Professor John Hosking,

Dean of Engineering and Computer Science

Models, Modelling, MBSE

Models and modelling

Formalisation

language syntax/semantics

Scope of applicability

Insight

Execution

Prediction

v = u + at

v2 = u2 + 2as

s = ut + ½at2

Models and modelling

Formalisation

language syntax/semantics

Scope of applicability

Insight

Execution

Prediction

CH4 + 2 O2 -> CO2 + 2 H2O

Models and modelling

Formalisation

language syntax/semantics

Scope of applicability

Insight

Execution

Prediction

Models and modelling

Formalisation

language syntax/semantics

Scope of applicability

Insight

Execution

Prediction

Models and Engineering

• Engineering is about modelling– Including Software Engineering– Much of the engineering process is about taking a

specification and turning it into design model(s)• Using theory, methodology, evidence based best practice

– Models are tested • scope of applicability• compliance to specification

– Models are used to specify detailed construction– Construction overseen by engineers

• true for SE?

Modelling and Software Engineering

“The growing complexity of software is the motivation behind work on industrializing software development. In particular, current research in the area of model driven engineering (MDE) is primarily concerned with reducing the gap between problem and software implementation domains through the use of technologies that support systematic transformation of problem-level abstractions to software implementations.”

France and Rumpe,2007, Model-driven Development of Complex Software: A Research Roadmap, FOSE’07

MDE is about CommunicationProblem Domain

Implementation DomainModel

Test Models

Design Model

Problem Domain

Implementation Domain

Req Model

Design Models

Analysis Model

Test ModelsWhat modelling language(s)?

How are they designed to be effective?How are they implemented?

MDE is about Viewpoints

Test Models

Design Model

Problem Domain

Implementation Domain

Req Model

Design Models

Analysis Model

Test Models

Separation of concerns

Consistency management

Hidden dependencies

MDE is about Automation

Test Models

Design Model

Problem

Domain

Implementation Domain

Req Model

Design Models

Analysis Model

Test Models

Anti Patterns?

Coverage?

Self Consistent?

Code Smells?

Deadlocks?

Performance?Auto/semi-autotransform

Transform Model

Transform specn?Traceability links?Consistency?Versioning?

Analysis tool scope?Limitations?

Usability?Specification/implmn

MDE Challenges

“… we consider the problem of developing MDE technologies that automate significant portions of the software lifecycle to be a wicked problem. A wicked problem has multiple dimensions that are related in complex ways and thus cannot be solved by cobbling solutions to the different problem dimensions.”

France and Rumpe,2007, Model-driven Development of Complex Software: A Research Roadmap, FOSE’07

MDE and Formal Methods

• Why not just use formal specification techniques?– FSTs typically limited in scope

• Eg only work for some viewpoints

– Tradeoff in expressability and ability to mechanically analyse

– Hence use FSTs to analyse subset of models• Eg Z models for data and operation viewpoints• “Model checking” for state transition viewpoints• Petri nets for control flow viewpoint

Development versus Runtime Models

• Most MDE initiatives have focused on development models– Abstractions above code

• Runtime models present abstractions of executing systems– How to use to manage and modify executing software

• Adaptive systems – monitor behaviour (eg performance) and adapt (eg add extra servers)

Some major MDE initiatives

• Model Driven Architecture (MDA) - OMG– Three viewpoints: computation independent, platform

independent and platform dependent– MOF, UML, QVT– Very rich set of modelling languages lots of complexity– Example of “extensible general purpose modelling language”

approach

• Software factories – Microsoft– Many small domain specific viewpoints linked by transforms– Small lightweight modelling languages– Heavy emphasis on reuse of knowledge– Example of “domain specific modelling language” approach

Pros and cons

Extensible GPML

+ “Standard” models

+ Model interchange

+ Analysis tool interchange

+ Build it once- Complex languages- Not client friendly- Extension mechanisms

complicate things

Domain Specific MLs

+ Client friendly

+ Simple languages

+ Simpler tooling- Build it often- Smaller user base =>

higher maintenance cost- DSL Babel challenge

Model Driven Systems Engineering

• Extends from Software Engineering to Systems Engineering

• Typically Extensible GPML based– Heavy emphasis on standardisation– Not surprising

• Egs– SysML– Function Blocks (more for embedded systems)– BIM/IFC (for integrated design of buildings)

SysML

• OMG driven (UML standards developers)• Extends/restricts UML (ie GPML approach)

– New viewpoints• Requirements, Parametric views• Supports V&V, gap analysis

– Eliminates some software centric viewpoints• Only uses 7 of UML 2’s 13 diagrams• Replaces “classes” with “blocks”

IEC 61499 Function Blocks

• From Control community• Pushes Block concept in SysML further

– Gaining popularity in embedded systems community

– Arguably more implmnoriented than SysML

– See Vyatkin review paper– Argues for combining

BIM IFC

• Building information modelling– Integrates viewpoints of multiple professionals working on

constructing/maintaining buildings• Engineers, PMs, architects, builders, plumbers, …

– Aims to revolutionise building construction– Current state of the art – much manual re-entry of data

• Significant opportunity for error• BIM aims for standardised interoperability

• Industry Foundation Classes– Base set of classes defining the multiple viewpoints– EXPRESS modelling language extensible GPML approach

• Much work done – much to do

Summary

• Models and their importance in Science and Engineering

• MDE basics• Issues with MDE and examples of initiatives• MD Systems Engineering approaches