MANAGING DATA RESOURCES CHAPTER 8. MANAGING DATA RESOURCES

FILE ORGANIZATION BIT: Binary Digit (0,1;Y,N;On, Off) BYTE: Combination of BITS which represent a CHARACTER FIELD: Collection of BYTES which represent a Fact RECORD: Collection of FIELDS which reflect a TRANSACTION FILE: A Collection of Similar RECORDS

The layout of a personnel file in traditional file organization. Managing Digital Data The layout of a personnel file in traditional file organization.

FILE ORGANIZATION UPDATING SORTING DATABASE: An Organization’s Electronic Library of FILES Primary FIELD or Key: Field in Each Record Uniquely Identifies THIS Record For RETRIEVAL UPDATING SORTING

TRADITIONAL FILE ENVIRONMENT (FLAT FILE) DATA REDUNDANCY PROGRAM / DATA DEPENDENCY LACK OF FLEXIBILITY POOR SECURITY LACK OF DATA SHARING & AVAILABILITY Different information making up a student record retained in three different sites.

DATABASE MANAGEMENT SYSTEM (DBMS) SOFTWARE TO CREATE & MAINTAIN DATA *** ENABLES BUSINESS APPLICATIONS TO EXTRACT DATA *** INDEPENDENT OF SPECIFIC COMPUTER PROGRAMS DBMS

Managing Digital Data Traditional Files vs. Databases: Pros and Cons Traditional File Advantages Simplicity Efficiency Customization Database Advantages Reduced data redundancy Application/data independence Better control Flexibility

COMPONENTS OF DBMS: DBMS THE SCHEMA: describe the structure of the Database. DATA DEFINITION LANGUAGE: Defines Data Elements in Database and Used to construct the schema DATA MANIPULATION LANGUAGE: Manipulates Data for Applications DATA DICTIONARY: Maintains all information supplied by the developer when constructing the schema * DBMS

Data Definition Language (DDL) Data definition language to create a schema in NOMAD

Components of Database Management Systems Data Manipulation Language (DML) Used to query the database Figure 8.14 A Paradox query by example

DATA DICTIONARY A typical data dictionary for a staff file

ADVANTAGES OF DBMS: DBMS * REDUCES COMPLEXITY REDUCES DATA REDUNDANCY CENTRAL CONTROL OF DATA DEFINITIONS REDUCES PROGRAM / DATA DEPENDENCE REDUCES DEVELOPMENT / MAINTENANCE COSTS ENHANCES SYSTEM FLEXIBILITY INCREASES ACCESS / AVAILABILITY OF INFORMATION * DBMS

Database Models HIERARCHICAL DATA MODEL Records are related hierarchically – each category is a subcategory of the next level up 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 ROOT FIRST CHILD 2nd CHILD Ratings Salary Compensation Job Assignments Pension Insurance Health Benefits Employer

NETWORK DATA MODEL VARIATION OF HIERARCHICAL MODEL Allows a record to be linked to more than one parent USEFUL FOR MANY-TO-MANY RELATIONSHIPS NETWORK A B C 1 2

RELATIONAL DATA MODEL Consists of tables; links among entities are maintained with foreign keys DATA IN TABLE FORMAT RELATION: TABLE TUPLE: ROW (RECORD) IN TABLE FIELD: COLUMN (ATTRIBUTE) IN TABLE *

TYPES OR RELATIONS ONE-TO-ONE: STUDENT ID ONE-TO-MANY: CLASS STUDENT A B C MANY-TO-MANY: STUDENT A B C CLASS 1 2

Relational Operations Data Manipulation Select : is the selection of records that meets certain condition. Project: is the selection of certain columns from a table. Join : is the joining of data from multiple tables. Structured Query Language (SQL) International standard DDL and DML for relational DBMS. Advantages of using SQL Users do not need to learn different DDLs and DMLs. SQL can be embedded in widely used 3rd generation languages, increasing efficiency and effectiveness. Programmer not forced to rewrite statements since SQL statements are portable.

Advantages and disadvantages of database models

Database Architecture Shared Resource and Client/Server Systems Four basic client/server models 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

Database Architecture Distributed Databases Replication :Full copy of the entire database is stored at all sites A replicated database: each computer holds a copy of the entire database

Database Architecture Fragmentation: Parts of database are stored where they are most often accessed A fragmented database: each computer holds only the part of the database that is most frequently accessed by the local users

Web Databases Databases on the Web Catalogs Libraries Directories Client lists and profiles When linking a database to the Internet, consider Which application to use How to ensure Web surfers do not interfere with database updates How to maintain security

Data Warehousing Data warehouse Data Mining Collection of data that supports management decision making Phases in Building a Data Warehouse Extraction Phase Cleansing Phase Loading Phase Data Mining Selecting, exploring, and modeling data to discover unknown relationships

Data Warehousing

Data-Mining Potential applications of data-mining

DATABASE ADMINISTRATION DEFINES & ORGANIZES DATABASE STRUCTURE AND CONTENT DEVELOPS SECURITY PROCEDURES DEVELOPS DATABASE DOCUMENTATION MAINTAINS DBMS *

Ethical and Societal Issues A 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. Where is the Information Going? Many consumers provide information daily without being aware of where it is actually going. http://www.publicrecordfinder.com/ The Upside Database technology enables better and faster services.