In the IE languages the term "case" is more or less clear. There is a relatively small number of cases that are used with or without prepositions. Moreover, the case endigs have different forms according to paradigms and not to the fuctionality (eg. -a is gen.sg. of "muž", but also nom.pl. of "víno" in Slovak).
In the agglutinative languages like Hungarian, Turkish ... there are no prepositions, but a relatively high number (about 20-28 in Hungarian) of "endings" (or better morphemes attached to the noun, adjective...). A particular "ending" has always the same meaning/function (regardles of paradigms). Besides of these "endings", there is a plenty of postpositions that are written (and pronounced) separately from the preceding noun, otherwise they behave similarly as those "endings".
My question: is it linguistically correct to speak about cases in this kind of languages? If yes, then how many cases are there in Hungarian: 28 (according to the "endings") or only a subset of those 28 or also constructions with postpositions are to be consedered separate cases? In other words, what is the criterion for defining a "construction" as grammatical case?
Thanks in advance for your opinions!