The ILLiad Patron Request Service is a web service installed on a site's local ILLiad web server that allows you to send requests to ILLiad without using the standard ILLiad web interface and pages. It also allows for retrieving a list of current requests to view in another web interface.
The ILLiad Patron Request Service is currently used only by sites using the OCLC Navigator project. It is NOT part of the standard ILLiad release.