Computing full disjunction using COJO

The Internet has provided users with access to wealth of information available on the Web, a considerable amount of which is semi-structured. In recent times, there has grown a need to access this information in an interpretable and meaningful way. One way to access this information is by transforming it into relations and integrating the relations to arrive at a universal relation thus ensuring simple and powerful searching of the underlying semi-structured data. Several operations exist for integrating these relations, like outer union, natural inner join, natural outer join etc., of which natural outer join has been found to be most effective in terms of achieving meaningful results i.e. full disjunction of the relations. Since natural outer join is non-associative, for more than two relations only some of the natural outer join ordering may lead to full disjunction. The Correct Outer Join Ordering (COJO) strategy proposed in this paper computes such natural outer join ordering of relations leading to full disjunction. It is further shown that the natural outer join ordering of relations produced by algorithm COJO compares well with the well-known algorithm SOJO on performance parameters.