GLOSSARY - Concepts of Database Management - page 368

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Distributed database management system
(DDBMS) A DBMS capable of supporting and
manipulating distributed databases.
Division The relational algebra command that com-
bines tables and searches for rows in the first table
that match all rows in the second table.
Document Type Definition (DTD) A set of state-
ments that specifies the elements (tags), the attributes
(characteristics associated with each tag), and the ele-
ment relationships for an XML document. The DTD
can be a separate file with a .dtd extension, or you can
include it at the beginning of an XML document
Documenter An Access tool that prints documenta-
tion about the objects in a database.
Domain The set of values that are permitted for an
attribute.
Drill down The process of viewing and analyzing
lower levels of aggregation, or a more detailed view of
the data.
DROP INDEX The SQL command that drops
(deletes) an index from a table.
DROP TABLE The SQL command that drops
(deletes) a table from a database.
DTD See Document Type Definition .
Dynamic Web page A Web page whose content
changes in response to the different inputs and
choices made by Web clients.
E-commerce See electronic commerce .
Electronic commerce (e-commerce)

Entity-relationship (E-R) model An approach to rep-
resenting 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
client that performs presentation functions and busi-
ness 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 An column (attribute) or collection of
columns 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 ref-
erential integrity.
Form A screen object you use to maintain, view, and
print data from a database.
Forward recovery A process used to recover a data-
base 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 nor-
mal form if it is in third normal form and there are no
multivalued dependencies.
Fragmentation transparency The characteristic that
users do not need to be aware of any data fragmenta-
tion (splitting of data) that has taken place in a dis-
tributed database.

Business con-

ducted on the Internet and Web.
Encapsulated In an object-oriented system, defining
an object to contain both data and its associated
actions.
Encryption A security measure that converts the
data in a database to a format that's indecipherable to
normal programs. The DBMS decrypts, or decodes, the
data to its original form for any legitimate user who
accesses the database.
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.