management - The DBMS provides backup and data recovery to ensure data safety and integrity. Current DBMS systems provide special utilities that allow the DBA to perform routine and special backup and restore procedures. Recovery management deals with the recovery of the database after a failure, such as a bad sector in the disk or a power failure. Such capability is critical to preserving the database s integrity.

43 7. Data integrity management - The DBMS promotes and enforces integrity rules, thus minimizing data redundancy and maximizing data consistency. The data relationships stored in the data dictionary are used to enforce data integrity. Ensuring data integrity is especially important in transaction-oriented database systems.

44 8. Database access languages and application programming interfaces - The DBMS provides data access through a query language. A query language is a nonprocedural language one that lets the user specify what must be done without having to specify how it is to be done. Structured Query Language (SQL) is the de facto query language and data access standard supported by the majority of DBMS vendors.

45 9. Database communication interfaces Currentgeneration DBMSs accept end-user requests via multiple, different network environments. For example, the DBMS might provide access to the database via the Internet through the use of Web browsers such as Mozilla Firefox or Microsoft Internet Explorer. In this environment, communications can be accomplished in several ways: - End users can generate answers to queries by filling in screen forms through their preferred Web browser. - The DBMS can automatically publish predefined reports on a Website. - The DBMS can connect to third-party systems to distribute information via or other productivity applications.

46 Quiz 1: 1) Difference between data and information (2 points) 2) Types of database according to number of users (2 points) 3) Advantage of database system (1 point)