The Simple Object Access Protocol (SOAP) is a W3C (World Wide Web
Consortium) recommendation that essentially allows for Remote
Procedure Call (RPC) functionality over HTTP, via XML. (This is a
simplification of the 120-page SOAP spec, but it suits our
purposes). SOAP web services provides a systematic, defined way of
communicating function requests and responses over a network
transport.
SOAP interfaces are described by another W3C recommendation, WSDL
documents - Web Services Definition Language. WSDL documents are the
prototypes for SOAP functions. They define what parameters are
expected to the functions, what formats are/aren't allowed, what will
be returned, etc. Given the WSDL of a SOAP web service, programs can
generate the client code that interacts with the services (as is
demonstrated in the C# example project later).
Specifically for the Search Appliance, the SOAP interface provides,
when using a language that has a SOAP API, a way to invoke a search
and on
the Search Appliance and insert data as if it were a local function call.