Thanks for all your feedback. Some of our XML files will require manual editing (pipelines and some materials) and we don't have many tools for that (although Volker is currently updating the material editor of the Horde Scene Editor). So binary files would make things incinvenient production-wise. But some time ago I was thinking about a custom XML-like format that could transparently be converted between the text and binary version. The basic idea is that the files have a simple node/attribute description table (also taken for validation) that is used to "compress" the files in the binary version. This would be cool but I still doubt that it is really required for now