Schematron using XPath 2.0 The attribute bc_mpo_bel:Instrument_Information/bc_mpo_bel:instrument_version must be equal to one of the following values 'BELA Flight Model', 'BELA Flight Spare'. The attribute bc_mpo_bel:Instrument_Information/bc_mpo_bel:instrument_version_id must be equal to one of the following values 'FM', 'FS'.