1. Introduction
As a consequence of the popularity and advancement of related
web and information technology, massive amounts of data are produced
in our daily life. Large volumes of information, petabytes of
data, are recorded every day. Clearly, the era of big data has arrived
(Mayer-Schonberger and Cukier, 2014). In addition to the data size
(i.e. volume), big data has other characteristics, such as variety and
velocity. The former means that big data can be composed of a
wide variety of structured, semi-structured, and unstructured data
whereas the latter refers to the requirement of real-time processing
and analysis (Fernandez et al., 2014). As a result, big data analytics
by machine learning and data mining techniques has become