An Introduction to Model-Based System Engineering (MBSE) and model value

Contents:

Model-Based System Engineering (MBSE) is the formalized application of modelling to support system requirements, design, analysis, verification and validation activities beginning in the conceptual design phase and continuing throughout development and later life cycle phases. MBSE with Arcadia method provides a guided step-by-step to all that are looking to develop systems that meet stakeholder needs aiming at reducing cost and risk.

Value of a model

A model helps to understand the growing systems complexity by breaking down systems into simpler constructs that can be understood.

Tackle the lack of understanding of the initial needs not fully analysed in different contexts.

Removes communication problems by using of a common language (i.e., modelling language) to address communication problems, across spoken language barriers and backgrounds.

Encourages and improves interaction with project stakeholders and all engineering disciplines.

Improves quality as it implements:

  • Rigorous requirements traceability.
  • Facilitates the system design integrity; enhanced design changes detection and update across different areas.
  • Improved requirements specification and allocation to subsystems.
  • Early identification of requirements issues.
  • Consistent documentation, both within and across projects.

Ability to detect defects earlier in the system development cycle with:

  • On-going requirements validation through design verification and the use of simulation and automatic verification, increases confidence, reduces risk and costs.
  • Helps to verify the system correctness (e.g., interfaces captured and defined, data flow type is correct).
  • Helps to verify system completeness (e.g., all modes and states identified and defined), consistency and correctness with fewer changes.

Improves productivity:

  • Reuse of existing models to support design and technology evolution.
  • Automated generation of documentation.

System aspects that can be modelled


When a model activity is undertaking two aspects of the System can be captured:

  • Structural aspect: the ‘what’ of the System; it captures what elements a system is made of (e.g., it helps to define the product breakdown structure – PBS) and the relationships between the elements.
  • Behavioural aspect: the ‘how’ of the System; how the system elements behave, how elements interact with one another and under what conditions.

A good modelling approach must always consider both the ‘what’ and the ‘how’ regardless of the System, even if we are considering a system such as a database, there is the need to consider how the various stakeholder behave towards it.

When should be considered to model

Modelling can be applied at any product or service stage development. Some examples are captured below (not an extensive list):

  • Modelling can be applied whenever there is the need to understand a system or something.
  • Modelling can be applied within a small-medium enterprise (SME), start-up or big organisations.
  • Modelling can be applied at any point in the Life Cycle, for example, stakeholder needs elicitation by doing “quick and dirty” iterations and scenarios explorations or at later and more detailed development stages.
  • Modelling efforts should be applied when only adding value.

Considerations when preparing for MBSE modelling

There are aspects that need to be considered when doing modelling activities: tools, language or notation and people. All this aspects need also to consider planning and scope of a modelling effort as described in the Planning for success with MBSE Arcadia.

Tools

As a model is not merely a collection of representations, but an integrated repository of project knowledge, one or more tools are typically required. These tools must not only provide the necessary capability in terms of language support but should also integrate with each other to ensure completeness, correctness, and consistency across the project.

Language or notation

Standard Techniques and Representations MBSE is most effective when standard techniques and representations are employed. The use of standards improves consistency and facilitates interoperability of tools, people, and process.

People

It is good practise to ensure the appropriate capabilities in modelling languages and tools does not have to be limited to project personnel. MBSE provides the maximum benefit when no translation of the model is required for the stakeholders, Training and support must be provided.

What MBSE is not

Quite common there are myths around MBSE. Hereafter, it will be presented what MBSE is not.

Arcadia / SysML

A representation should use the most appropriate notation for the project. Arcadia and SysML are a very powerful modelling language, however, other languages (e.g., textual, mathematical) also exist and should be chosen on their individual merits.

Simulation

A representation can be either static or dynamic (simulation). Simulation enhances and provides automated and early defects detection.

Part of Systems Engineering activities required on a project

MBSE is an integrated approach to Systems Engineering in which all activities should reference a single point of truth, the model, in order to realise the maximum benefits.

Drawing

A representation (whether graphical, textual, or other) should be connected to the underlying model in order to realise the maximum benefits of MBSE (correctness, completeness, and consistency).

Modelling is MBSE

Modelling forms the core of MBSE, but not all Models are MBSE Models. Modelling and Model-based Engineering (MBE) is extensively in engineering. MBE can be applied to other engineering areas, such as design, and use of bespoke modelling Notations (circuit diagrams, 3-D modelling, CAD, etc.). MBSE, is applied at a higher level and will often be used to harmonise the MBE activities to ensure that the overall System satisfies its original need.