  In this paper, a novel hierarchical Persian stemming approach based on the
Part-Of-Speech of the word in a sentence is presented. The implemented stemmer
includes hash tables and several deterministic finite automata in its different
levels of hierarchy for removing the prefixes and suffixes of the words. We had
two intentions in using hash tables in our method. The first one is that the
DFA don't support some special words, so hash table can partly solve the
addressed problem. the second goal is to speed up the implemented stemmer with
omitting the time that deterministic finite automata need. Because of the
hierarchical organization, this method is fast and flexible enough. Our
experiments on test sets from Hamshahri collection and security news (istna.ir)
show that our method has the average accuracy of 95.37% which is even improved
in using the method on a test set with common topics.
