Definition Alias 
The aliases of operations on definitions whose return type is non-primitive are called definitions aliases.
Note
The eight primitive return types supported by the Java programming language are:
byte
short
int
long
float
double
boolean
char
End of the note.
Example
Address custAddress = null is a definition alias.
The Address object has operations like getCity(), getCountry().
Definition aliases of custAddress are:
custAddress.getCity()
custAddress.getCountry()
End of the example.
You can create a definition alias in the Project Resources and at the ruleset level.