Multi-Level Conceptual Modeling: From A Formal Theory To A Well-Founded Language

Subject domains are often conceptualized with entities stratified into a rigid two-level structure: a level of classes and a level of individuals which instantiate these classes. Multi-level modeling extends the conventional two-level classification scheme by admitting classes that are also instances of other classes, a feature which is key in a number of subject domains. Despite the advances in multi-level modeling in the last decade, a number of requirements arising from representation needs in subject domains have not yet been addressed in current modeling approaches. In this paper, we tackle this issue by proposing an expressive multi-level conceptual modeling language (dubbed ML2). We follow a principled approach in the design of ML2, constructing its abstract syntax as to reflect a formal theory for multi-level modeling (termed MLT*). We show that ML2 enables the expression of a number of multi-level modeling scenarios that cannot be currently expressed in the existing multi-level modeling languages. A textual syntax for ML2 is provided with an implementation in Xtext.