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SQLa Concepts


In SQL, a domain refers to a specific set of allowed values that a column (field) can have in a database table. It defines the possible values for a certain data type, which may also include constraints like NOT NULL, CHECK, DEFAULT, etc. This concept is closely related to the notion of data types and constraints.

Attribute or Property

attribute or property refers to a named instance of a specific domain. For example, person_id can be a domain but once it’s a named column of a table it becomes an attribute or a property.


entity is a concrete instance of a group of domain instances such as attributes or properties. An entity is usally a table in SQL but might also be represented as a view or a stored function.

link is a 1:n , n:1, or n:n relationship between entities.

  • Links are typically defined as foreign keys in SQL but could be represented as arrays in stored procedures or an ORM.
  • For example, if you had an Order entity (table) with order line and customer table foreign keys then the Order’s links could be 1:n items[] and 1:1 customer.


namespace refers to physical storage grouping (e.g. schemas in some databases).

Information Model Module (IMM)

information model module (IMM) is a logical grouping of multiple domains, entities, tables, views, schemas, namespaces, etc.