ASDL is also a common misspelling of ADSL.
Abstract-Type and Scheme-Definition Language (ASDL) is a computer language developed as part of ESPRIT project GRASPIN, as a basis for generating language-based editors and environments. It combines an object-oriented type system, syntax-directed translation schemes and a target-language interface.
References
Abstract-Type and Scheme-Definition Language Wikipedia(Text) CC BY-SA