A ServerProxy instance has a method corresponding to each remote procedure call accepted by the XML-RPC server. Calling the method performs an RPC, dispatched by both name and argument signature (e.g. the same method name can be overloaded with multiple argument signatures). The RPC finishes by returning a value, which may be either returned data in a conformant type or a Fault or ProtocolError object indicating an error.
Servers that support the XML introspection API support some common methods grouped under the reserved system member:
Because multiple signatures (ie. overloading) is permitted, this method returns a list of signatures rather than a singleton.
Signatures themselves are restricted to the top level parameters expected by a method. For instance if a method expects one array of structs as a parameter, and it returns a string, its signature is simply "string, array". If it expects three integers and returns a string, its signature is "string, int, int, int".
If no signature is defined for the method, a non-array value is returned. In Python this means that the type of the returned value will be something other that list.
Introspection methods are currently supported by servers written in PHP, C and Microsoft .NET. Partial introspection support is included in recent updates to UserLand Frontier. Introspection support for Perl, Python and Java is available at the XML-RPC Hacks page.
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