Glossary

May 2024 · 6 minute read
Glossary

Previous Topic: Classification of Dependent Entities

alternate key

An attribute or attributes that uniquely identify an instance of an entity.

If more than one attribute or group of attributes uniquely identify an instance of an entity, the alternate keys are those attributes or groups of attributes not selected as the primary key. A unique index for each alternate key is generated.

attribute

Represents a type of characteristic or property associated with a set of real or abstract things (people, places, events, and so on).

basename

The original name of a rolenamed foreign key.

binary relationship

A relationship where exactly one instance of the parent is related to zero, one, or more instances of a child. In IDEF1X, identifying, non-identifying, and subtype relationships are all binary relationships.

BLOB

A dbspace that is reserved for storage of the byte and text data that makes up binary large objects, or BLOBs, stored in table columns. The BLOB dbspace can hold images, audio, video, long text blocks, or any digitized information.

cardinality

The ratio of instances of a parent to instances of a child. In IDEF1X, the cardinality of binary relationships is 1:n, where n can be one of the following:

complete subtype cluster

If the subtype cluster includes all of the possible subtypes (every instance of the generic parent is associated with one subtype), then the subtype cluster is complete. For example, every ACCOUNT is either a checking, savings, or loan account and therefore the subtype cluster of CHECKING‑ACCOUNT, SAVINGS-ACCOUNT, or LOAN-ACCOUNT is a complete subtype cluster.

dependent entity

An entity whose instances cannot be uniquely identified without determining its relationship to another entity or entities.

denormalization

To allow data redundancy in a table to improve query performance.

discriminator

The value of an attribute in an instance of the generic parent determines to which of the possible subtypes that instance belongs. This attribute is known as the discriminator. For example, the value in the attribute “account-type” in an instance of ACCOUNT determines to which particular subtype (CHECKING‑ACCOUNT, SAVINGS-ACCOUNT, or LOAN-ACCOUNT) that instance belongs.

domain

A group of predefined logical and physical property characteristics that can be saved, selected, and then attached to attributes and columns.

entity

An entity represents a set of real or abstract things (people, places, events, and so on) that have common attributes or characteristics. Entities can be either independent or dependent.

foreign key

An attribute that has migrated through a relationship from a parent entity to a child entity. A foreign key represents a secondary reference to a single set of values; the primary reference is the owned attribute.

identifying relationship

A relationship where an instance of the child entity is identified through its association with a parent entity. The primary key attributes of the parent entity become primary key attributes of the child.

incomplete subtype cluster

If the subtype cluster does not include all of the possible subtypes (every instance of the generic parent is not associated with one subtype), then the subtype cluster is incomplete. For example, if some employees are commissioned, a subtype cluster of SALARIED-EMPLOYEE and PART-TIME EMPLOYEE is incomplete.

independent entity

An entity whose instances can be uniquely identified without determining its relationship to another entity.

inversion entry

An attribute or attributes that do not uniquely identify an instance of an entity, but are often used to access instances of entities. A non-unique index for each inversion entry is generated.

logical model

The data modeling level where you create a conceptual model that contains objects such as entities, attributes, and key groups.

logical/physical model

A model type created where the logical and physical models are automatically linked.

non-key attribute

Any attribute that is not part of the entity’s primary key. Non-key attributes can be part of an inversion entry or alternate key, and can also be foreign keys.

non-identifying relationship

A relationship where an instance of the child entity is not identified through its association with a parent entity. The primary key attributes of the parent entity become non-key attributes of the child.

non-specific relationship

Both parent-child connection and subtype relationships are considered specific relationships since they define precisely how instances of one entity relate to instances of another. However, in the initial development of a model, it is often helpful to identify non-specific relationships between two entities. A non-specific relationship, also referred to as a many-to-many relationship, is an association between two entities where each instance of the first entity is associated with zero, one, or many instances of the second entity and each instance of the second entity is associated with zero, one, or many instances of the first entity.

normalization

The process by which data in a relational construct is organized to minimize redundancy and non-relational constructs.

physical model

The data modeling level where you add database and database management system (DBMS) specific modeling information such as tables, columns, and datatypes.

primary key

An attribute or attributes that uniquely identify an instance of an entity. If more than one attribute or group of attributes can uniquely identify each instance, the primary key is chosen from this list of candidates based on its perceived value to the business as an identifier. Ideally, primary keys should not change over time and should be as small as possible. A unique index for each primary key is generated.

referential integrity

The assertion that the foreign key values in an instance of a child entity have corresponding values in a parent entity.

rolename

A new name for a foreign key. A rolename is used to indicate that the set of values of the foreign key is a subset of the set of values of the attribute in the parent, and performs a specific function (or role) in the entity.

schema

The structure of a database. Usually refers to the DDL (data definition language) script file. DDL consists of CREATE TABLE, CREATE INDEX, and other statements.

specific relationship

A specific relationship is an association between entities where each instance of the parent entity is associated with zero, one, or many instances of the child entity, and each instance of the child entity is associated with zero or one instance of the parent entity.

subtype entity

There are often entities which are specific types of other entities. For example, a SALARIED EMPLOYEE is a specific type of EMPLOYEE. Subtype entities are useful for storing information that only applies to a specific subtype. They are also useful for expressing relationships that are only valid for that specific subtype, such as the fact that a SALARIED EMPLOYEE qualifies for a certain BENEFIT, while a PART-TIME-EMPLOYEE does not. In IDEF1X, subtypes within a subtype cluster are mutually exclusive.

subtype relationship

A subtype relationship (also known as a categorization relationship) is a relationship between a subtype entity and its generic parent. A subtype relationship always relates one instance of a generic parent with zero or one instance of the subtype.

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