Web services based on PROLOG and XML

This paper describes how the deductive power of PROLOG can be made available across the Internet using standardized Web services technologies. This facilitates the use of PROLOG as a component of distributed information systems and in many new application scenarios. Some of those application scenarios are discussed and one is presented in greater detail. Since a lot of information available on the Internet is nowadays XML based and since Web services technologies use XML based encodings, it is both necessary and useful to be able to process XML documents in PROLOG itself. To make this possible, a new package for SWI-PROLOG called x2p is introduced, making available to PROLOG many of the XML processing facilities of the Libxm12 library, which is a very up-to-date and efficient implementation of most of the current XML related standards.