Closure table triggers

add.sql

-- NOTE: Organizations have id and parentOrgId columns
-- OrgClosure has parentId, childId, depth columns

CREATE OR REPLACE TRIGGER Org_Add_Trigger
    AFTER INSERT ON Organization
    REFERENCING NEW AS NEW
    FOR EACH ROW
BEGIN
    -- must insert in this order...
    insert into OrgClosure (parentId, childId, depth)
    VALUES (NEW.id, NEW.id, 0);

    insert into OrgClosure (parentId, childId, depth)
    select p.parentId, c.childId, p.depth+c.depth+1 as depth
    from OrgClosure p, OrgClosure c
    where p.childId=NEW.parentOrgId and c.parentId=NEW.id;
END

delete.sql

CREATE OR REPLACE TRIGGER Org_Delete_Trigger
    AFTER DELETE ON Organization
    REFERENCING OLD AS OLD
    FOR EACH ROW
BEGIN
--     delete link
--     from OrgClosure p, OrgClosure link, OrgClosure c
--     where p.parentId = link.parentId and c.childId = link.childId
--     and p.childId = OLD.parentOrgId and c.parentId = OLD.id;

    delete from OrgClosure as O where exists (
        SELECT 1
        FROM OrgClosure p, OrgClosure c
        WHERE p.parentId = O.parentId AND c.childId = O.childId
              AND p.childId = OLD.parentOrgId
              AND c.parentId = OLD.id
    );
END

If you don't mind, I didn't get the delete trigger?
can you explain?