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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
The 5 Principles of MBSE 2
The 3 Evils (from Holt & Perry)
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)
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)
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
SolutionSpace
ProjectSpace
Time
The 5 Principles of MBSE 6
Cynefin Sense Making Framework
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
The 5 Principles of MBSE 8
The 5 Principles
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 & ViewAuthor: James TowersVersion: 1.0Created: 09/09/2013 18:59:04Updated: 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
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
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
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
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
The 5 Principles of MBSE 14
The 4 Enablers
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
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
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)
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
The 5 Principles of MBSE 19
Questions
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
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