An entity type models a concept by means of attributes. The
ent element describes an entity type
of an entity-relationship schema. It can contain text that describe informally its
use or meaning, and any number of
A restricted identifier for this entity type.
A label for this entity type. The user will be always presented with this label when dealing with entities of this type.
This field can be set to true or false (the default). In the first case, the entity type is declared to be abstract (see the Section called Subtyping in the Chapter called Overall System Design).
This field can be set to true or false (the default). In the first case, for every entity of this type there is a user who holds all privileges about the element (i.e., you have element-based authorisation); moreover, each element can be assign to a group, and then all users belonging to the group hold all privileges about the element (the amount of privileges, however, can be controlled; see the Section called The Authorisation System in the Chapter called Authentication and Authorisation). There are some restrictions on the entity types for which this attribute can be set to true—see the Section called Restrictions on Element-Based Authorisation in the Chapter called Authentication and Authorisation.
An entity type is always reified by an SQL table named as the
id and having as
columns the reification of its attributes. Note however that because
of virtual types the reification of an entity type may in fact create
several SQL tables, namely those for dynamic enumerative attributes
and those for filesets. Additional columns may also appear in the
reification of an entity type if relationship types have been
absorbed into it.
Note that when you require element-based authorisation you are also requiring it for all subtypes. For this reason, to avoid inconsistencies only certain entity types can have element-based authorisation. See the Section called Restrictions on Element-Based Authorisation in the Chapter called Authentication and Authorisation.