I have created an IDML package that is very basic. It has a couple of spreads, each with a single page and some guides on the page. Schema validation against the package schema passes. However, when I open the file in InDesign it tells me "Cannot open then file 'foo.idml'. Adobe InDesign may not support the file format, a plug-in that suports the file format may be missing, or the file may be open in another application."
It is not open in another application and helloworld-2.idml opens fine even through it fails validation on several counts.
I suspect there is something very minor "wrong" with my IDML file. However, given that the schema is not catching it; is there a way to determine why InDesign chokes on it? I don't see any log file, nor is there anything in the Windows event log. Does anyone know how to determine what it is about the file that InDesign can't handle?
Your IDML file is zipped, right? If you have raw XML, then you should probably name it .idms or something...InDesign expects a .IDML file to be a zipped archive.
Beyond the schema validation? Err, well, take an existing minimal working IDML file and start moving parts of your file into it until it breaks, I'm afraid. It's a bit of a pain but not too much work.