read abt Conversions at 3: Object Publishing http://www.zope.org/Documentation/ZDG/ObjectPublishing.stx 3.2.6 ZPublisher http://www.dieter.handshake.de/pyprojects/zope/book/chap3.html FormVariableTypes http://www.zope.org/Members/Zen/howto/FormVariableTypes or chap 8 Advanced DTML of zope book