Annotations
Introduction
Annotations are useful language constructs that begin with an @.
They can be used to enforce constraints on definitions.
Syntax
Annotations are applied to the latest statement before their declaration:
<type label> @annotation;<type label> value <value type> @annotation;<type label> plays <role type label> @annotation;Arguments
Some annotations accept arguments of different types:
@annotation(5)
@annotation("TypeDB!")@annotation(0, 1, 2, 3, 4, 5)
@annotation("Welcome", "to", "TypeDB", "!")@annotation(0..10)
@annotation("a".."z")
@annotation(1..)Combining with other statements
Annotation definition is a regular statement and can be followed by other statements after a comma:
<type label> @annotation, value <value type> @annotation, plays <role type label> @annotation;However, it is possible to chain multiple annotations for a single statement:
<type label> @annotation1 @annotation2 @annotation3;Which is an equivalent of:
<type label> @annotation1;
<type label> @annotation2;
<type label> @annotation3;Behavior
It is possible to define an unlimited number of annotations of different kinds for a type.
However, only one definition of a specific kind of annotation can exist for a type at a time (e.g., @a(X) and @a(Y) cannot co-exist in the schema).
-
Defining
@awhile@bis already defined results in both@aand@bbeing defined (with a couple of exceptions like@keyand@unique). -
Defining
@awhen@ais already defined makes no changes. -
Defining
@a(x)when@a(y)is already defined replaces@a(y)with@a(x).