Structuring large models with MONO: Notations, templates, and case studies

Abstract Context: With increasing size, modeling projects have a growing need for an internal structure, much like the directory structure coding projects use to store source code and other resources. An ill-fitting model structure can lead to increased effort, reduced quality, and decreased benefit derived from modeling. Examples for useful model structures and guidelines on how to create them are scarce, at best. Goal: We aspire to improve the practice of model structuring by providing templates and best practices based on practical experience. We want to foster documenting and sharing model structures by providing a visual notation to define such structures. Method: We analyze two very different modeling projects, one from industry and one from academia. By representing extremely different settings in terms of tooling, language, audience, and mindset, they represent a large portion of the space of modeling. We define a notation that allows to capture the outlines of both models, thus arguing for its high generality and expressiveness. Results: We develop the Model Outline NOtation (MONO) to describe generic model structures. We extract proven and effective model structuring templates and practices from two case studies. Conclusions: Providing an adequate structure to models is important, but little guidance exists currently. Based on two case studies, we aspire to fill this gap, providing both templates and a notation to document and share more model outlines.