Modelica is a general equation-based object-oriented language for continuous and discrete-event modeling of physical systems for the purpose of efficient simulation. The language unifies and generalizes previous objectoriented modeling languages. The Modelica modeling language and technology is being warmly received by the world community in modeling and simulation. It is bringing about a revolution in this area, based on its ease of use, visual design of models with combination of legolike predefined model building blocks, its ability to define model libraries with re-usable components and its support for modeling and simulation of complex applications involving parts from several application domains. In this paper we present the Modelica language with emphasis on its language features and one of the associated simulation environments. Simulation models can be developed in an integrated problem-solving environment by using a graphical editor for connection diagrams. Connections are established just by drawing lines between objects picked from a class library. The principles of object oriented physical systems modeling and the multi-domain capabilities of the language are presented in the paper by several examples.

This paper states the need for interactive teaching materials for programming languages within the area of modeling and simulation. We propose an interactive teaching material for the modeling language Modelica inspired by existing tutoring systems for Java and Scheme. The purpose of this new teaching material, called DrModelica, is to facilitate the learning of Modelica in a modeling and simulation environment. We have developed two versions of DrModelica, one that is based on Mathematica and another that is intended for the web. With the web version of DrModelica we hope for an increased usage of Modelica. 1. Background The concept of model, system and experiment are central in the area of modeling and simulation. “A model of a system is anything an “experiment ” can be applied to in order to answer questions about that system. ” [1] “A simulation is an experiment performed on a model. ” [1] Tools that are used for modeling and simulation are becoming a powerful aid in the product development process. Using advanced tools and languages to build a model of the product and then simulate its behavior before producing a physical prototype, minimizes the number of errors that can occur during fabrication. This minimization consequently leads to a decrease in the time needed to develop the final product. Furthermore, the earlier the errors are detected, the cheaper the corrections are. Not too long ago in the history of modeling and simulation technology, mathematical models were implemented by hand. The models were usually designed on paper using mathematical notation and the programs written manually in a high-level programming language, like C or Fortran, and stored in text files. Much manual work was needed, making not only maintenance of models expensive, but also the modification of models in order to adapt to new requirements [2]. 2. Modelica Modelica is a new language for hierarchical objectoriented physical modeling which is being developed