The concepts of [overdetermined](http://eom.springer.de/O/o070660.htm) and [underdetermined](http://eom.springer.de/u/u095150.htm) PDE systems are well known. However, all sources I have so far looked into appear to avoid giving any name to PDE systems which are *neither* overdetermined *nor* underdetermined. Is there any reasonably commonly used name for such PDE systems? If possible, please provide the references where the name from your answer is used.


**EDIT:** It was suggested by Igor Khavkine and Robert Bryant that one should consider *formally integrable* systems (which are neither over- nor underdetermined and have no nontrivial compatibility conditions). I like the idea but in my case this term would appear within the discussion of systems which are *completely integrable* (via the inverse scattering transform), and this might confuse the non-expert readers. Is there any sensible way out of this conundrum?


Thanks in advance!



A name for PDE systems which are neither under- nor overdetermined?
determined: Bryant et. al, Exterior Differential Systems, p. 189


