For each ASN1 types SET and SEQUENCE a record is generated in the .hrl file with the same name as the corresponding type. A decoded value is also returned as a record with the appropriate name. An internally defined type as the type in component 'a' in the following example will result in a record with name 'Seq_a': Seq ::= SEQUENCE{ a SEQUENCE{ b INTEGER } } For each further internally defined type in a SET/SEQUENCE a '_componentname' is added. If an internally defined type is an CHOICE alternative the record name will get the alternative name as a unique part of the name. Seq ::= SEQUENCE{ a CHOICE{ b SEQUENCE { c INTEGER } } } This will produece a record 'Seq_a_b'. If an component is a SEQUENCE OF a SEQUENCE as in: Seq ::= SEQUENCE { a SEQUENCE OF SEQUENCE { b } c SET OF SEQUENCE { d } } There will be a record 'Seq_a_SEQOF' and 'Seq_c_SETOF' A parameterized type should be considered as an internally defined type. Each time a such type is referenced an instance of it is defined. Thus in the following example a record 'Seq_b' is generated in .hrl and used in .erl by decode. Seq ::= SEQUENCE { b PType{INTEGER} } PType{T} ::= SEQUENCE{ id T }