Along with using FrontPage RPC Web methods, SharePoint Designer relies on a number of Web methods and functions exposed by SharePoint ASP.NET-based Web Services for the remote authoring of SharePoint sites. SharePoint Designer uses Simple Object Access Protocol (SOAP) to communicate with SharePoint Web Services for performing basic operations on SharePoint sites, including opening Web pages, rendering SharePoint content in the Design view, and implementing advanced features, such as Data Forms and Web Parts.
To be able to understand the background processes involved when working with SharePoint sites in SharePoint Designer, it's important to have some basic understanding of SOAP and ASP.NET Web Services. In this section, I discuss Web Services and SOAP as a communication protocol to converse with Web Services.
To put it in simple terms, SOAP allows a client program to remotely execute a method exposed by a Web Service being hosted on a Web server. Unlike the FrontPage RPC methods discussed earlier, the syntax of SOAP-based communication is mostly driven by XML-based messages. These XML messages are sent in the body of the HTTP request to the Web Service on the Web server. The Web Service processes the request based on the information in the HTTP request and formulates an HTML/XML response for use by the client.
Web Services are programs with an .asmx file extension that, ...