## 2 Related Work and State-Of-The-Art Technologies
### Related Work
They offer no possibility for the integration of many different kinds of models in order to build a more universal co-simulation platform for simulating realistic multi-domain energy system scenarios. An implementation of a more flexible cyber-physical energy system co-simulation framework is the tool Mosaik that has been developed at the Oldenburg Institute for Information Technology [16]. It provides APIs to integrate existing simulation models and simulators into Mosaik and then combines them to build smart grid scenarios [16; 17]. However, a specific implementation of the APIs by the users (e.g., writing glue code) is necessary. Moreover, as presented in [18], Mosaik can only provide the possibility to connect models and manage them in a coordinated simulation but has no support for e.g., integrating other auxiliary tools for data pre-processing or data forecasting to set up more advanced computational scientific workflows. Furthermore, as a conclusion of [19], Mosaik is suitable for entry-level, prototypical co-simulation but not for complex and extensive studies. Besides, Mosaik has no easy-to-use web user interface but a desktop user interface [20], which provides users only with a view of simulation results but no graphs of data routing, transformation and system mediation logic [5]. Ref. [21] describes an open-source \"framework for network co-simulation\" (FNCS) for power system transmission and distribution dynamics co-simulation. FNCS provides libraries for supporting C, Java, Matlab, Python and FORTRAN interfaces for flexible simulator integration. Besides, FNCS has no limit on the number of participating simulators and great scalability. However, users need to extend the simulators to use the interfaces for boundary buses that need to communicate with others through FNCS. No easy user interface is provided by FNCS for users to integrate their simulators and then build co-simulation scenarios easily. Ref. [22] presents the design rationale for the hierarchical engine for large-scale Infrastructure co-simulation (HELICS), a new open-source, cyber-physical-energy co-simulation framework for electric power systems. By using HELICS, large-scale co-simulations with off-the-shelf power-system, communication, market and end-use tools can be built. However, users have to implement programming interfaces to combine their simulators with HELICS. Moreover, by using the Matlab API, HELICS can only interact with Matlab models running in Matlab environments providing a commercial Matlab license. Contrarily, the framework presented in this article can launch standalone Matlab executables in containers without the need for a Matlab license by using exported binaries and distribute them on the scalable computing cluster easily, flexibly and efficiently. One main result of the literature study was that--at least to our knowledge--there is currently no existing solution that fulfils all the mentioned requirements for a more generic framework for setting up and managing complex computational scientific workflows. Apache NiFi, for example, implements some very good base functionalities needed for such an environment, but lacks some features for the more advanced coordination of workflow steps which is needed to set up more complex workflows. However, the literature study also shows that such an environment could be created by combining the right technologies and integrating them into a comprehensive framework.