A specific aspect of interoperability within large scientific facilities is the management of different data formats associated with different fields. NeXus, HDF5 and CIF are scientific data formats that overlap in some areas (e.g. in the capture and management of X-ray diffraction images), and there is considerable benefit to be gained by harmonising their content and working towards maximum interoperability. Format conversion at the syntactic level can be a straightforward process, but truly interoperable software applications require functional mappings between different representation standards. An initial approach to this is being attempted by constructing a DDL2 dictionary, acting as a concordance between the existing NeXus and imgCIF formats. Full interconvertibility between NeXus and imgCIF relies on methods evaluation, and may be possible using the new dictionary definition language DDLm and an evaluation engine (such as dREL).