I am developing a cross-platform application (for Windows, Mac etc.) and for 32-bit and 64-bit machines. I have lots of XML files which I need to validate against their
Obviously you need a cross-platform validator.
Maybe Libxml2 (http://xmlsoft.org/) is an option, as it can be used from many programming languages on many platforms.
A open source Pascal wrapper for Libxml2 is avalaible on http://sourceforge.net/projects/libxml2-pas/