ABSOLUTE vs RELATIVE network mapping reference

What is the best way in Framemaker to reference a mapped network drive, to open an externally linked .pdf?

ABSOLUTE network mapped drive: the following WORKS great.

message URL file://///xxxx/yyyy/images/TDTD_CS_Rev_working.pdf

RELATIVE network mapping: What is the best way to reference RELATIVE, and open a external .pdf file?

message URL file ?????

Your comments are appreciated.