Glossary

Abstract Entity  An entity that models relationships between other entities.

Ad Hoc Report  A report that is configured by the user after implementation of the application.

Aggregate Function  A SQL function that returns summary values.

Alternate Key  A candidate key of a relation that is not used as the primary key of a table.

Application  The forms and reports with which the user interacts.

Attribute  A column in a relation.

Base Relation  A relation that is instantiated as a table in the database.

Binary Relationship  A relationship having two participants.

Boolean Expression  An expression that results in either True or False.

Business Constraint  A constraint derived from the problem space.

Business Rule  An integrity constraint that originates in the problem space rather than from relational theory.

Candidate Key  One or more attributes that uniquely identify a relation.

Cardinality of a Relation  The number of rows in a relation.

Cardinality of a Relationship  The maximum number of instances of one entity that can participate in a relationship.

Cartesian Product  A relational operation that combines every record in one recordset with every record in a second recordset.

Cascading Update  The automatic updating of entities in a foreign relation when the corresponding entity in the primary relation is changed.

Closure  The principle that all operations on a relation result in a relation and can be used for further manipulation.

Command Vector  A path to the execution of a command in a user interface, for example a menu item or a toolbar button.

Composite Entity  A single entity in the problem space that is modeled by one or more relations.

Composite Key  A candidate key composed of two or more attributes.

Concrete Entity  An entity that models an object or event in the real world.

Database  The combination of the database schema and the stored data.

Database Application  The forms and reports with which the user interacts.

Database Constraint  An integrity constraint that references multiple relations.

Database Schema  The physical layout of tables in a database.

Database System  The combination of the database application, database engine, and database.

Data Integrity  The rules used by a database to ensure that the data is, if not correct, at least plausible.

Data Model  The conceptual description of a problem space in relational terms.

Declarative Integrity  A method of defining integrity constraints by explicitly declaring them as part of a table definition.

Degree of a Relation  The number of columns in a relation.

Degree of a Relationship  The number of participants in a relationship.

Derived Relation  A virtual relation that is defined in terms of other relations.

Domain  The range of values from which an attribute can be drawn.

Domain Constraint  An integrity constraint that determines the range of possible values for a domain.

Entity  Anything about which the system needs to store information.

Entity Constraint  An integrity constraint that ensures the validity of the entities being modeled by the system.

Equi-Join  A join between two tables on the basis of equality.

Field  The physical representation of an attribute in a database.

Foreign Relation  The relation that receives the primary key of the other participant in a relationship.

Full Outer Join  An outer join that returns all fields from both participants.

Inner Join  A join that returns records only when the result of an operation is True.

Integrity Constraint  A data integrity rule.

Intrinsic Constraint  A constraint that governs the physical structure of the database.

Junction Table  A table that represents a relationship in the database.

Left Outer Join  An outer join that returns all fields from the first recordset listed in a SELECT statement.

Lossless Decomposition  The ability to divide relations in such a manner that they can be recombined without loss of information.

Natural Join  A special case of an equi-join in which the join is performed on the basis of equality, all common fields participate in the join, and only one set of common fields is included in the result set.

Orphan Entity  A weak entity that is not related to an entity in the primary relation of a relationship.

Outer Join  A join that returns all the records of an inner join plus all the records in either or both of the other participants.

Participant  An entity that is associated to another in a relationship.

Passive User Assistance  A user assistance mechanism that is an intrinsic part of the user interface.

Primary Key  The candidate key of a relation that is used to uniquely identify the records in a table.

Primary Relation  The relation whose primary key is stored in the other participant in a relationship.

Proactive User Assistance  A user assistance mechanism that attempts to anticipate the users' needs.

Problem Space  The portion of the real world that is to be modeled by a database application.

Procedural Integrity  A method of enforcing data integrity by creating procedures that are executed automatically when a record is updated, inserted, or deleted.

Query  A derived relation in Microsoft Access.

Reactive User Assistance  A user assistance mechanism that is triggered by some action by the user, such as an invalid entry or the request for online help.

Record  The physical representation of a tuple.

Recordset  The generic term used in Microsoft Access to mean the physical representation of a relation.

Referential Integrity  The integrity constraints that ensure that relationships between entities remain valid.

Regular Entity  An entity that can exist without participating in a relationship.

Relation  A logical construct that organizes data into rows and columns.

Relation Body  The tuples comprising a relation.

Relation Heading  The definition of the attribute and domain at the top of a relation.

Relational Difference  A relational operation that returns the records of one recordset that are not matched in another recordset.

Relational Divide  A join that returns all the records in one recordset that have values that match all the corresponding values in the second recordset.

Relational Intersection  A relational operation that returns the records two recordsets have in common.

Relational Union  The concatenation of two recordsets.

Relationship  An association between two or more entities.

Right Outer Join  An outer join that returns all fields from the second recordset listed in a SELECT statement.

Scalar Value  A single, nonrepeating value.

Schema  The physical layout of tables in a database system.

Simple Key  A candidate key composed of a single attribute.

Standard Report  A report that can be defined and implemented as part of the database application.

Table  The physical instantiation of a relation in the database schema.

Task  A discrete step in a work process.

Ternary Relationship  A relationship having three participants.

Theta-Join  Technically, any join based on a comparison operator, but normally restricted to joins based on operators other than equality.

Three-Valued Logic  A model for logical evaluation that allows the values True, False, and Null as results of expressions.

Transaction Integrity  An integrity constraint that controls the validity of multiple operations on the database.

Tuple  A row in a relation.

Type-Compatible Domains  Domains that can be logically compared.

Unary Relationship  An association between a relation and itself.

Update Anomaly  Problems with data manipulation resulting from a poorly designed data model.

View  A derived relation in SQL Server.

Weak Entity  An entity that can exist only if it participates in a given relationship.

Work Process  Something that is to be done using the database application.