Collaborative modeling in graph based environments

This dissertation presents a conceptual approach and a corresponding system implementation to support collaborative modeling with graph based representations. Motivated by promising application potential in the field of education, the work is methodologically rooted in computer science, at the intersection of fields like metamodeling, software design, distributed systems, and visual languages in HCI contexts. The work presents the concepts of visual typed graphs and Reference Frames as formal notations for models and modeling languages usable in collaborative contexts. On this conceptual level, interoperability issues for shared heterogeneous models are discussed. Building upon existing libraries for communication support and graph representations, an architecture as a base for system implementations of the Reference Frame approach is presented. This architecture offers rule based syntax specification options and support for model synchronization. Furthermore, it contains a lightweight event based mechanism for model interpretation (which comprises model simulation functionality), and options for Reference Frame interoperability also on the implementation level. Cool Modes as one example system using the Reference Frame architecture is presented. This application manages multiple Reference Frames and supports collaboration relying on a „shared workspace“ metaphor. Through specific user interfaces for Reference Frames, the users are provided with an easy means to build heterogeneous models using primitives that externally definable and „pluggable“ modeling languages provide. Cool Modes as a tool which offers multiple work phases and several forms of partial synchronization (relying on language-specific synchronization contexts) is described. This thesis concludes with an evaluation of the Cool Modes system: several non-technical requirements which are not suitable for formal proofs (like, e. g., social interoperability) are evaluated on the base of interviews conducted with programmers who have used the application framework, and with teachers who have conducted lessons using the Cool Modes environment.