Delete stage

A delete stage deletes data from the database. Deletable data includes instances of types, ownerships of attributes, and role players of relations.

Syntax

The body of a delete stage is a sequence of delete statements.

delete ( <variable> | has <variable> of <variable> | links ( <variable> [ , ... ] ) of <variable> ); [ ... ]

Behavior

Bare variables delete the instances they refer to from the database.
Delete has statements delete ownerships of attributes.
Delete links statements delete role players from relations.

Execution

The delete stage must be preceded by other stages. The body of the delete stage is executed once for each input row. The output is then a stream of input rows with the deleted concepts removed.

Example

match
  $person isa person, has name "<name>";
  $group isa group, has group-id "<group id>";
  $membership isa group-membership(group: $group, member: $person) has rank $rank;
  $rank == "member";
delete
  has $rank of $membership;
  links ($person) of $membership;
  $group;