For unresolvable packages, the edition requirements are merged in this structure and returned. If either 'greater' or 'less' are UNSPEC, there's no requirement in this direction. If both are UNSPEC, any edition will satisfy the requirements. Otherwise, a satisfying edition must be greater than 'greater' and less than 'less'. The {le,gr}_incl fields are true if the ranges are meant inclusive at the resp. border. 'impossible' is true if greater > less, i.e. there are contradicting requirements.