GLOSSARY - Concepts of Database Management - page 402

Entity A person, place, object, event, or idea for which
you want to store and process data.
Entity integrity The rule that no column (attribute) that
is part of the primary key may accept null values.
Entity subtype Entity A is a subtype of entity B if every
occurrence of entity A is also an occurrence of entity B.
Entity-relationship (E-R) diagram A graphic model for
database design in which entities are represented as
rectangles and relationships are represented as either
arrows or diamonds connected to the entities they relate.
Entity-relationship (E-R) model An approach to
representing data in a database that uses E-R diagrams
exclusively as the tool for representing entities,
attributes, and relationships.
Exclusive lock A lock that prevents other users from
accessing the locked data in any way.
Existence dependency A relationship in which the
existence of one entity depends on the existence of
another related entity,
Extensible The capability of defining new data types in
an OODBMS.
Extensible Hypertext Markup Language See XHTML.
Extensible Markup Language See XML.
Extensible Stylesheet Language See XSL.
Fact table The central table in a data warehouse that
consists of rows that contain consolidated and summa-
rized data.
Fat client In a two-tier client/server architecture, a cli-
ent that performs presentation functions and business
functions.
Field A characteristic or property of an entity; also
called an attribute or a column.
File server A networked system in which a special site
on the network stores files for users at other sites. When
a user needs a file, the file server sends the entire file to
the user.
First normal form (1NF) A table is in first normal form
if it does not contain a repeating group.
Foreign key A column (attribute) or collection of col-
umns in a table whose value is required either to match
the value of a primary key in a table or to be null.
FOREIGN KEY The clause in a SQL CREATE TABLE
or ALTER TABLE command that specifies referential
integrity.
Form A screen object you use to maintain, view, and
print data from a database.
Forward recovery A process used to recover a database
by reading the log and applying the after images of
committed transactions to bring the database up to date.
Fourth normal form (4NF) A table is in fourth normal
form if it is in third normal form and there are no mul-
tivalued dependencies.
Fragmentation transparency The characteristic that
users do not need to be aware of any data fragmentation

(splitting of data) that has taken place in a distributed
database.
FROM clause The part of an SQL SELECT command
that indicates the tables in the query.
Front-end machine See client.
Front-end processor See client.
Function See aggregate function.
Functional dependence See functionally dependent.
Functionally dependent Column B is functionally depen-
dent on column A (or on a collection of columns) if a value
for A determines a single value for B at any one time.
Functionally determines Column A functionally deter-
mines column B if B is functionally dependent on A.
Generalization In UML, the relationship between a
superclass and a subclass.
Global deadlock In a distributed database, deadlock
that cannot be detected solely at any individual site.
GRANT The SQL statement that is used to grant
different types of privileges to users of a database.
GROUP BY clause The part of an SQL SELECT
command that indicates grouping.
Grouping The process of creating collections of records
that share some common characteristic.
Growing phase A phase during a database update in
which the DBMS locks all the data needed for a
transaction and releases none of the locks.
HAVING clause The part of an SQL SELECT command
that restricts the groups to be displayed.
Heterogeneous DDBMS A distributed DBMS in which
at least two of the local DBMSs are different from each
other.
HIPAA (Health Insurance Portability and Accountabil-
ity Act) A federal law enacted in 1996 that specifies the
rules for storing, handling, and protecting health-care
transactions.
Homogeneous DDBMS A distributed DBMS in which all
the local DBMSs are the same.
Hot site A backup site that an organization can switch
to in minutes or hours because the site is completely
equipped with duplicate hardware, software, and data
that the organization uses.
HTML (Hypertext Markup Language) A language used
to create Web pages and derived from SGML.
HTTP (Hypertext Transfer Protocol) The data
communication method used by Web clients and Web
servers to exchange data on the Internet.
Hyperlink A tag in a Web page that links one Web page to
another or links to another location in the same Web page.
Hypertext Markup Language See HTML.
Hypertext Transfer Protocol See HTTP.
IDEF1X A type of E-R diagram; or, technically, a lan-
guage in the IDEF (Integrated Definition) family of lan-
guages that is used for data modeling.

402