The aim of this paper is the study of methods for assembly representation supporting the level of automation (LoA) decision .process. Based on a literature review on the topic of LoA deciding, a need for involving the assembly sequence in the decision was identified. The representation methods used in both assembly modeling and planning and other more generic approaches in the literature were studied and evaluated. The evaluation has been based on a requirements definition describing how the representation should support the decision about automation. Identified gaps in requirement satisfaction from the existing approaches led to the definition of the Assembly Sequence Modeling Language (ASML), a new modeling language that combines principles from and improvements on the studied methods and a standard vocabulary of assembly actions. The modeling language was demonstrated in an assembly example and was successfully evaluated with regard to the defined requirements. Thus, this new modeling approach, ASML, is offered as an innovative and intuitive support in the decision making process for selecting automation levels in Assembly.