To do what you want to do would require an enhancement to xml_iarchive and perhaps xml_oarchive as well. Doable, but to do it one would have to understand the implemenation of the library more than a casual user would want to. Robert Ramey "ari vol" <avf99avf@yahoo.com> wrote in message news:745938.47082.qm@web45315.mail.sp1.yahoo.com... The problem with this solution is that it is time consuming, to open file for a key, i would like to use the boost serializeation to improve time preformance. What is realy required is some mechanism, to identify an instance according to its key and only than read its data. Thus reading only the required instnace (accordig to its key) and not also the previous data at the file, someting like seek. I hoped that "XML boost" can supply someting like that, but could not find how.