Database Modeling and Design

Glossary 233
database administrator (DBA)—The person in a software organization
who is in charge of designing, creating, and maintaining the
databases of an enterprise. The DBA makes use of a variety of software
tools provided by a DBMS.
database life cycle—An enumeration and definition of the basic steps
in the requirements analysis, design, creation, and maintenance
of a database as it evolves over time.
database management system (DBMS)—A generalized software
system for storing and manipulating databases. Examples include
Oracle, IBM’s DB2, Microsoft SQL Server, or Access.
data mining—A way of extracting knowledge from a database by
searching for correlations in the data and presenting promising
hypotheses to the user for analysis and consideration.
DBA—See database administrator.
degree of a relationship—The number of entities associated in the
relationship: recursive binary (1 entity), binary (2 entities), ternary
(3 entities), n-ary (n entities).
denormalization—The consolidation of database tables to increase
performance in data retrieval (query), despite the potential loss of
data integrity. Decisions on when to denormalize tables are based
on cost/benefit analysis by the DBA.
deployment diagram (UML)—Shows the physical nodes on which a
system executes. This is more closely associated with physical
database design.
dimension table—The smaller tables used in a data warehouse to
denote the attributes of a particular dimension, such as time, location,
customer characteristics, product characteristics, etc.
disjointness constraint (d)—A symbol in an ER diagram to designate
that the lower-level entities in a generalization relationship have
nonoverlapping (disjoint) occurrences. If the occurrences overlap,
then use the designation (o) in the ER diagram.
entity—A data object that represents a person, place, thing, or event if
informational interest; it corresponds to a record in a file when
stored. For example, you could define employee, customer,
project, team, and department as entities.
entity cluster—The result of a grouping operation on a collection of
entities and relationships in an ER model to form a higher-level
abstraction, which can be used to more easily keep track of the
major components of a large-scale global schema.