Entities are used to define the structure of your data |
An entity is defined by a set of properties (Attributes) and can either be of a physical or conceptual nature. Examples of possible entities: Customer, Employee, Policy, House, Car, Driver, Call, Incident, Product etc.
Tip: The name of an entity should be singular. |
In the runtime, entities take shape in the form of an Instance.
Take for example an application for managing a queue. The entity Person has several Attributes, such as Name and BirthDate. Multiple persons can be entered into the application, which means that there can also be multiple instances of the entity Person.
The application only handles one queue at a time, so there is also an entity Queue, of which there is only one instance. This is called a "singleton".
Please see the documentation on Instance for further information.
Entities can be defined in terms of an existing entity by starting with the base entity's definition and adding to it. This principle is called inheritance. By selecting a base-entity while creating a new entity, the latter will inherit all attributes and relations of the base-entity. These inherited attribute definitions cannot be changed. Additional attributes can be added to the entity's definition.
An entity can be made abstract, in which case no instances can be created of this entity. Other entities can inherit attributes from this abstract entity, and these entities can be instantiated (if they are not abstract).
If the abstract class is also singleton, then it can only be used as base entity for singleton entities. Otherwise, it can be used by both singleton and multiton entities.
An attribute within an abstract entity cannot be used on a page.