## 2 Materials and Methods
### Simulation Planning  
Co-simulation scenarios typically have to be developed in cooperation of experts from different domains and a simulation expert. This cooperation poses potential challenges, because experts from different domains may have problems in understanding each other correctly due to differing terminology and backgrounds. Therefore, the presented co-simulation environment is extended by a process for integration of domain knowledge and structuring of the test scenarios. In this simulation planning process, it has to be defined what the objectives of the simulation are, what kind of objects should be considered, which simulation models are available and used, and which data flows are needed. Additionally, it should be possible to enrich the simulation objective definition with external domain knowledge and definitions of terms (see left-hand side of Figure 3). An approach for modeling these simulation objectives has been developed in form of a process to assist the planning of co-simulation scenarios for the investigation of energy scenarios [22]. It consists of a sustainability evaluation process (SEP) in combination with an information model as described by [PERSON] et al. [23]. In the SEP, the specific use case of co-simulation for the evaluation of possible future states of the energy system is addressed. As a first step, future scenarios are developed. Then these future scenarios are used to parameterize co-simulation setups. The last step of the SEP is the evaluation of sustainability of the simulation results and future scenario descriptions based on multi-criteria decision making. The information model supports the SEP and allows to model parameters, dependencies, and data flows of the simulation and evaluation [23]. As the process aims to allow the cooperation in an interdisciplinary project team, the focus lies on usability for a diverse group of domain experts. Thus, the modeling takes place in a mind map tree structure and a plug-in has been implemented to transform the content to a resource description framework (RDF) file for further automated processing. The modeling can start with the first rough planning of the objectives of a simulation in a brainstorming in the interdisciplinary project team. As the planning progresses, the structure of the system model has to be refined to comply to the structure of the information model. This allows the transformation of the output into further usable data formats. This high-level scenario description in the information model is the basis for the development of executable simulation scenarios. Especially for large-scale scenarios with simulation models from many different domains, the development of these scenarios is complex and the experts may need assistance. Additionally, a simulation scenario should be validated regarding its completeness, coherence, and correctness. Therefore, semantic web technologies are used to structure the available information and allow the seamless integration of external domain knowledge. The information model structure is described by a base ontology [24]. Thus, the content of the information model is available for querying with the SPARQL query language. For the development of executable simulation scenarios, the content of the information model has to be combined with information about the available simulation models. For this, a standardized interface description of the simulation models is needed. FMI can offer technical specification of the interface [4], but additional information about the simulation models is required. To collect this information, a questionnaire has been developed which allows users to describe the characteristics of a simulation model. For example, the used mosaik interface technology, temporal and spatial resolution, or the modeled domains are described.