This chapter presents the design and development of WebDisC, a knowledge-based web information system for the fusion of classifiers induced at geographically distributed databases. The main features of our system are: (i) a declarative rule language for classifier selection that allows the combination of syntactically heterogeneous distributed classifiers; (ii) a variety of standard methods for fusing the output of distributed classifiers; (iii) a new approach for clustering classifiers in order to deal with the semantic heterogeneity of distributed classifiers, detect their interesting similarities and differences, and enhance their fusion; and (iv) an architecture based on the Web services paradigm that utilizes the open and scalable standards of XML and SOAP.