user interface is housed on the client, usually a PC (tier 1); the
processing is performed on a midrange system operating as the
applications server (tier 2); and the data are stored on a large
machine (often a mainframe or midrange system) that operates
as the database server (tier 3).
Timeboxing Establishing a maximum time limit for the
delivery of a project or project module; typically 6 months or less.
Token bus A design standard for a local area network based on
a bus topology and the passing of a token around the bus to all
devices in a specified order. In this design, a given device can
only transmit when it has the token and thus collisions can never
occur. The token bus design is central to the Manufacturing
Automation Protocol (MAP).
Token ring A design standard for a local area network based
on a ring topology and the passing of a token around the ring
to all devices in a specified order. In this design, a given device
can only transmit when it has the token and thus collisions can
never occur.
Total cost of ownership (TCO) Total cost of ownership for a
computer system or device, including initial purchase or develop-
ment costs, initial implementation costs, as well as ongoing
support costs. For example, the TCO for a desktop PC includes
not only the purchase and installation of the PC hardware and the
software and network installation costs but also the cost of sup-
porting the use of the PC (e.g., user training, help desk, software
upgrades, file storage backup, and IT-related investments).
Transaction processing system A very common type of
computer application in which transactions (of a particular type)
are processed in order to provide desired output. Examples
include the processing of employee work records (transactions)
to produce payroll checks and accompanying reports and the
processing of orders (transactions) to produce invoices and asso-
ciated reports. Transaction processing systems might be batch,
online, or in-line.
Transborder data flow Electronic movement of data across a
country’s national boundary. Such data flows may be restricted
by laws that protect a country’s economic, political, or personal
privacy interests.
Transmission Control Protocol/Internet Protocol (TCP/IP)
A popular network protocol used in the Internet, as well as in
intranets operating within organizations and many packet-
switched networks. Although not part of the OSI model, TCP/IP
corresponds roughly to the network and transport layers of the
seven-layer model.
Tree topology A network topology that has some primary
device at the top of the tree, with cables radiating from this
primary device to devices further down the tree that, in turn, may
have cables radiating from them to other devices still further
down the tree, and so on; also called hierarchical topology.
Twisted pair The most common transmission medium, with two
insulated copper wires (about 1 millimeter thick) twisted together
in a long helix. Data transmission speeds up to 56,000 bits per
second (bps) are possible with twisted pairs on the analog tele-
phone network, with higher speeds of 128,000 bps up to 24 million
bps attainable over a digital telephone line or up to 100 billion bps
on local area networks.
Twitter A social networking and microblogging application
that enables its users to send and read messages known as tweets;
tweets are text-only messages of up to 140 characters that are
posted on the author’s Twitter page and delivered to the author’s
subscribers, who are known as followers.
Two-tier client/server system The original implementation of
a client/server system in which the processing is split between the
client (usually a PC) and the server (midrange system or
mainframe). If most of the processing is done on the client, this is
called a fat client or thin server model; if most of the processing
is done on the server, this is called a thin client or fat server
model.
UC SeeUnified communications.
UML SeeUnified Modeling Language.
Unified communications (UC) UC, the newest buzzword in
office automation, is the integration of real-time communication
services, such as telephony and IM, with non–real-time commu-
nication services, such as e-mail, voicemail, and facsimile. With
UC, an individual can send a message on one medium and have it
read on another medium.
Unified Modeling Language (UML) A general-purpose nota-
tional system for specifying and visualizing complex software,
especially large, object-oriented projects. Examples of such
UML-based CASE tools are IBM’s Rational Rhapsody and
Borland’s Together.
Universal Resource Locator (URL) An address for an
Internet file; the address includes the name of the protocol to
access the resource (usually http), a domain name for the com-
puter on which the file is located, and perhaps specific locator
information. For example, the Web URL for the publisher of this
textbook is http://www.prenhall.com. Also known as Uniform
Resource Locator.
URL SeeUniversal Resource Locator.
Usenet newsgroups An Internet application, or tool, setting up
discussion groups, which are essentially huge electronic bulletin
boards on which group members can read and post messages.
User computing Hands-on use of computer resources by
workers who are not IS specialists to enter data, make data
queries, prepare reports, communicate, perform statistical analyses,
analyze problems, navigate online applications, develop Web
pages, and so forth.
User interface That part of a system through which the user
interacts with the system. As examples, it may use a mouse, a
touch-screen, menus, commands, voice recognition, a telephone
keypad, output screens, voice response, and printed reports. See
alsoGraphical user interface.
Value added network (VAN) Formerly, the name given to the
practice of contracting with an outside vendor to operate a
packet-switched wide area network (WAN) for an organization.
Today such a packet-switched WAN is usually called a managed
network.688 Glossary