Core interceptor interfaces which form the basis for message processing chains in CXF. Interceptors are grouped into ordered lists called an interceptor chains. There is both an outbound and an inbound interceptor chain for both a CXF-based SOAP client, and a CXF-based web service. Additionally, in the case of SOAPFaults, a CXF web service will create a separate outbound error handling chain and the client an inbound one.