The need for filtering of services results from the ever growing number of available web services that may be used to compose various business applications. Some of the available web services offer similar functionalities, thus the need to differentiate between them occurs. The semantic web services filtering process is therefore based not only on the ontological description of functional aspects of services (i.e. what a service does), but also on a description of nonfunctional ones (i.e. how it performs its functionality).