WHAT IS MODELING ABOUT?
George E.P. Box, said: “Essentially, all models are wrong, some models are useful.”
Modeling, in the broadest sense, is the cost-effective use of something in place of something else for some cognitive purpose. It allows us to use something that is simpler, safer or cheaper than “reality.” A model represents reality for some given purpose and is an abstraction of reality in the sense that it cannot represent all aspects of reality. This allows us to deal with the world in a simplified manner, avoiding the risk, complexity, danger and irreversibility of reality.
We first introduce some fundamental concepts and terms about models in general, and models for engineering in specific. Those include:
- Precise languages with formal syntax and semantics, including some with graphical notations
- Automation provided by computer-based tools which are enabled by precise languages
One key aspect of models and modeling is abstraction, which supports communication through different views with various levels of details. Details of importance can be emphasized while other details are not described. Most of us have been exposed to models for a long time, for example, a mobile of the solar system, as shown in Figure 1 shows the number of planets in our solar system; it might show the relative position of the planets, but it does not accurately show the planet’s size or distance from the sun. Different views provide alternative perspectives on the planets of the solar system and emphasize the relative size of the planets. To get an accurate perspective of a problem or solution often requires several views with some type of formal description of the relationship between the views. For example, the distance from the sun to each planet needs to be described using consistent units (e.g., miles, kilometers).
There are different levels of abstraction, which is where some differences between MBE vs. MBSE become apparent. First, MBE and MBSE are paradigms, because they are distinct sets of concepts or thought patterns that are applied to the subfields of engineering. This means there are many possible processes, methods, tools and languages that can be characterized as either MBE and/or MBSE. Second, the term MBE was first used back in 1980s, if not earlier. The term MBSE emerged in the early 2000s to address the challenge of increasing system complexity. Evolving technologies for MBSE enabled engineers to move away from document-based systems engineering to model-based systems engineering.
MBE is a name given to various types of models, such as mechanical, electrical and software models as discussed in Section 3. MBSE models as reflected by a System Model that characterizes the relationships and interface between one or more subsystem models that may be combinations of mechanical, electrical and software. A case study provided in Section 2 helps explain the different uses for MBE vs. MBSE.