MBSE Tool Reviews FAQ: Why use a MBSE modeling tool?

Model-Based Systems Engineering (MBSE) is a Systems Engineering paradigm that emphasizes the application of rigorous visual modeling principles and best practices to Systems Engineering activities throughout the System Development Life Cycle (SDLC). These Systems Engineering activities include, but are not limited to: requirements analysis, validation and verification; functional analysis and allocations; performance analysis and trade studies; and system architecture specification.

Usage Note: The term Model-Based Systems Engineering (MBSE) is especially popular among Systems Engineers who advocate the use of the Systems Modeling Language (SysML) as a standard visual architecture modeling language for Systems Engineering applications, and who want to distinguish their approach from Model-Driven Development and its variants, which tend to be software centric.

If you are a Systems Engineer and want to improve the precision and efficiency of your communications with fellow Systems Engineers and other system and business stakeholders (e.g., Clients, Software Engineers), then you should consider using a visual modeling language standard as a lingua franca (common language). The most popular choice for MBSE applications is the SysML dialect of UML 2, which extends the UML standard for software-intensive applications so that it can be applied to Systems Engineering applications.

Why apply MBSE technologies to your project?

Here's a list of reasons why Systems Engineers may want to use a Model-Based Systems Engineering approach with a common modeling language such as SysML for their work:

• Facilitate communication among various stakeholders across the System Development Life Cycle
• Capture and manage corporate Intellectual Property related to system architectures, designs, and processes
• Compare and contrast “As Is” and “To Be” solutions
• Provide scalable structure for problem solving
• Furnish rich abstractions to manage size and complexity
• Explore multiple solutions or ideas concurrently with minimal risk
• Detect errors and omissions early in System Development Life Cycle
  

For more information about MBSE technologies and their practical applications, check out the MBSE Works web.

The Systems Modeling Language (SysML) is a general-purpose architecture modeling language for specifying Systems Engineering applications.

• SysML supports the specification, analysis, design, verification, and validation of a broad range of systems and systems-of-systems. These systems may include hardware, software, information, processes, personnel, and facilities.
• SysML is a dialect of UML 2, and is defined as a UML 2 Profile (Profile = UML customization that uses Stereotypes, Tagged Values, and Constraints).
• SysML is an enabling technology for Model-Based Systems Engineering (MBSE).

SysML Origins: The SysML was original developed by the SysML Partners' open-source specification project, which was initiated in 2003 in response to OMG's "UML for Systems Engineering" Request for Proposals (RFP). The SysML contains nine diagram types, seven of which it shares with its UML 2 parent language, along with one tabular notation (Allocation tables). These seven shared diagrams are: Use Case, Block (nee Class in UML), Internal Block (nee Composite Structure in UML), Activity, Sequence, and State Machine. The two new diagrams that SysML contributes are Requirement (derived from Class diagrams) and Parametric (derived from Composite Structure diagram).

Why use SysML?: If you are a Systems Engineer and want to improve the precision and efficacy of your communcations with fellow Systems Engineers and other system and business stakeholders, then SysML is an excellent choice for a lingua franca (If, on the other hand, you are a Software Developer or a Business Analyst who wants to improve communications with your peer and other system stakeholders, then UML or BPMN may be a better choice). Here is a list of reasons that SysML Engineers may want to use SysML and a Model-Based Systems Engineering approach for their work:

• Facilitate communication among various stakeholders across the System Development Life Cycle;
• Capture and manage corporate Intellectual Property related to system architectures, designs, and processes;
• Compare and contrast "As Is" and "To Be" solutions;
• Provide scalable structure for problem solving;
• Furnish rich abstractions to manage size and complexity;
• Explore multiple solutions or ideas concurrently with minimal risk;
• Detect errors and omissions early in the System Development Life Cycle

Specification Availability: The SysML specification is publicly available for download, and includes an open-source license for distribution and use. The most recent revision is OMG SysML v. 1.6 (see SysML Specifications page).

Further Info: For more information about the SysML language details, training, tutorials, and resources, check out the SysML Forum web. For more information about the MBSE process details, training, tutorials, and resources, check out the MBSE Works web.

Once you make a decision to use SysML as the common specification language for your MBSE team or project, you are faced with the choice of using a drawing tool (e.g., MS Office Visio, OpenOffice Draw, GIMP) or a bona fide modeling tool to capture your MBSE work artifacts. What's the difference between a drawing tool and a visual modeling tool? While a drawing tool may provide you with a tool template that contains SysML syntax ("boxes and lines"), it isn't generally expected to enforce SysML "book-keeping" operations, which include, but are not limited, to the following:

• enforcement of syntactic (notational) and semantic well-formedness rules;
• support for large-scale model management and team modeling;
• support for bi-directional requirements traceability;
• support for simulations of Activity and Parametric diagrams
  

So if you are modeling-in-the-small, and are only interested in using SysML to sketch simple models for a small (a dozen or fewer) Systems Engineers, you may find a drawing tool, such as Visio, sufficient for your needs. However, if you need to capture the functional analysis or architecture of a complex system or system-of-systems, your MBSE team will greatly benefit from the use of a bona fide SysML modeling tool!