If, for some reason, you are coming upon this book without any previous knowledge of Modelica, there are probably a couple of questions you have. Let me attempt to address these questions in the hope that they will intrigue you and cause you to dig deeper.
Modelica is a high-level declarative language for describing mathematical behavior. It is typically applied to engineering systems and can be used to easily describe the behavior of different types of engineering components (e.g., springs, resistors, clutches, etc.). These components can then be combined into subsystems, systems or even architectures.
Modelica is compelling for several reasons. First and foremost, it is technically very capable. By using complex algorithms behind the scenes, Modelica compilers allow engineers to focus on high-level mathematical descriptions of component behavior and get high performance simulation capability in return without having to be deeply knowledgeable about complex topics like differential-algebraic equations, symbolic manipulation, numeric solvers, code generation, post-processing, etc..
The key to Modelica’s technical success is its support for a wide range of modeling formalisms that allow the description of both continuous and discrete behavior framed in the context of hybrid differential-algebraic equations. The language supports both causal (often used for control system design) and acausal (often used in creating schematic oriented physical designs) approaches within the same model.
Finally, another compelling aspect of Modelica is the fact that it was designed from the start as an open language. The specification is freely available and tool vendors are encouraged to support the import and export of Modelica (without being compelled to pay any royalty of any kind).
Modelica is really an ideal language for modeling the behavior of engineering systems in nearly any engineering domain. It seamlessly supports both physical design and control design in a single language. It is also multi-domain so it doesn’t impose any artificial boundaries that restrict its use to select engineering domains or systems. The result is that it provides a complete set of capabilities for building lumped system models of nearly any engineering system.