Throughout the history of phonology, there have been numerous attempts to explain the phenomenon of vowel fronting in German. Even OT is left with a number of problems when tackling German vowel fronting - because the process seems to originate from around the interface of phonology and morphology; because the phenomenon only seems to behave in more or less generalizable patterns; and because there is a lot of inter-speaker and intraspeaker variation.
This paper will start out by describing umlauting and umlaut-triggering conditions in some detail. The description will be followed by a brief overview of the most dominant ideas that had been brought forward in pre-OT literature, and the paper will close with a suggestion of a possible constraint-ranking responsible for umlauting, not forgetting the problems that remain even in an OT-based account.