XML-RPC is the remote procedure call protocol using XML for transferring small amounts of data back and forth using XML as the dta encoding. XML-RPC preceded Web Services and WSDLs and all of the standards committees, and it Just Works. For a view of what blogging aggregators and directories use for updates, check out Robin Good’s article “Increase Visibility in Blog and RSS Directories: XML-RPC Pings.” Realize if you are using one of the commercial blogging tools like Blogger or Radio, it is already performing the XML-RPCs in the background.