Boolean

#!test[schema]
define
  attribute shipped value boolean;

#!test[schema]
#{{
define
  entity order, owns shipped;
#}}
#!test[write]
insert
  $o isa order, has shipped false;

#!test[write]
insert
  $_ isa shipped false;

#!test[schema]
define
  attribute opted-in value boolean @values(true);

#!test[schema]
#{{
define
  attribute email-verified value boolean;
#}}
#!test[schema]
define
  entity subscriber owns email-verified @values(true);

#!test[read]
match
  $o isa order, has shipped false;