title: implementation of two semantic query optimization techniques in db2 universal database. authors: k. bernhard schiefer , fred koo , t. y. cliff leung , linqi liu , jarek gryz , xiaoyan qian , qi cheng. venue: vldb. year: 1999.0
title: optimizing queries with universal quantification in object-oriented and object-relational databases jens clau &#223; en , alfons kemper , guido moerkotte , klaus peithner. authors: nan. venue: very large data bases. year: 1997.0