This paper is presenting the design proposal of a simplified version of the Modelica language. Base Modelica is designed to serve as an intermediate representation enabling a clean separation of front-end and back-end matters when processing a Modelica model. Furthermore, is it intended as a basis to restructure the Modelica Language Specification considering two parts: the basic features and the advanced language constructs.

After discussing the motivation, solution approach, and risks, the paper is highlighting a selection of design choices that have been made for the current pre-release version of the language. Code examples are given to illustrate and highlight various aspects of the language. Open issues, conclusions, and an outlook finalize the paper.

By attracting more tool vendors and researchers to work with this intermediate representation the whole Modelica community is expected to benefit from new utilities to inspect, analyze, optimize and process equations-based models in general and Modelica models in particular.

Partitioned simulation or co-simulation allows simulating complex systems by breaking them up into smaller subsystems. The Functional Mock-Up Interface (FMI) enables co-simulation for models based on ODEs and DAEs, but typically not PDEs. However, only PDE-based models are able to accurately simulate physical aspects requiring spatial resolution, such as heat transfer or fluid-structure interaction.

We present a preCICE-FMI runner software to integrate FMUs with the open-source coupling library preCICE. preCICE couples PDE-based simulation programs, such as OpenFOAM or FEniCS, in a black-box fashion to achieve partitioned multi-physics simulations. The runner serves as an importer to execute any FMU and to steer the simulation. Additionally, it calls preCICE to communicate and coordinate with other programs. The software is written in Python and relies on the Python package FMPy. We showcase two example cases for the coupling of FMUs to ODE- and PDE-based models.

FMI is a standard for exchanging simulation models in a platform-agnostic way, also in form of black-box models. In the industrial context, it is common to exchange such black-box simulation models especially between partners. Using and running such models, though, is a security issue as there is no way to verify and validate the content of the models. This security issue must be addressed especially in the industrial context where security is considered high priority in general. Based on an exemplary model exchange, possible attacks are analyzed in this work. By using cryptography, three different approaches to pack the additional metadata are presented that aim at providing end-to-end integrity checks to a black-box simulation models. Together with administrative measures, this allows to define those FMUs to be trusted and executed. For sake of completeness, a prototype was implemented to help with the cryptographic processes and show the effectiveness of the provided solution.