We already have envVarRef support, e.g.
<string>
<envVarRef>MODELS_HOME</envVarRef>/master.ddinf
</string>
which allows multiple substitutions anywhere in the string. It is currently
restricted to the System properties but we could let a -D specified
properties file override or augment that.
Personally I'd like to see a simpler syntax although it would require more
code changes. e.g.
<string prop="MODELS_HOME">
MODELS_HOME/master.ddinf
</string>
Avoids the need for a new element and documenting what characters terminate
the variable, although it is a familiar syntax, e.g.
<stringWithVariables>
$MODELS_HOME/master.ddinf
</stringWithVariables>
~Burn
