isa / isa!
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This documentation is not current - it is for TypeDB 2.x, which is no longer supported. View the documentation for TypeDB 3.x: |
The isa keyword is used in TypeQL to specify a type for data instances, taking into account type inference.
For specifying only a direct type with no subtypes, use the isa! keyword instead.
Syntax
The syntax of an isa or isa! statement includes:
-
Subject — a concept variable representing a data instance
-
Predicate — the
isa/isa!keyword -
Object — a type label or concept variable representing a type
<concept-variable> isa <type>;Behavior
TypeQL statements with the isa and isa! keyword are used in data queries and rules.
The isa keyword adds a constraint of a type, including all subtypes, to data instances,
represented by a concept variable.
The isa! keyword does the same, but excludes the subtypes.
Usage in a match pattern
For this example, use a database with the IAM schema and sample data loaded.
In a match clause pattern an isa statement can be used to match data instance of a selected type
or any of its subtype (via type inference).
For example, let’s match and fetch all data instances of type full-name from a database:
match
$name isa full-name;
fetch $name;See example output
{ "name": { "value": "Masako Holley", "type": { "label": "full-name", "root": "attribute", "value_type": "string" } } }
{ "name": { "value": "Kevin Morrison", "type": { "label": "full-name", "root": "attribute", "value_type": "string" } } }
{ "name": { "value": "Pearle Goodman", "type": { "label": "full-name", "root": "attribute", "value_type": "string" } } }Now let’s match all attributes in a database by using an isa statement with the attribute root type:
match
$attr isa attribute;
fetch $attr;See example output
{ "attr": { "value": 1705, "type": { "label": "size-kb", "root": "attribute", "value_type": "long" } } }
{ "attr": { "value": "kevin.morrison@typedb.com", "type": { "label": "email", "root": "attribute", "value_type": "string" } } }If you switch the isa keyword to the isa! you get no results,
because there can be no data instances for the abstract root type, and subtypes are ignored by the isa!:
match
$attr isa! attribute;
fetch $attr;Usage in an insert pattern
For this example, use a database with the IAM schema and sample data loaded.
To insert a data instance to a database, you need to use an isa statement in an insert clause.
For example:
insert
$p isa person, has full-name "Bob Fake";The object must be the exact type of the instance you are inserting.
In an insert clause, the isa keyword has no difference from the isa! keyword.
When inserting an attribute, you can provide a value with a value assignment syntax:
insert
$f "John Smith" isa full-name;When inserting a relation, you can provide role players for every role with a role assignment syntax:
match
$p isa person, has full-name "Bob Fake";
insert
$per(subject: $p) isa permission;Usage in a delete pattern
For this example, use a database with the IAM schema and sample data loaded.
To delete a data instance from a database, you need to match it to a concept variable with a match clause,
and then use the concept variable with an isa statement in a delete clause of the same query.
For deleting, you can use the exact type of the data instance or any of its supertypes, including a root type.
Let’s delete
match
$p isa person, has full-name "Bob Fake";
delete
$p isa person;Using isa! in a delete clause requires us specify the exact type of the data instance to delete.
So, using any of its supertypes, including a root type, should fail:
match
$f "John Smith" isa full-name;
delete
$f isa! attribute;To use a supertype, switch back to the isa keyword:
match
$f "John Smith" isa full-name;
delete
$f isa attribute;