Dov Dori © 2015

Dov DoriMassachusetts Institute of TechnologyTechnion, Israel Institute of Technology

SDM WebinarFebruary 9, 2015

To Model or Not to Model? Formalizing the ConceptualModeling Thought Process to Benefit Engineers and Scientists

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How do we explain ideas to each other? Grab a pen and piece of paper, or a chalk and

blackboard Scribble shapes with names next to them While talking, run lines with or without arrows

among the shapes Follow the reaction of the audience to see if

idea is understood Answer questions, continue scribbling…

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What is Conceptual Modeling? A systematic, formalized process of describing,

specifying, designing or explaining ideas, systems, products or processes through a model.

Applicable to both Science – Studying what is known and what is

missing to satisfy human thirst for knowledge, and Engineering – Designing systems to benefit

humans, based on sound scientific principles

Science can be thought of as reverse engineering of nature

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Convert tacit, fragmented knowledge into explicit, integrative knowledge.

Construct concise models – mental pictures of natural systems [science] and artificial systems [engineering]

while integrating structure and behaviour at all detail levels.

Communicate the model to stakeholders through formal, unambiguous, actionable descriptions.

Why Conceptual Modeling?

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What is required of a conceptual modeling language?

It must be:Simple yet expressive Intuitive yet formal

Seemingly contradicting requirements!

How can these be reconciled?

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A conceptual modeling language that is simple yet expressive,

and intuitive yet formal

Let the search begin!

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Preamble: OCCUM’s RAZOR

"If you have two equally likely solutions to a problem, choose the simplest."

"Entities should not be multiplied unnecessarily." "Entia non sunt multiplicanda praeter necessitatem"

14th Century logician and Franciscan priest William of Ockham

In an extended version:

OCCUM’s RAZOR is an important guiding principle of OPM

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Theoretical Foundation 1:Three Cognitive Assumptions

(1) Dual-channel processing – humans possess separatesystems for processing visual and verbalrepresentations (Clark & Paivio, 1991; Baddeley, 1992).

(2) Limited capacity – the amount of processing that can take place within each information processing channel is extremely limited (Miller, 1956; Chandler & Sweller, 1991; Baddeley, 1992).

(3) Active processing – meaningful learning occurs during active cognitive processing, paying attention to words and pictures.

Mayer, R.E. (2003). The promise of multimedia learning: using the same instructional design methods across different media.

Learning and Instruction, 13, pp. 125-139.

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The design of Object- Process Methodology –OPM accounts for the three Cognitive Assumptions

Communications of the ACM, 2008

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Theoretical Foundation 2:Universal Ontology

Ontology: a set of concepts for describing a domain (industry, banking, military, botany, healthcare…) and systems within it.

Universal Ontology: a domain-independent set of concepts for describing systems in the universe, both natural and man-made.

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OPM Design Principle 1: Simplicity Simplicity is a must for modeling systems We cannot ignore the inherent

complexity of systems.However, We can simplify the way systems are

modeled without sacrificing accuracy, and without sparing details.

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If the same system can be expresses by two languages with the same level of fidelity, the one with the shortest description is preferred. Inspired by The Minimum Description Length

(MDL) Principle (Rissanen 1978)

OPM Design Principle 2: Minimum Description Length

Rissanen, J. (1978). Modeling by shortest data description. Automatica, 14: 465-471.

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Fundamental question 1:What is needed to describe the universe?

Answer: Describing the universe requires things and relations among them.

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Question 2:What can these

things “do”?

Answer: Things can exist or happen.

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Question 3:What are the things that exist

in the world?

Answer: Objects exist.They are static.

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Question 4:What are the things that happen in the world?

Answer: Processes happen.They are dynamic.

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Question 5: How do objects and processes relate?

Answer: Processes happen to objects.While happening,processes transform objects.

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© 2006-7 Prof. Dov DoriDov Dori © 2015

OPM Things: Objects and Processes

Object: A thing that exists or might exist physically or informatically.

Process: A thing that transforms one or more objects.

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Physical vs. Informatical Things

© 2006-7 Prof. Dov DoriDov Dori © 2015

OPM’s only two building blocks:

1. Stateful Object2. Process

All the other elements are relations between things, expressed graphically as links.

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A process (even a physical one) is a cognitive pattern, in which we: compare an object existence, or its state,

in time points in the past vs. now, and use this data to create a mental picture of

the transformation the object undergoes. Only the objects involved in a physical

process can be “touched”

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Transform? What does that mean?

Transforming means creating an object or destroying an object or affecting an object.

