Google made its protocol buffers language publicly available. Our american pals have been using this data description language internally for a long time and because of its simplicity and thus ease (and speed) of processing has quite some advantages when compared to XML. If you only need a simple serialization data format to convey information and do not need complex processing techniques, then you might wanna have a look at protocol buffers. Protocol buffers provides simple models: lists and records while making the size of data necessary to encode information 3 to 10 times smaller than XML-based formats (dialects). Parsing is said to be 20 to 100 times quicker. Using the simple list and record structures, it is possible to generate classes in a target language such as python or java or any language of choice in order to write logic for those structures.
The language has now gone open source. So something similar to IDL but google guys say it is not as complicated. See google's announcement here and the page of the project on google code here, where you can among other things download the project.
Marwane El Kharbili
Source: JournalDuNet: http://www.journaldunet.com/developpeur/breve/international/29225/google-propose-une-alternative-a-xml.shtml