 |  Using Information Technology: A Practical Introduction to Computers and Communications, 5/e Brian K. Williams
Stacey Sawyer
FILES, DATABASES, & E-COMMERCE: Digital Engines for the New Economy
Web Summary- Managing Files: Basic
Concepts. Data is organized in a data storage hierarchy
of increasingly complex levels: bits, bytes (characters), fields, records,
files, and databases. A character
is a letter, number, or special character. A field
consists of one or more characters (bytes). A record
is a collection of related fields. A file
is a collection of related records. A database is, as mentioned, an organized
collection of integrated files. Important to data organization is the key
field, a field used to uniquely identify a record so that it can be easily
retrieved and processed.
Files are given names—filenames.
Filenames also have extension names, three-letter additions such as .doc
and .txt. Among the types of files are the following. (1) Program files
are files containing software instructions. The two most important are source
program files, which contain instructions in the form written by the programmer,
and executable files, which contain instructions that tell a computer how
to perform a particular task. (2) Data files are files that contain data.
(3) Other common files are ASCII files, which are text only; image files
for digitized graphics; audio files, which contain digitized sound; animation/video
files, used for conveying moving images; and Web files, which are files
carried over the World Wide Web. Two main ways in which a
storage device accesses stored data are sequential access and direct access.
Sequential storage
means that data is stored and retrieved in sequence, as is the case with
magnetic-tape storage. Direct access storage
means that a computer can go directly to the information you want, as in
a CD player; hard disks and other types of disks are of this nature. Whether on magnetic tape
or disk, data may be stored offline or online. Offline storage
means that data is not directly accessible for processing until the tape
or disk has been loaded onto an input device. Online storage
means that stored data is randomly (directly) accessible for processing.
- Database Management Systems.
A database management system
(DBMS) consists of programs that control the structure of a database and access
to the data. The benefits of databases are file sharing, reduced data redundancy,
improved data integrity, and increased security. Databases can be classified
as four types. (1) An individual database
is a collection of integrated files used by one person. It could be a personal
information manager, which helps people keep track of information they use
daily. (2) A shared database,
or company database, is shared by users in one organization in one location.
(3) A distributed database is stored on different computers in different locations
connected by a client/server network. (4) A public databank
is a compilation of data available to the public; many such databanks are
Web sites. The last three databases should have a database administrator
to coordinate activities and needs.
- Database Models. Databases
can be organized in four ways. (1) In a hierarchical database,
fields or records are arranged in related groups resembling a family tree,
with child (lower-level) records subordinate to parent (higher-level) records.
(2) A network database
is similar to a hierarchical database but each child record can have more
than one parent record. (3) A relational database
relates, or connects, data in different files through the use of a key field.
Structured query language
is an easy-to-use computer language for making queries to a relational database
and for retrieving selected records. One feature of most query languages is
query by example
(QBE), which allows users to ask for information in a relational database
by using a sample record to define the qualifications they want for selected
records. (4) An object-oriented database
uses objects, software written in small, reusable chunks, as elements within
database files. An object consists of data in any form and instructions on
the action to be taken on the data.
- Features of a Database
Management System. A database management system may have a number of components.
(1) A data dictionary
is a procedures document or disk file that stores the data definitions or
a description of the structure of data used in the database. (2) DBMS utilities
are programs that allow you to maintain the database by creating, editing,
and deleting data, records, and files. (3) A report generator
is a program for producing an onscreen or printed document from all or part
of a database. (4) Different users are given different user access privileges,
as determined by the database administrator. (5) A DBMS should have system
recovery features, so the database administrator can recover the contents
of the database in the event of hardware or software failure. Four approaches
are: mirroring, with two copies of the database in different locations; reprocessing,
in which the processing can be redone from a known past point; rollforward,
a variant on reprocessing; and rollback, which is used to undo unwanted changes
to the database.
- Databases & the New
Economy: E-Commerce, Data Mining, & B2B Systems. Databases underpin
the so-called New Economy of computer, telecommunications, and Internet companies
in three ways: e-commerce, data mining, and business-to-business (B2B) systems.
E-commerce,
or electronic commerce, is the buying and selling of products and services
through computer networks; an example is Amazon.com. Data mining
is the computer-assisted process of sifting through and analyzing vast amounts
of data in order to extract meaning and discover new knowledge. Data mining
begins with acquiring data and cleaning it of errors to yield cleaned-up
data and a version of it called meta-data (which shows its origins and transformations),
which are then sent to a data warehouse,
a special database of cleaned-up data and meta-data. Three kinds of tools
are used to perform data mining, or finding and analyzing tasks: query and
reporting tools, multidimensional-analysis tools, and intelligent agents.
Data mining is used in applications ranging from marketing to health to
science. Business-to-business systems
(B2B systems) allow businesses to sell to other businesses, using the Internet
or private network to cut transaction costs and increase efficiencies. - The Ethics of Using Databases:
Concerns about Accuracy & Privacy. In morphing,
a film image is altered pixel by pixel, so that the image becomes something
else. This manipulation of digitized images and sounds raises some ethical
issues. Sound performances can be misrepresented, photos may be manipulated,
and video and TV images may be altered in undetectable ways and all stored
in a database.
Databases are also limited
in accuracy and completeness, since not all facts can be found in a database,
nor are all data items true. In addition, databases raise several concerns
about privacy. Finally, those who own databases may be in a position to
monopolize information.
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2002 McGraw-Hill Higher Education