Chapter 8

1. Chapter 8 Data and Knowledge Management

2. Learning Objectives • When you finish this chapter, you will • Know the difference between traditional file organization methods and the database approach. • Know how database management systems are used to construct databases, populate them with data, and manipulate the data to produce information. • Be familiar with the different database models and the advantages and disadvantages of each model.

3. Learning Objectives • Know the most important features and operations of a relational database. • Understand how databases are changing business operations across industries and what impact they might have on our personal lives. • Understand the concepts of data warehousing and data-mining and their use in business. • Recognize the need for knowledge storage and management and be able to give examples of the ways knowledge is managed in organizations.

4. Managing Digital Data • The Traditional File Approach • Different pieces of information are stored as a string of bytes – there are no labels or categorizations • i.e.: Flat File • Advantages • Efficient use of space • Disadvantages • Program/Data Dependency • High Data Redundancy • Low Data Integrity

5. Figure 8.1 The layout of a personnel file in traditional file organization. Flat File Layouts

6. Figure 8.2 Different information making up a student record retained in three different sites. Data Redundancy

7. Moving to Databases • Maintain and manipulate data about entities • Entity: any object chosen to collect data about • Field: one piece of information about entity • Fields can hold text, numbers, pictures, sounds and video clips • Record: several fields related to same entity • File: collection of related records

8. Figure 8.3 Data hierarchy Managing Digital Data

9. Database Management System (DBMS) • The program used to build databases, populate them with data, and manipulate the data • Queries: Request data from specified fields • Security: Giving users different views addresses security issue

10. Figure 8.4 Different database views reveal different combinations of data Securing Different Data Views

11. Figure 8.5 Different views of one employee database Managing Digital Data

12. Database Advantages Reduced data redundancy Application/data independence Better control Greater flexibility Traditional File Advantages Simplicity Efficiency Customization Traditional File Disadvantage Creates data redundancy and application-data dependence Does not support as tight control over data currency, accuracy, and integrity as database approach Provides less flexibility in data maintenance Traditional Files vs. Databases: Pros and Cons

13. Figure 8.6 Advantages and disadvantages of database models Database Models Database model: general logical structure which stores records within a database.

14. Database Models • The Hierarchical Model • Records are related hierarchically -- each category is a subcategory of the next level up • One:Many relationships (Parent:Child) • Disadvantages of hierarchical databases • To retrieve a record, a user must start at the root and navigate the hierarchy. • If a link is broken, the entire branch is lost. • Requires considerable data redundancy.

15. Database Models • The Network Model • Allows a record to be linked to more than one parent • Supports many-to-many (M:M) relationships • Advantage of the network model • Reduced data redundancy • Disadvantages of the network model • Complicated to build and difficult to maintain • Difficult to navigate • Relationship Spaghetti

16. Database Models • The Relational Model • Consists of tables; links among entities are maintained with foreign keys • Advantages of relational databases • Same advantages of a network database without the complications • Easier to conceptualize and maintain • Virtually all DBMSs offered for microcomputers accommodate the relational model

17. Database Models • Keys in a Relational Database • A field whose values identify records • Either for display or for processing • Primary Key • Unique key • Linking • To link records from one table with records of another table, the table must have one field in common • Repeated field; a primary key in one table and a foreign key field in another table

18. Other Database Models • The Object-Oriented Structure • An object consists of both data and the procedures necessary to manipulate the data (Encapsulation) • Affords maintenance of data along with the applications that process them • Entity-Relationship Diagrams • Conceptual (logical) blueprint of a database • Graphical representation of all entity relationships

19. Figure 8.10 An entity-relationship diagram An Entity-Relationship Diagram

20. Components of Database Management Systems • The Schema • Describes the structure of the database • Types of Data fields can hold (alphanumeric, numeric, date…) • Building a Database happens after the schema is defined • The Data Dictionary (Metadata – aka Data about the Data) • Maintains all information supplied by the developer when constructing the schema • Record names and types, file names, field names and types, relationships, roles and responsibilities

