Quoting from Cisco Press Documents
"On point-to-point subinterfaces, you do not need to use the frame-relay map command to perform static address mapping, because it is always assumed that the end point of the point-to-point connection automatically resides on the same subnet as the start point. It is also not required to enable or disable Inverse ARP, because there is only a single remote destination on a point-to-point PVC and discovery is not necessary."
Link Reference
http://www.ciscopress.com/articles/article.asp?p=170741&seqNum=6&rl=1