If you use Sharepoint Designer to build workflows, sometimes you will feel the need of some extra actions in the designer (see below).Well Microsoft has provided with a class to do that, this class is call it DependencyProperty. MSDN defines the DependencyProperty like this: Represents a property that can be set through methods such as, styling, data binding, animation, and inheritance.
The browser sends a DAV packet to IIS asking to perform a document check in. PKMDASL.DLL, an ISAPI DLL, parses the packet and sees that it has the proprietary INVOKE command. Because of the existence of this command, the packet is passed off to msdmserv.exe, who in turn processes the packet and uses EXOLEDB to access the WSS, perform the operation and send the results back to the user in the form of XML