21. Figure 8.13 A typical data dictionary for a staff file Components of Database Management Systems

22. Components of Database Management Systems • Data Definition Language (DDL) • Subprogram used to construct the schema • Commands and protocols • Can be presented in a series of interactive forms for the designer to complete • Something most of us will never directly encounter

23. Components of Database Management Systems • Data Manipulation Language (DML) • Software used to query the database • Some require sophisticated commands: • FROM EMPLOYEE LIST LAST_NAME DEPARTNMENT SALARY WHERE DEPARTMENT =‘4530’ AND SALARY <25000 • Sometimes this is hidden from the user – Query by Example is used instead • This is the most common interface we will encounter

24. Relational Operations • A relational operation creates a temporary table used to manipulate data • Select: Select records that meet a certain criteria • Project: Select columns from a particular table • Join: Combination of data from multiple tables to form a new table

25. Figure 8.16 A join table of professors and their students A Join Table

26. Relational Operations • Structured Query Language (SQL) [pr: See-kwul] • International standard DDL and DML for relational DBMS • Advantages of using SQL • Users do not need to learn different DDLs and DMLs • Easy to remember / intuitive commands • SQL can be embedded in widely used 3rd generation languages (such as COBOL), increasing efficiency and effectiveness • Programmer not forced to rewrite statements since SQL statements are portable between operating systems

27. Figure 8.17 Popular DBMSs Popular DBMS’s

28. Database Architecture • Database Architecture refers to both the physical and logical layouts • Distributed Databases (geographically remote sites) • Replication • Full copy of the entire database is stored at all sites

29. Figure 8.18 A replicated database: each computer holds a copy of the entire database Replicated Database

30. Database Architecture • Database Architecture refers to both the physical and logical layouts • Distributed Databases (geographically remote sites) • Replication • Full copy of the entire database is stored at all sites • Fragmentation • Parts of database are stored where they are most often accessed

31. Figure 8.19 A fragmented database: each computer holds only the part of the database that is most frequently accessed by the local users Fragmented Database

32. Database Architecture • Shared Resource and Client/Server Systems • Four basic client/server models (Access remotely / process locally) • Applications run at a server • Applications run on local PCs • Applications run on both the local PCs and the server • Applications and key elements of the database are split between the PCs and the server

33. Figure 8.20 Shared resource and client/server architectures Database Architecture

34. Web Databases • Databases on the Web • Catalogs • Libraries • Directories • Client lists and profiles • Points to consider (when linking a database to the Internet) • Which application to use • How to ensure Web surfers do not interfere with database updates • How to maintain security

35. Data Warehousing • Data warehouse • Collection of data that supports management decision making • From Database to Data Warehouse • Hardware • Data and Software • Phases in Building a Data Warehouse • Extraction Phase • Cleansing Phase • Loading Phase

36. Figure 8.21 Data are warehoused for analysis and reporting Data Warehousing

37. Data Mining • Selecting, exploring, and modeling data to discover unknown relationships

38. Figure 8.22 Potential applications of data-mining Data Mining

39. Knowledge Management • Where to find information • Gathering, organizing, sharing, analyzing and disseminating knowledge to improve an organization’s performance • Transfer knowledge into databases • Filter and separate the most relevant knowledge • Organize knowledge in databases that either • Allow other employees to easily access the knowledge • “Push” specific knowledge to employees based on their prespecified needs

40. Ethical and Societal IssuesA Too-Risky Info Highway • Out of Hand -- Out of Control • DBMSs allow organizations to collect, maintain, and sell vast amounts of private personal data easily. • The Web: A Source of Data Collection • Many consumers provide information daily without being aware of it.

41. Ethical and Societal IssuesA Too-Risky Info Highway • Our Finances Exposed • Companies sharing private financial information with other organizations. • The Upside • Database technology enables better and faster services. • Makes markets more competitive.