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MIS lecture 6


undefined, object
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smallest unit of data; binary digit (0,1)
group of bits that represent a single character, 8 bits = 1 byte
a group of words or a complete number
group of related fields
group of records of the same type
group of related files
person, place, thing, event about which information is maintained
description of a particlar entity
key field
indentifier field used to retrieve , update, sort a record
data hierarchy
bit, byte, field, record, file, database
problems with traditional file environment
- data redundancy
- data inconsistency
- program-data dependence
- lack of flexibility
- poor security
- lack of data sharing and availablity
data redundancy
the presence of duplicate data in multiple data files so that the same data are stored in more than one place or location
data inconsistency
the same attribute may have different values
program-data dependence
the coupling of data stored in files and the specific programs required to update and maintain those files such that changes in programs require changes to the data
lack of flexibility
a traditional file system can deliver routine scheduled reports after extensive programming efforts, but it cannot devliver ad-hoc reports or respond to unanticipated information requirements in a timely fashion
poor security
because there is little control or management of data, management will have no knowledge of who is accessing or even making changes to the organization's data
lack of data sharing and availablity
information cannot flow freely across different functional area of different parts of the organization. users find different values of teh same piece of information in two different systems, and hece, they may not use these systems because they cannot trust the accuracy of the data
Database Management System (DBMS)
- software for creating and maintaining databases
- permits firms to rationally manage data for the entire firm
- acts as interface between application programs and physical data files
- separates logical and design views of data
- solves many problems of the traditional data file approach
Data definition language (component of DBMS)
specifies content and structure of the database and defines each data element
data manipulation language
(component of DBMS)
used to process data in a database
data dictionary
(component of DBMS)
stores definitions of data elements and data characteristics
types of databases
- relational DBMS
- hierarchal and network DBMS
- orbject-oriented databases
Relational DBMS
- represents data as two-dimensional tables called relations
- relates data across tables based on common data element
Three basic operations in a relational database
- select
- join
- project
in a relational database, it creates subset of rows that meet specific criteria
in a relational database, combines relational tables to provide users with information
in a relational database,enables users to create new tables containing only relevent information
Hierarchical DBMS
- organizes data in tree-like structure
- supports one-to-many parent-child relationships
- prevalent in large legacy systems
Network DBMS
depicts data logically as many-to-many relationships
Disadvantages to Hierarchical and Network DBMS
- outdated
- less flexible compared to RDBMS
- lack support for ad-hoc and English language-like queries
Object-Oriented Databases
stores data and procedures as objects that can be retrieved and shared automatically
object-relational databases
provides capabilities of both object-oriented and relational DBMS
conceptual design (in designing databases)
abstract model of database from a business perspective
physical design (in designing databases)
detailed description of business information needs
entity-relationship diagram (in designing databases)
methodology for documenting databases illustrating relationships between database entities
process of creating small stable data structures from complex groups of data
centralized database
used by a single central processor or multiple processors in a client/server network

all corporate data is in one location

security is higher in central environments, risks lower

if data demands are highly decentralized, than a decentralized design is less costly and more flexible
distributed database
databases can be decentralized either by partitioning or by replicating
partitioned database
database is divided into segments or regions (i.e. eastern customers and western customers - two separate databases maintained in the two regions)
duplicated databses
database is completely duplicated at two or more locations - the separate databases are synchronized in off hours on a batch basis
online analytical processing (OLAP)
multidimensional data analysis

supports manipulation and analysis of large volumes of data from multiple dimensions/perspectives
database warehouse
supports reporting and query tools

stores current and historical data

consolidates data for management analysis and decision making
data mart
subset of data warehouse

contains summarized or highly focused portion of data for a specified function or group of users
data mining
tools for analyzing large pools of data

find hidden patterns and infer rules to predict trends
benefits of data warehouses
imporved and easy accessibility of information

ability to model and remodel the data
the web and hypermedia database
organizes data as a network of nodes

links nodes in pattern specified by user

supports text, graphic, sound, video, and executable programs
database server
computer in a client/server environment runs a DBMS to process SQL statements and perform database management tasks
application server
software handling all application operations

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