Drawings Do Not Equal Models

Published by on May 26, 2015 at 3:22 pm.

The True Definition of Model-Based Systems Engineering

Not-equal-symbolModel-Based Systems Engineering (MBSE) is the new buzzword. Everyone talks about “modeling” and “simulation,” but apparently many have conflated the concept of a model with a set of drawings or a specific drawing. MBSE originally meant the capturing of information that describes a system and then viewing that information in many different ways to enable understanding and articulation of detailed specifications or requirements for building a system.

The idea to push MBSE was to find a way to reduce the cost and time required to perform systems engineering, thus making it more likely to be performed properly. The cost and effect of not doing systems engineering have been well documented. So if MBSE is to be of value, it must reduce these costs and times sufficiently to make the cost of tools and training worthwhile. A tool that just produces drawings, even if it has a database which allows reuse, misses the point. With those tools, you have to create each drawing separately (say a SysML activity model and a sequence diagram). An underlying database may help you synchronize the information, but you still have to manipulate it in the diagram. A true model-based tool will draw the correct diagram automatically. This difference saves significant time in the creation, but even more in updating, validating, and making sure the diagram is accurate. Putting logic errors in the drawing means that those errors may not be discovered until much later in the lifecycle, where the cost of fixing design errors becomes very, very expensive.

Another difference between drawing-based vs. model-based tools comes in the capturing of a more complete set of information. Most model-based tools have more complete ontologies (bins of information and their relationships) than the typical drawing-based tool. Thus you can create a more complete specification using these kinds of tools. Innoslate® bases its ontology on the Lifecycle Modeling Language (LML), which was designed to capture the information needed across the entire product lifecycle, including operations and support. As such, Innoslate generates more complete specifications, standard operating procedures, and other critical documentation needed by the stakeholders, all at reduced costs in labor and tool price.

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