Table inherit & foreign key problem

Hi all,

i have problems with tables an foreign keys. i created the following
tables: (i did not copy all the command, only the important (in my point of view)

CREATE TABLE element (
id bigint NOT NULL,
site_id bigint,
type_id bigint NOT NULL,
name character varying(512),
description text,
active boolean NOT NULL
);

CREATE TABLE crmuser (
username character varying(32) NOT NULL,
firstname character varying(64),
lastname character varying(64)
)
INHERITS (element);

CREATE TABLE "comment" (
user_id bigint,
created timestamp without time zone,
content text,
element_id bigint NOT NULL
)
INHERITS (element);

CREATE INDEX idx_comment_id ON "comment" USING btree (id);

CREATE INDEX idx_comment_user_id ON "comment" USING btree (user_id);

CREATE INDEX idx_comment_element_id ON "comment" USING btree (element_id);

ALTER TABLE ONLY element
ADD CONSTRAINT element_pkey PRIMARY KEY (id);

ALTER TABLE ONLY crmuser
ADD CONSTRAINT crmuser_pkey PRIMARY KEY (id);

ALTER TABLE ONLY "comment"
ADD CONSTRAINT comment_pkey PRIMARY KEY (id);

ALTER TABLE ONLY "comment"
ADD CONSTRAINT "$3" FOREIGN KEY (user_id) REFERENCES crmuser(id);

ALTER TABLE ONLY "comment"
ADD CONSTRAINT "$4" FOREIGN KEY (element_id) REFERENCES element(id);

when i try to insert an comment with element_id = id of an user which is
visible when i call "select * from element", i get an foreign key
violation error: element_id=XY is not available in element.

i would like to reference to the element table, because i have some
tables which inherit from element and i would like to add comments to
these elements.

is this impossible or did i do a silly mistake? i did not find a
solution unsing google.

- Moritz

--
Wissen ist das einzige Gut, das sich vermehrt, wenn man es teilt.
--
http://www.lagerkochbuch.ch