I. Introduction
Web services are self-contained, modular, distributed, dynamic applications that can be described, published, located, or accessed over the network to create products, processes, and supply chains. Mashups are a new type of Web service that is composed of Web APIs. Mashups leverage content from different data sources to create new services. Hereafter, Mashups and Web APIs are also referred to as Web services in this work. Due to the advantages of Mashup technology, more and more developers and ordinary users tend to use Mashups to solve their business requirements. The great demand from users stimulates developer users to publish Web APIs on the Internet. Thus, a plentiful number of Web services are published on the Internet. Take the well-known ProgrammableWeb platform as an example, which hosts over 24,000 APIs and 8,000 Mashups. With such a huge number of Web services on the Web, how to manage them efficiently by means of web services classification according to their functionality is of great importance for further tasks, like service discovery or selection, service composition, and service recommendation [1]. However, there are two main challenging issues for accurate Web services classification. The first one is how to extract sufficient multi-dimensional features from the service repository since functional features of Web services are very limited by extracting from service descriptions. The second one is how to train an effective classification model with the extracted features since complex relationships may exist among different features.