GLOSSARY - Concepts of Database Management - page 399

GLOSSARY

Access delay A fixed amount of time required for every
message sent over a network.
After image A record that the DBMS places in the
journal or log that shows what the data in a row looked
liked in the database after a transaction update.
Aggregate function A function used to calculate the
number of entries, the sum or average of all the entries
in a given column, or the largest or smallest of the
entries in a given column; also called function.
ALTER TABLE The SQL command that is used to
change the structure of a table.
Alternate key A candidate key that was not chosen to
be the primary key.
AND criterion Combination of criteria in which both
criteria must be true.
Apache HTTP Server A free, open-source Web server
package that runs with most operating systems.
Application server In a three-tier client/server
architecture, a computer that performs the business
functions and serves as an interface between clients
and the database server.
Application software The programs that directly
support an information system in processing data to
produce the required information.
Archive See data archive.
Argument Additional information required by an action
in a data macro to complete the action.
Artificial key A column created for an entity to serve
solely as the primary key and that is visible to users.
Association A relationship in UML.
Attribute A characteristic or property of an entity; also
called a field or column.
Authentication A technique for identifying the person
who is attempting to access a DBMS.
Authorization rule A rule that specifies which user has
what type of access to which data in a database.
B2B See business to business.
Back-end machine See server.
Back-end processor See server.
Backup A copy of a database made periodically; the
backup is used to recover the database when it has been
damaged or destroyed. Also called a save.
Backward recovery See rollback.
Batch processing The processing of a transaction file
that contains a group, or

Binary large object (BLOB) A generic term for a special
data type used by relational DBMSs to store complex
objects.
Binding The association of operations to actual program
code.
Biometrics A technique to identify users of a database
or other resource by physical characteristics such as
fingerprints, voiceprints, handwritten signatures, and
facial characteristics.
BLOB See binary large object.
Bottom-up design method A design method in
which specific user requirements are synthesized into
a design.
Boyce-Codd normal form (BCNF) A relation is in
Boyce-Codd normal form if it is in second normal form
and the only determinants it contains are candidate
keys; also called third normal form in this text.
Business to business (B2B) E-commerce between
businesses.
Calculated field See computed field.
Candidate key A minimal collection of columns (attri-
butes) in a table on which all columns are functionally
dependent but that has not necessarily been chosen as
the primary key.
Cardinality The number of items that must be included
in a relationship. Also called multiplicity.
Cartesian product The table obtained by concatenating
every row in the first table with every row in the second
table.
Cascade delete A delete option in which related records
are automatically deleted.
Cascade update An update option in which related
records are automatically updated.
Catalog A source of data, usually stored in hidden
database tables, about the types of entities, attributes,
and relationships in a database.
Category The IDEF1X name for an entity subtype.
CHAR(n) The SQL data type for character data.
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.

“ batch, ” of records to update a

database or another file.
Before image A record that the DBMS places in the
journal or log that shows what the data in a row looked
like in the database before a transaction update.