The Xairo API is the common low level entry point to the Xairo server. It is used by the various Xaira clients to accept queries and return solutions; it is also used by the SOAP server, which in turn exposes a higher level interface suitable to transfer of data by HTTP. Many users will not need to use the low level API and will use a client to solve queries. This documentation is for those wishing to use the C++ API. Some general programming considerations are discussed here and these should be consulted before the detailed API document pages.
There is also a Java API with Javadoc documentation almost identical to this in docs/api/java. The SOAP web service API is formally defined by the file Xaira.wsdl and informally in the docs/api/webserver directory.