GLOSSARY - Concepts of Database Management - page 366

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CHECK The SQL clause that is used to enforce legal-
values integrity.
Class The general structure and actions of an object
in an object-oriented system.
Class diagram A UML diagram that for each class,
shows the name, attributes, and methods of the class,
as well as the relationships between the classes in a
database.
Client A computer that is connected to a network
and that people use to access data stored on a server
in a client/server system; also called a front-end
machine or a front-end processor.
Client/server A networked system in which a special
site on the network, called the server , provides ser-
vices to the other sites, called the clients . Clients send
requests for the specific services they need. Software,
often including a DBMS, running on the server then
processes the requests and sends only the appropriate
data and other results back to the clients.
Client-side extension Instructions executed by a
Web client to provide dynamic Web page capability.
These extensions can be embedded in HTML docu-
ments or be contained in separate files that are refer-
enced within an HTML document.
Client-side script See client-side extension.
Column A characteristic or property of an entity;
also called an attribute or a field.
Command An instruction by a user that directs a
database to perform a certain function.
Commit A special record in a database journal or log
that indicates the successful completion of a
transaction.
Communications network Several computers config-
ured in such a way that data can be sent from any one
computer on the network to any other. Also called a
network .
Comparison operator See relational operator.
Complete category In IDEF1X, a collection of sub-
types with the property that every element of the
supertype is an element of at least one subtype.
Composite entity An entity in the entity-relationship
model used to implement a many-to-many
relationship.
Compound condition See compound criteria .

Compound criteria Two simple criteria (conditions)
in a query that are combined with the AND or OR
operators.
Computed field See calculated field .
Concatenation The combination of columns. To say
a primary key is a concatenation of two columns
means that a combination of values in both columns is
required to uniquely identify a given row.
Concurrent update A situation when multiple users
make updates to the same database at the same time.
Condition See criterion .
Context-sensitive help The assistance a DBMS pro-
vides for the particular feature being used at the time
a user asks for help.
Cookies Small files written on a Web client's hard
drive by a Web server.
Coordinator In a distributed network, the site that
directs the update to the database for a transaction.
Often, it is the site that initiates the transaction.
CREATE INDEX The SQL command that creates an
index in a table.
CREATE TABLE The SQL command used to
describe the layout of a table. The word TABLE is fol-
lowed by the name of the table to be created and then
by the names and data types of the columns (fields)
that comprise the table.
Criteria The plural version of the word criterion .
Criterion A statement that can be either true or
false. In queries, only records for which the statement
is true will be included; also called a condition .
Cumulative design A design that supports all the
user views encountered thus far in a design process.
Data archive A place where a record of certain cor-
porate data is kept; also called an archive . Data that is
no longer needed in a corporate database but must be
retained for future reference is removed from the
database and placed in the archive.
Data cube The perceived shape by a user of a multi-
dimensional database in a data warehouse.
Data dictionary A catalog, usually found in large,
expensive DBMSs, that stores data about the entities,
attributes, relationships, programs, and other objects
in a database.
Data file A file used to store data about a single
entity. It's the computer counterpart to an ordinary
paper file you might keep in a file cabinet, an account-
ing ledger, and so on. Such a file can be thought of as
a table.