Out-maps are used in encoders to map an internal format to an external format.

internal IFormat1 {
    int f1;
    ascii f2;
};
external EFormat1 {
    ascii f1 : static_size(2), terminated_by(" ");
    ascii f2 : static_size(10), terminated_by(" ");
};
out_map OutMap : internal(IFormat1), external(EFormat1) {
    automatic;
};

As for in-maps, specially named options can also be supplied in the out_map depending on the type of the external format. The type specific options are:

An internal field can be defined as optional, enabling to encode the corresponding external field as not present. Internal fields with value null may still be considered present and are encoded as, for instance, an empty string. To override this, use the APL command udrUnsetPresent prior to encoding.

Consider the following example, where an optional field within an incoming ASN.1 record will be encoded (the definition of myInt varies).

asn_block { 
     main_udr ::= SEQUENCE { 
       fieldA [APPLICATION 5] INTEGER OPTIONAL 
     }; 
 }; 
 in_map inM :   external( main_udr ), 
               internal( myInt ) { 
                   automatic;
}; 
 out_map outM : internal( myInt ), 
                external( main_udr ) { 
                  automatic; 
 }; 
 decoder myDEC : in_map( inM ); 
 encoder myENC : out_map( outM );

internal myInt { 
      int fieldA : optional; 
 };

internal myInt { 
      int fieldA ; 
 };

internal myInt { 
 };