Abstract. Sophisticated uncertainty representation and reasoning are necessary for the alignment and integration of Web data from different sources. For this purpose the extension of the Description Logics using fuzzy set theory has been proposed, resulting to fuzzy Description Logics (DLs). However, despite the fact that since the initial proposal a lot of work has been done in the area, the practicability of very expressive fuzzy DLs still remains open, due to the absence of practically scalable systems. This paper presents optimization techniques that can improve the performance of fuzzy-DL systems β reasoning.