create table node (
    node_id integer not null unique primary key,
    type_nodetype integer not null references node,
    author_user integer not null references node,
    lastedit timestamp
);

create table user (
    user_id integer not null references node    
);

create table note (
    note_id integer not null unique primary key references node(node_id),
    doctext text not null default ''
);