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© 2006-7 Prof. Dov DoriDov Dori © 2015

Transforming an object by a process can be done in three ways

(1) Process consumes the object

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(2) Process creates the object

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Affecting? What does that mean?

A process affects an object bychanging its state.Hence, objects must be stateful

– they must have states.

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© 2006-7 Prof. Dov DoriDov Dori © 2015

(3) Process changes object state:The third and last kind of object transformation:

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The three transformation kinds

Consumption:

Creation:

StateChange:

• OPM uses a single type of diagram –Object-Process Diagram (OPD)

• Graphic edit operations are translated on the fly to natural language –

Object-Process Language (OPL)

• Catering to dual channel processing

© 2006-7 Prof. Dov DoriDov Dori © 2015

The graphics-text equivalence OPM principleAny model fact expressed graphically in an OPD is also expressed textually in the corresponding OPL paragraph.

Caters to the dual channel cognitive assumption (Mayer, 2010)

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A process can transform an object by:•Consuming it •Creating it•Changing its state

The OPL text is created on the fly in response to each graphic editing operation.

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What are the two major aspects of any system?

Structure – the static aspect: what the system is made of. Time-independent

Behavior – the dynamic aspect: how the system changes over time.Time-dependent

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What third aspect is specific to man-made systems?

Function – the utilitarian, subjective aspect:

Why is the system built? For whom is the system built? Who benefits from operating the system?

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The Object-Process Theorem

Stateful objects, processes,

and relations among them

constitute a necessary and

sufficient universal ontology.2/8/2015

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Two Complementary Proofs:

1. Theoretical, based on logic

2. Empirical, based on examples

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Theoretical Proof Part 1 - NecessityStateful objects and processes are necessary

to specify the two system aspects:• Specifying the structural, static system aspect

requires stateful objects and relations among them.

• Specifying the procedural, dynamic system aspect mandates using processes and relations between them and the objects they transform.

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Stateful objects and processes are sufficient to specify any thing in any system:

• Anything that exists or might exist can be specified in terms of stateful objects and relations among them.

• Anything that happens or might happen to any stateful object can be specified in terms of processes and relations between them and the object they transform.

Q.E.D.

Theoretical Proof Part 2 - Sufficiency

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Empirical Proof of the Object-Process Theorem Stateful objects, processes, and relations among them constitute a necessary and sufficient universal ontology.

If the ontology is universal, it can model systems in any domain.The empirical proof: Providing evidence of successful models from various, unrelated domains.

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Empirical Proof from Science: Molecular biology

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“Beyond the scientific value of these specific findings, this work demonstrates the value of the conceptual model as an in silico vehicle for hypotheses generation and testing, which can reinforce, and often even replace, risky, costlier wet lab experiments.”

© 2006-7 Prof. Dov DoriDov Dori © 2015

Tripped Pumps Cause

too high Pressure

Nuclear reactor failure: The Three Mile Island Accident

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Offshore Oil Well Drilling

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Airport Operations: Outgoing Passenger

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Iron Dome – an Israeli ballistic missile defense systemYaniv Mordecai and Dov Dori, Evolving System Modeling: Facilitating Agile System Development with Object-Process Methodology. SysCon 2015 ,9th

Annual IEEE International Systems Conference, Vancouver, Canada, April 13-16 2015.To be presented

2/8/2015

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Additional sample domains in which OPM has been used• Complex, Interconnected, Large-Scale Socio-Technical Systems. Systems

Engineering 14(3), 2011.

• Networking Mobile Devices and Computers in an Intelligent Home. International Journal of Smart Home 3(4), pp. 15-22, October, 2009.

• Multi-Agent Systems. IEEE Transactions on Systems, Man, and Cybernetics –Part C: Applications and Reviews, 40 (2) pp. 227-241, 2010.

• Semantic Web Services Matching and Composition. Web Semantics: Science, Services and Agents on the World Wide Web. 9, pp. 16-28, 2011.

• Project-Product Lifecycle Management. Systems Engineering, 16 (4), pp. 413-426, 2013.

• Model-Based Risk-Oriented Robust Systems Design. International Journal of Strategic Engineering Asset Management, 1(4), pp. 331-354, 2013.

• Medical Robotics and Miscommunication Scenarios. An Object-Process Methodology Conceptual Model. Artificial Intelligence in Medicine, 62(3) pp. 153-163, 2014.

• Modeling Exceptions in Biomedical Informatics. Journal of Biomedical Informatics 42(4), pp. 736-747, 2009.

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Animated simulation of the OPM model Caters to the active cognitive processing: meaningful learning occurs during active processing (Mayer, 2010)

Animated simulation is a prime visualization and conceptual debugging tool.

