Q on associative binary operation

hi, Table shown is completed to define 'associative' binary operation * on S={a,b,c,d}. *|a|b|c|d --------- a|a|b|c|d --------- b|b|a|c|d --------- c|c|d|c|d --------- d|d|c|c|d The operation * is associative iff (a*b)*c=a*(b*c) for all a,b,c element of set S. So can (a*d)*d=a*(d*d)=d considered as associative over * for this case as per definition? Regards Sarath. __________________________________ Do you Yahoo!? Yahoo! SiteBuilder - Free, easy-to-use web site design software http://sitebuilder.yahoo.com