In web-service fundamental, I have heard about "SOAP" and "KSOAP."
SOAP - SOAP is an XML vocabulary used to describe messaging and remote procedure calls between distributed components.Any modern language that works with the Internet is likely to support both XML and HTTP.
KSOAP - KSOAP is a SOAP API based on kXML,where kXML is a lightweight Java-based XML parser designed to run on limited, embedded systems such as personal mobile devices. It is a pull parser which means it reads a little bit of the document at once
So, KSOAP was specially was designed or developed to deal with small embedded device like mobile devices.
SOAP - Most enterprise-level SOAP toolkits often rely on the use of a Web Services Description Language (WSDL) generated proxy object to make function calls. This is useful if a service has a published description and when the toolkit requires the instantiation of several different client and transport objects.
KSOAP - While kSOAP doesn't support WSDL, it does make calling a service relatively painless. Only two objects are required: the SOAPObject and Http-Transport.
CONCLUSION - SOAP can be a very complex realm to explore, especially the XML mechanisms used to transfer data between disparate systems, languages, and toolkits. The wireless world requires tools of small stature and great power. Luckily when it comes to SOAP, the kSOAP toolkit provides not only small size and great functionality, but also relative simplicity and ease of use for the developer. Using kSOAP, a developer can develop complex SOAP Web services clients in a remarkably short time.