XML schema/format for representing a generic file format?

Is there an existing XML schema that can be used to describe a generic file format? Something that would have tags that say things like "The file has a header that is x bytes long", "The first element of the header is a 4 byte unsigned integer that represents the length of the file", etc. ? I need a format of this sort and wanted to make sure there was not an existing standard one before I come up with one myself, since it seems like the kind of thing that might already be out there. Unfortunately, my Google searches have led me nowhere, but I don't know if that's because there's nothing out there or I just 开发者_JAVA技巧don't know the right search terms.

I would consider what has been done by x12.org for EDI. Their file formats are commerce oriented, but may cover what you have in mind.