The idea was that we support `.cifx` files, which are not textual CIF files in the CIF ASCII syntax, but rather the EMF models serialized as XML (or rather XMI). I assumed this (still) worked, but it doesn't. Using `.cifx` as a file extension just means you still get a textual output file. The CIF type checker still configures this `cifx` file extension. But, the `cifx` file extension is not registered with EMF any more, it seems. Only the `cif` file extension is registered with EMF. Also, `CifWriter` always uses the CIF pretty printer, and `CifReader` always uses the CIF parser. Changes to be made: * Register the `cifx` file extension with EMF, to allow reading/writing such files. * Change the `CifWriter` to write XMI files when the file extension is `cifx`. * Change the `CifReader` to read XMI files when the file extension is `cifx`.