© 2006-7 Prof. Dov DoriDov Dori © 2015

Complexity Management with OPM Systems are inherently complex. To alleviate this complexity, in OPM, it is

managed by detail decomposition through three refinement-abstraction: In-zooming – Out-zooming Unfolding – Folding State expression – suppression.

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In-zooming – Out-zooming ExampleProcess Performance Controlling- a metamodel from ISO 19450

•All the OPDs, at any detail level, are self-similar.•They contain only stateful objects, processes, and relations.

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OPM Complexity Management Benefits There is no limit on the level of complexity of

the system being modeled: One can specify system structure and behavior at

any level of detail by recursively in-zooming. Catering to the cognitive limited capacity: Each diagram is not overly complicated.

All the diagrams are “aware” of each other: All OPDs are partial views of the same system. Any change in one diagram is propagated to all

the other relevant ones.

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Summary: OPM foundations• Simplicity and minimal ontology:• Stateful objects, processes that transform objects,

and relations among them

• The three cognitive assumptions:• Dual channel processing

• Graphics and equivalent text

• Limited cognitive capacity • Refinement abstraction mechanism

• Active processing• Animated simulation

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Summary: OPM Aspect UnificationThe three system aspects: Function (why the system is built), Structure (static aspect: what is the

system made of), and Behavior (dynamic aspect: how the

system changes over time) Are expressed bi-modally, in graphics and

equivalent text In a single model

© 2006-7 Prof. Dov DoriDov Dori © 2015

Summary: OPM universality• OPM is a universal formal yet intuitive

language for conceptual modeling of systems• From any engineering or science domain• At any level of complexity• Unifies function, structure, and behavior in a

single model.• OPM is the new ISO 19450

• Soon freely downloadable as ISO Publically Available Specification

• Free OPCAT software now downloadable from http://esml.iem.technion.ac.il/

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OPM Resources:

• Book: Object-Process Methodology - A Holistic Systems Paradigm, Springer Verlag, Berlin, Heidelberg, New York, 2002.

• Website: Enterprise Systems Modeling Laboratory contains• journal & conference

papers, • free OPCAT software,• presentations, • projects, and more.

© 2006-7 Prof. Dov DoriDov Dori © 2015

Questions and (hopefully) Answers

Join the growing OPM community Here!https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=OPM&A=1

Contact: Dov Dori – dori@mit.edu

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Essence and Affiliation Essence pertains to the thing’s nature: denotes whether the thing is physical or

informatical. Affiliation pertains to the thing’s scope: denotes whether the thing is systemic, i.e. part of

the system, or environmental, i.e. part of the system’s environment

The Essence-Affiliation attribute value combinations

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Cyber-Physical Systems: Characteristics Software-controlled physical systems Include physical and cybernetic components An agent – a human decision-maker or an

information & decision-making system – is the cybernetic component

Hardware (motors, actuators, VLSI chips…) is the physical component

Physical processes signal and induce cybernetic events

Cybernetic processes signal and induce physical events

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Essence is key to modeling Cyber-Physical systems

Physical objects in the model represent what is really “out there” – actual states and values of objects

Informatical objects represent information about their corresponding physical objects

Only informatical objects are available to a decision making agent (human or artificial)

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Cyber-Physical GapA cyber-physical gap exists when the state of the informatical object incorrectly indicates the state of the physical object is supposed to represent

© 2006-7 Prof. Dov DoriDov Dori © 2015

The cyber-physical gap – a critical factor in modern systems design

• It must be accounted for when designing systems, notably safety-critical ones

• OPM is most suitable for modeling cyber-physical gaps

• This is due to its notion of essence –physical vs. informatical things

© 2006-7 Prof. Dov DoriDov Dori © 2015

First cyber-physical gap –Incorrect instrument reading:

PORV is (stuck) open, but due to the false PORV closed indication, the Crew determines

PORV is closed!

A critical conflict between reality and its cybernetic mirroring!

Full presentation in http://www.csdm2014.csdm.fr/-Program-.html#13

Cyber-physical gap example:Three-Mile Island Accident

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Appendix: SysML and OPM – a brief comparison Feature SysML OPM

Theoretical foundation UML; Object-Oriented paradigm

Minimal universal ontology;

Object-Process Theorem

Standard documentation

number of pages

1670 (700 + 700 + 270)

130(100 + 30)

Standardization body OMG (2006) ISO (2014)Number of diagram

kinds 9 1

Graphic modality yes yesTextual modality no yes

Physical-informatical distinction no yes

Systemic-environmental

distinctionno yes