This theory was developed by the Australian linguist Barry Blake.
[1] His theory was inspired by the approach of Italian linguist Guglielmo Cinque.
Many forms of Central German such as Colognian or Luxembourgish have a dative case but lack a genitive.
In Irish nouns, the nominative and accusative have fallen together, while the dative case has remained separate in some paradigms; Irish also has a genitive and vocative case.
Blake argues that it is "doubtful that the hierarchy can be extended much further", but does suggest that the most common cases not listed in the hierarchy are the comitative, purposive, allative, perlative and comparative.