INCOSE UK: MBSE - is there any substance behind the hype?

Copyright © 2013 by Object Flow Ltd. Published and used by INCOSE UK Ltd and INCOSE with permission.

MBSE – is there any substance behind the hype?

James Towers Principal consultant -‐ Object Flow Ltd Chair – INCOSE UK Model Based Systems Engineering Working Group

INCOSE UK Railway Interest Group, October 2013


IntroducPon

•  Model-‐based Systems Engineering (MBSE) is generaPng a great deal of interest within the SE community -‐ at recent INCOSE InternaPonal Symposia, there has been standing room only at MBSE presentaPons. The UK Chapter set up an MBSE Working Group in 2012. Right from the very first meePng it became apparent that: –  The term MBSE is not very well defined or understood. –  Some Systems Engineers hold the view that there is no (or liYle)

disPncPon between MBSE and what they refer to as “Good Systems Engineering”.

–  Many Systems Engineers currently uPlise diagrams and simulaPons in their work but do not consider they are doing MBSE, so what's the difference?

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Quotes

•  “Essen3ally, all models are wrong, but some are useful.” –  George Box, Empirical Model-‐Building and Response Surfaces (1987)

•  “Experience by itself teaches nothing...Without theory, experience has no meaning. Without theory, one has no ques3ons to ask. Hence without theory there is no learning.” –  W. Edwards Deming, The New Economics for Industry, Government, Educa3on (1993)

•  “Un bon croquis vaut mieux qu'un long discours.” (A good sketch is beUer than a long speech.) –  Napoléon Bonaparte, Quoted in L'Arche de Noé (1968) by Marie-‐Madeleine Fourcade

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Roles & OrganisaPons

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class Roles & Organisations

Person

Name: Roles & OrganisationsAuthor: James TowersVersion: 1.0Created: 03/10/2013 09:29:10Updated: 03/10/2013 10:20:36

Role Organisation

Context

1..*

Comprises

11..*

Fills

0..*

1

0..*

Consider the following concepts and relationships:


About me

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object About Me - James Towers

James Towers :Person

Network Rail :Organisation

Functional Modelling Analyst :Role

WCRM Systems Engineering :Context

Principal Consultant :Role

Object Flow Ltd :Organisation

Worked for Nigel Best within Brian Halliday's department

Helping organisations implement model based techniques

Name: About Me - James TowersAuthor: James TowersVersion: 1.0Created: 03/10/2013 10:06:17Updated: 03/10/2013 13:46:48

2004 - Present :Context

INCOSE UK MBSE WG :Organisation

Chair :Role

2012 - Present :Context


About the MBSE WG

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uc MBSE WG Context (Syndicate Group)

MBSE WG Context

Name: MBSE WG Context (Syndicate Group)Author: Camm, Capel, Fletcher, Holt & Older Version: 1.0Created: 01/02/2013 17:16:33Updated: 02/10/2013 10:11:02

Promote MBSE

Apply Cross Industry

People, Processes & Tools

Industry

Industry Group

Profesional Body

Disseminate Prov ide Knowledge About

Publish Present ...Research ...Tools ...Best Practice

Academia Standards Organisaton

Current Practice

Identify Current Practice

Ev aluate Current Practice

Define Business Case

«include»

«constrains» «include»

«constrains»

«constrains»

«include»


Mission Statement

•  The aims of the MBSE WG are to: –  Promote the use and understanding of MBSE, –  Facilitate and improve communicaPon between System Engineers pracPcing MBSE,

–  IdenPfy and catalogue the Tools, Techniques and Languages used,

–  Provide guidance on how to best apply MBSE techniques across the lifecycle, and

–  Support the MBSE IniPaPve run by INCOSE Central and the OMG.

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ParPcipaPng OrganisaPons

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Flowobject:Helping to build better Systems


WHAT IS MBSE? QuesPon 1

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Z9 – “What is Model Based Systems Engineering”

•  INCOSE UK guide Z9 defines MBSE as: –  The formalised applicaPon of modelling to support:

•  System requirements •  Analysis •  Design •  V&V acPviPes

–  Beginning in the conceptual design phase and conPnuing throughout development and later lifecycle phases.

•  Also: –  MBSE is a model-‐centric approach providing a single point of truth which is reflected in a

set of living artefacts.

(Z9 can be downloaded from the INCOSE UK website)

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MBSE is a Philosophy

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class MBSE Philosophy

Name: MBSE PhilosophyAuthor: James TowersVersion: 1.0Created: 03/10/2013 15:19:54Updated: 06/10/2013 15:30:55

PhilosophyContext

Systems Engineering Project

PrincipleProblem Solution

MBSE

MBSE defines a set of Principles, which shape the Solutions, that are chosen to resolve the Problems, of a Systems Eng ineering Project.

MBSE is a kind of SE

SE

SE is a kind of Philosophy

0..*

shapes

1..*1..*

chosen to resolve

0..*

0..*

1..*

1..*

defines a set of

1..*

0..*

relates to

1..*


What does this mean?

•  SE Projects can’t be divided into “model based” and “not model based”, but rather more-‐or-‐less model based, depending on their conformance to the principles of MBSE.

•  Every project is different, and therefore if you believe in the principles of MBSE you sPll have to make your own difficult decisions based on those principles. MBSE won’t tell you what to do.

•  The principles of MBSE aren’t complete, they only augment the exisPng principles of Systems Engineering.

•  As a philosophy MBSE has it’s fair share of high priests, soothsayers (including cassandras) and zealots.

•  To successfully implement MBSE within an organisaPon requires a cultural shir, which shouldn’t be underesPmated.

