Is there any standards to follow while defining portability type in EPAP

while defining portability type in EPAP any standards need to follow, right now we are using as follows.

0   not known to be ported (used for block of ranges)

1  own number ported out (used for ported out case)

2  foreign ported to foreign (foreign network to foreign network porting case)

i want use portability type some number (may be 3) for specifically for port in cases, is this possible to define the same.

or already standards are present to use (some number) for port in case.

Please clarify on the standards.