note paulbort I know that it really doesn't address your topic, but I think the reason that you're running into the problem is that it's the wrong approach. An impressive (ab)use of regular expressions, though.<BR><BR> What I've seen of predicate systems leads me to a database approach rather than regular expressions. Given the right data structure, you need to write two parsers: one to convert $facts into rows in tables, and one to convert your queries into SQL. With the right data structure, this is straightforward. <BR><BR> Most of this can be done with three tables: One to contain people, things and attributes (Merlyn, Ovid, Kudra, books, gold, valuable), one to contain verbs ( owns, is ), and one to contain tuples of person/thing/attribute, verb, person/thing/attribute. This leads to something like: <CODE> SELECT actor FROM relations WHERE verb = 'owns' AND acted_on IN ( SELECT actor FROM relations WHERE verb = 'is' AND acted_on = 'valuable' ); </CODE> This query, with proper data, can answer the question of 'who owns something valuable' in a very reasonable amount of time. You still do code generation, but now it's SQL instead of RE. <BR><BR> HTH, <BR> Paul <div class="pmsig"><div class="pmsig-6562"> <br>--<br>Spring: Forces, Coiled Again! </div></div> 318350 318350