Classification and mapping of layout algorithms for usage in graph-like modeling languages

Graph-lik>modeling languages (GLML) are important modeling artifacts for software tools that are used in the environment of software and systems engineering, digital twins, and domain-specific modeling. Just as with textual languages, the concrete syntax is the representation of the language elements intended for humans and thus has a decisive influence on the comprehensibility and usability of the language. The concrete syntax of GLML is often defined less precisely or in less detail when designing metamodels. While metamodels can be designed independently or even without concrete syntax, the latter is required for the actual usage of a graphical language. The layout and the interaction support for editing the language elements are commonly delegated to tool development. However, the development of modeling tools focuses on functionality such as model transformation and model execution, disregarding usability and handling. Low user acceptance then leads to niche applications and a limited number of users. The main reason for the lack of support for laying out and editing the language elements are complex integration challenges mainly concerning the development or adaptation of suitable layout procedures for GLML. Some frameworks offer a remedy by providing layout procedures for GLML. However, GLML differ from each other concerning their concrete syntax. Even minor differences in the concrete syntax of two languages can make the desirransferable or only transferable through complex adaptations. Formal methods for matching the concrete syntax of a GLML with existing layout procedures as early as during the development of the language are missing. In this paper, we present a classification scheme for layout procedures for GLML. The classification scheme is based on a classification scheme we developed for the concrete syntax of GLML, and it contains significant features. We define a mapping procedure between the two classifiers. As a result, the mapping decides whether a layout procedure can be used for a GLML. Both the classification scheme and the process of mapping are demonstrated in a real-world example of a technical graphical domain-specific modeling language. The presented approach supports the design of GLML and the tool development for GLML. It can be an important step towards automated tool development.