Hi List, I'm seing a little problem I can't understand with a small 27M thesaurus database. I created all indexes. When using the '!=' operator to compare two lists, I get a quick and wrong result: ------- *Case 1:* let $a := /thesaurus/entry/synonym/term let $b := /thesaurus/entry/term return $a[. = $b] ---> First result: "raccourcir" ------- and ------- *Case 2:* let $a := /thesaurus/entry/synonym/term let $b := /thesaurus/entry/term return $a[. != $b] ---> First result: "raccourcir" ------ while ------ *Case 3:* count(//entry[term='raccourcir']) --> result: 1 ------- But when I use the "not()" function as usual: ------ *Case 4:* let $a := /thesaurus/entry/synonym/term let $b := /thesaurus/entry/term return $a[not(.=$b)] ------- It dies out of memory. Is there something I did not see ? tx Xavier-Laurent Salvador