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WHAT IS A MODEL? QuesPon 2

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What is a model?

•  A model is “an abstrac3on of reality” such as: •  Our thoughts, •  This presentaPon, •  An Airfix kit, •  A requirements catalogue, and •  A concept of operaPons document.

–  However this definiPon is too general to be of use here. –  Using this definiPon all SE projects would be model based.

•  which in some sense they are!

•  At the other extreme ‘models’ are somePmes confused with ‘diagrams’. So what’s the difference?

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Models & Views

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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..*

Single underlying definition

Multiple representations


Principles of a SE Model

•  It is complete and consistent. –  Each ViewElement relates to 1 and only 1 ModelElement (DefiniPon) –  You can use one view to validate another.

•  While it may be imprecise it should never be inaccurate. –  The ability to begin with imprecise (abstract) concepts and refine them as the model

progresses allows us to handle the uncertainty and complexity of a SE project.

•  It is insighvul. –  you can query it in ways that you couldn’t query unconnected sources or even the most

knowledgeable Systems Engineer. •  This requires explicit relaPonships between ModelElements •  It’s harder to achieve when you have mulPple repositories.

•  Each view is presented using the most appropriate language, paradigm and topology. –  It’s not just UML/SysML but also text, maths, rich pictures or whatever is appropriate.

•  Each view has a defined viewpoint (purpose). –  InformaPon not relevant to a view is excluded from that view.

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The Challenge of MulPple Repositories

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Appropriate Language

•  Every language (graphical, mathemaPcal or textual) is built on a paradigm. –  There will always be some concepts it is impossible (or at least difficult) to represent

using a given language. •  This problem is compounded if the modeller has a limited experience and/or vocabulary of that language.

–  Natural language has a plethora of concepts which we are constantly expanding plus imprecise definiPons which we frequently overload.

•  Techniques like EARS (Easy Approach to Requirements Syntax) are designed to overcome the problems with natural language.

•  Languages with a simple well defined structure help us to manage complexity. –  if this structure is an inherent property of the language rather than a set of rules we apply then we

have one less thing to worry about.

•  ‘Rich’ models uPlise the most appropriate features of mulPple languages.

“The problem with the French is that they don't have a word for entrepreneur.” – Erroneously credited to President G W Bush

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Graphical Languages

Graphical Language

Immediacy of

interrogaPon

Freedom of InspecPon

MulP-‐dimensional

Clear disPncPon of concepts

Easy paYern recogniPon

Can be animated

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People

•  It’s not sufficient just to know the constructs of a (modelling) language as you also need to know it’s paYerns and convenPons. –  But wherever you idenPfy these you should make them explicit.

•  You need a good understanding of the modelling principles as for many of the problems you encounter you will be a pioneer. –  Although at the same Pme support from experienced people can stop you from

reinvenPng the wheel.

•  In order to choose the most appropriate technique you have to understand mulPple languages, paradigms and topologies. –  "I suppose it is temp3ng, if the only tool you have is a hammer, to treat everything as if it

were a nail.” -‐ Abraham H. Maslow (1966). The Psychology of Science

•  Every Systems Engineer has to be a modeller. –  If the model is to be ‘a single point of truth’ it needs to be a collaboraPve effort which

meets the needs of all the stakeholders.

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Processes

•  Every SE acPvity should reference the model and result in an iteraPon of the model. –  As it may not be immediately clear how this would work it requires a cultural

shir for any SE organisaPon.

•  The MBSE Principles do not negate the need for an effecPve SE Process. •  AddiPonal Model related aspects will be needed.

–  As with all artefacts the model should be under version / configuraPon control. –  There will be addiPonal administraPon effort required, integraPon, security etc.

•  Where a more model-‐based organisaPon interfaces with a less model-‐based one there will be a need for translaPon at the boundary. –  It’s worth doing though as it will provide a greater degree of verificaPon for the inputs. –  If any organisaPon is insistent on the receipt of text based specificaPons as input it’s

possible to auto generate these from graphical models. •  Although, “be careful what you wish for”.

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Tools

•  MBSE Requires tools with the right capabiliPes. –  They must incorporate the disPncPon between the model and

mulPple views. –  They must be able to present the model using appropriate languages,

paradigms and topologies.

•  Where mulPple tools are unable to use a single model then: –  Some level of integraPon is desirable. –  May require manual configuraPon control. –  You may need to make a trade-‐off between ‘single point of truth’ and

‘appropriate language’. •  You may be doing this now if you model ‘everything’ in a single requirements

catalogue.

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Conclusions

•  The construcPon of a model as a ‘single point of truth’ gives us a powerful mechanism to mange the complexity of informaPon and query such informaPon in ways that are not otherwise possible. –  We already see this to some extent with catalogues of requirements.

•  By uPlising ‘appropriate languages’ we can use the inherent structure of the language to further manage complexity and uncertainty. –  Challenges due to the limitaPons of a language, paradigm or topology can be avoided. –  No need to implement structured frameworks like RQ boilerplates. –  Elements are always presented in a context which aids comprehension. –  InformaPon may be hidden when not relevant through the use of views.

•  ImplemenPng such a strategy is not easy and requires commitment on the part of the organisaPon plus the appropriate tools, procedures and skilled individuals.

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Contact Details

•  james.towers@object-‐flow.com

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Flowobject:Helping to build better Systems


Disclaimer

The ideas presented within this presentaPon are an evoluPon of the authors recent submission to the MBSE working group, and as such represents his personal viewpoint and not that of the MBSE working group.

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INCOSE UK: MBSE - is there any substance behind the hype?

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