Database Modeling and Design

232 Glossary
X and A are either simple or composite attributes (data items), X
must be a superkey in that table. This is a strong form of 3NF and
is the basis for most practical normalization methodologies.
candidate key—Any subset of the attributes (data items) in a superkey
that is also a superkey and is not reducible to another superkey.
CASE tool—Computer-aided software engineering tool, a software
design tool to assist in the logical design of large or complex databases.
examples include ERwin Data Modeler and Rational Rose
using UML.
class—A concept in a real-world system, represented by a noun in UML;
similar to an entity in the ER model.
class diagram (UML)—A conceptual data model; a model of the static
relationships between data elements of a system (similar to an ER
diagram).
completeness constraint—Double-line symbol connecting a supertype
entity with the subtypes to designate that the listed subtype
entities represent a complete set of possible subtypes.
composition—A relationship between one class and a group of other
classes in UML; the class at the diamond (aggregate) end of the
relationship is composed of the class(es) at the small (component)
end; similar to aggregation in the ER model.
conceptual data model—An organization of data that describes the
relationships among the primitive data elements. For example, in
the ER model, it is a diagram of the entities, their relationships,
and their attributes.
connectivity of a relationship—A constraint on the count of the
number of associated entity occurrences in a relationship, either
one or many.
data item—The basic component of a data record in a file or database
table; the smallest unit of information that has meaning in the
real world. Examples include customer lastname, address, and
identification number.
data model—An organization of data that describes the relationships
among primitive and composite data elements.
data warehouse—A large repository of historical data that can be integrated
for decision support.
database—A collection of interrelated stored data that serves the needs
of multiple users; a collection of tables in the relational model.