 
 -- node annotations
 -- unique combinantion of node_ref, namespace and name
+DROP TABLE IF EXISTS _node_annotation;
 CREATE TABLE _node_annotation
 (
 	node_ref	numeric(38)	NOT NULL,		-- foreign key to _node.id


-- corpus annotations
-- unique combinantion of corpus_ref, namespace and name
CREATE TABLE _corpus_annotation
(
	corpus_ref	numeric(38) NOT NULL,		-- foreign key to _corpus.id

-- connected components of the annotation graph
-- are of a type: Coverage, Dominance, Pointing relation or NULL for root nodes
-- have a name
DROP TABLE IF EXISTS _component;
CREATE TABLE _component
(
	id			numeric(38) NOT NULL,		-- primary key
