I. Introduction
Automatic topic identification is one of Text Mining areas, in which the task consists of recognizing the subject in which the text is written and talking about. In fact, topic identification is an important field and a primary task before tackling other Text Mining areas. For instance, in authorship attribution field it is important to know the topic in advance, because the author style changes from topic to another [1]. We can also find the topic identification in the civil security, in which automatic topic identification is used in analyzing emails and on-line conversations in order to predict manifestations and terrorist plots.