Presentation given to the INCOSE UK Model Based Systems Engineering Working Group

1. The 5 Principles of MBSE 1
The 5 Principles of Model Based Systems
Engineering
James Towers
Object Flow Ltd
Chair INCOSE UK MBSE Working Group

2. The 5 Principles of MBSE 2
The 3 Evils
(from Holt & Perry)

3. The 5 Principles of MBSE 3
1 – A Lack of Understanding (Unknown Unknowns)
 Applies to both individuals and
organisations (projects)
 The dip in productivity
corresponds with the body of
the “Brontosaurus of
Complexity” (Holt & Perry)
 “There are unknown unknowns
– there are things we do not
know we don't know” (Donald
Rumsfeld)

4. The 5 Principles of MBSE 4
 We often use the word complex as a synonym for ‘difficult’ or ‘no
recognisable pattern’
 We should make a distinction between how we define structures and
behaviour
 We can define at least 4 different behaviours of systems
 Simple = easily knowable
 Complicated = not simple, but still knowable
 Complex = not fully knowable, but reasonably predictable
 Chaotic = neither knowable nor predictable
 Each of the 3 spaces (Problem, Solution & Project) can behave in a
different way (and at different points in time)
2 - Complexity
(Plus Simplicity, Complicated and Chaotic)

5. The 5 Principles of MBSE 5
The 3 Spaces
Problem
Space
Defines the Problem or
Opportunity
e.g. User Requirements
Specifics the Solution
e.g. System Requirements
Shapes the Activity
The Organisations, People,
Processes, Standards and
Tools used to perform the SE
Activity
Solution
Space
Project
Space
Time

6. The 5 Principles of MBSE 6
Cynefin Sense Making Framework

7. The 5 Principles of MBSE 7
3 - Communication - I don’t know what you need to
know
 We can’t rely on a process to
tell us what artefacts to produce
and who to give them to
 We can’t rely on request -
response protocols because
other stakeholders in the
project may not even know we
exist, let alone what information
we have or require

8. The 5 Principles of MBSE 8
The 5 Principles

9. The 5 Principles of MBSE 9
bdd [Package] Model, View & Diagram [Model & View]
«block»
Model
«block»
View
«block»
Model element
«block»
View element
«block»
Diagram
«block»
System
«block»
Graphical Symbol
«block»
Text
«block»
Mathamatical
Language
«block»
Architecture
«block»
Matrix
«block»
Table
«block»
Text Document
Name: Model & View
Author: James Towers
Version: 1.0
Created: 09/09/2013 18:59:04
Updated: 06/10/2013 16:28:29
1
abstracts
1..*
1..*
represents
1
1..*
is a projection of
1
1..*
1
1..*
1
1..*
1
0..*
is related to
0..*
1 – Modelling is more than just drawing

10. The 5 Principles of MBSE 10
 There’s a temptation when building models to first model everything
you know and then model everything you discover
 It’s important to remember that every model is in someway
incomplete, and it’s this incompleteness that makes it valuable (See
Principle 3). Knowing what to omit requires you to know what its
purpose is
 If someone wanted to know how far it was from Tooting Bec to Edgware
then consulting the Tube map would be pointless (it wasn’t built for that
purpose)
 Purposes include Synthesis, Analysis, Specification, Communication
and others
 Scopes include the Problem, Solution and Project Spaces and others
2 – Each View has a defined purpose and scope

11. The 5 Principles of MBSE 11
 The Model is insightful:
 It can be queried in ways unconnected sources can’t.
 It can be navigated, thus allowing us to discover its content without prior
knowledge of what to expect.
 The Model is more accessible, quicker, cheaper, controllable,
adaptable or less risky (in a safety, security and financial sense) to
construct and/or interrogate than the real world.
 The Model is pragmatic:
 The degree to which it conforms to any of these principles is decided based on risk.
3 – The Model adds value

12. The 5 Principles of MBSE 12
 The Model is:
 Concise -
 It records one fact in one place (Model Element)
 Consistent -
 It doesn’t contradict itself
 Coherent -
 Its parts produce a unified whole
 Correct –
 It can be Verified and Validated based on defined criteria
 It uses abstraction to allow imprecision without inaccuracy
4 – The Model is of sufficient quality

13. The 5 Principles of MBSE 13
 Where appropriate the Model is constructed using recognisable and
documented patterns
 May be public or proprietary, general or domain-specific
 The Model uses the most appropriate languages, paradigms &
topologies
 Languages may include natural language (text), mathematics, general
purpose graphical languages (UML, SysML), domain-specific languages
and others
 Paradigms may include functional, object-oriented, symbolic, logical and
others
 Topologies may include graphs, trees, matrices, tables, natural-language
(requirements boilerplates) and others
5 – The Model is constructed from the most
appropriate elements

14. The 5 Principles of MBSE 14
The 4 Enablers

15. The 5 Principles of MBSE 15
 May be public or proprietary, general or domain-specific
 Architectural Frameworks enable MBSE by:
 Ensuring the Model is coherent and consistent, by providing architectural
rules and syntax
 Help us manage complexity and clarify what is important by the use of
information portioning and hiding
 Helps us identify omissions
 Provides traceability & navigability
 Aids communication as may be common across multiple projects
 Define ontologies and standardises concepts
1 - Architectural Frameworks

16. The 5 Principles of MBSE 16
 Process Frameworks provide guidelines and principles that allow us
to generate a customised process
 Where appropriate the Enterprise uses recognisable and
documented process patterns
 The Project Team follows a defined System Engineering Process
based on one or more of the Process Frameworks
 All activities within the process involve the Model.
 All newly discovered Systems Engineering knowledge is recorded in the
Model.
 The Model is shared in a controlled manner
 Configuration / Version Control
 Access Control – although the default is open
2 - Process Frameworks

17. The 5 Principles of MBSE 17
 The People involved have the appropriate competencies
3 - People
Complexity
(Cynefin)
Practices Work Type Skill Level Hot to
Achieve
Simple Best “Assembly Line” Proficiency Training
Complicated Good Information Fluency Training &
Expereince
Complex Emergent Knowledge Literacy Deliberate
Practice
Chaos Novel Concept Mastery Deliberate
Practice
(10,000 hrs)

18. The 5 Principles of MBSE 18
 The tools used have the appropriate capabilities
 There is a single Model of the System Under Consideration (SUC) i.e.
they’re modelling not drawing tools
 They support the required languages, paradigms and topologies and
ideally (where possible) can translate between them
 They support open standards and data formats
4 - Tools

19. The 5 Principles of MBSE 19
Questions

20. The 5 Principles of MBSE 20
 Thanks to the following for their contributions, either directly of via
published work
 Tom Riley (Thales)
 Jon Holt and Simon Perry (Atego)
 Dave Snowden (Cognative Edge)
Acknowledgments