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

Transcription

1 To Model or Not to Model? Formalizing the Conceptual Modeling Thought Process to Benefit Engineers and Scientists Dov Dori Massachusetts Institute of Technology Technion, Israel Institute of Technology SDM Webinar February 9, 2015

2 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 2

3 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 3

4 Why Conceptual Modeling? 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. 4

5 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? 5

6 A conceptual modeling language that is simple yet expressive, and intuitive yet formal Let the search begin! 6

7 Preamble: OCCUM s RAZOR 14th Century logician and Franciscan priest William of Ockham "Entities should not be multiplied unnecessarily." "Entia non sunt multiplicanda praeter necessitatem" In an extended version: "If you have two equally likely solutions to a problem, choose the simplest." OCCUM s RAZOR is an important guiding principle of OPM 7

8 Theoretical Foundation 1: Three Cognitive Assumptions (1) Dual-channel processing humans possess separate systems for processing visual and verbal representations (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

9 Communications of the ACM, 2008 The design of Object- Process Methodology OPM accounts for the three Cognitive Assumptions 9

10 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. 10

11 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. 2/8/

12 OPM Design Principle 2: Minimum Description Length 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) Rissanen, J. (1978). Modeling by shortest data description. Automatica, 14: /8/

13 Fundamental question 1: What is needed to describe the universe? Answer: Describing the universe requires things and relations among them. 2/8/

14 Question 2: What can these things do? Answer: Things can exist or happen. 2/8/

15 Question 3: What are the things that exist in the world? Answer: Objects exist. They are static. 2/8/

16 Question 4: What are the things that happen in the world? Answer: Processes happen. They are dynamic. 2/8/

17 Question 5: How do objects and processes relate? Answer: Processes happen to objects. While happening, processes transform objects. 2/8/

18 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 Prof. Dov Dori 18

19 Physical vs. Informatical Things 19

20 OPM s only two building blocks: 1. Stateful Object 2. Process All the other elements are relations between things, expressed graphically as links Prof. Dov Dori 20

21 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 Prof. Dov Dori 21

22 Transform? What does that mean? Transforming means creating an object or destroying an object or affecting an object. 2/8/

23 Transforming an object by a process can be done in three ways (1) Process consumes the object Prof. Dov Dori 23

24 (2) Process creates the object Prof. Dov Dori 24

25 Affecting? What does that mean? A process affects an object by changing its state. Hence, objects must be stateful they must have states. 2/8/

26 The third and last kind of object transformation: (3) Process changes object state: Prof. Dov Dori 26

27 The three transformation kinds Consumption: Creation: State Change: 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 27

28 The graphics-text equivalence OPM principle Any 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) Prof. Dov Dori 28

29 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

30 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 2/8/

31 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? 2/8/

32 The Object-Process Theorem Stateful objects, processes, and relations among them constitute a necessary and sufficient universal ontology. 2/8/

33 Two Complementary Proofs: 1. Theoretical, based on logic 2. Empirical, based on examples 2/8/

34 Theoretical Proof Part 1 - Necessity Stateful 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. 2/8/

35 Theoretical Proof Part 2 - Sufficiency 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. 2/8/

36 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. 2/8/

37 Empirical Proof from Science: Molecular biology 2/8/

38 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. 2/8/

39 Nuclear reactor failure: The Three Mile Island Accident Tripped Pumps Cause too high Pressure Prof. Dov Dori

40 Offshore Oil Well Drilling 2/8/

41 Airport Operations: Outgoing Passenger 2/8/

42 Iron Dome an Israeli ballistic missile defense system Yaniv Mordecai and Dov Dori, Evolving System Modeling: Facilitating Agile System Development with Object-Process Methodology. SysCon 2015,9 th Annual IEEE International Systems Conference, Vancouver, Canada, April To be presented 2/8/

43 Additional sample domains in which OPM has been used Complex, Interconnected, Large-Scale Socio-Technical Systems. Systems Engineering 14(3), Networking Mobile Devices and Computers in an Intelligent Home. International Journal of Smart Home 3(4), pp , October, Multi-Agent Systems. IEEE Transactions on Systems, Man, and Cybernetics Part C: Applications and Reviews, 40 (2) pp , Semantic Web Services Matching and Composition. Web Semantics: Science, Services and Agents on the World Wide Web. 9, pp , Project-Product Lifecycle Management. Systems Engineering, 16 (4), pp , Model-Based Risk-Oriented Robust Systems Design. International Journal of Strategic Engineering Asset Management, 1(4), pp , Medical Robotics and Miscommunication Scenarios. An Object-Process Methodology Conceptual Model. Artificial Intelligence in Medicine, 62(3) pp , Modeling Exceptions in Biomedical Informatics. Journal of Biomedical Informatics 42(4), pp ,

44 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. 44

45 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 Prof. Dov Dori 45

46 In-zooming Out-zooming Example Process Performance Controlling - a metamodel from ISO All the OPDs, at any detail level, are self-similar. They contain only stateful objects, processes, and relations Prof. Dov Dori 46

47 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 Prof. Dov Dori 47

48 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 Prof. Dov Dori

49 Summary: OPM Aspect Unification The 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 49

50 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 Soon freely downloadable as ISO Publically Available Specification Free OPCAT software now downloadable from Prof. Dov Dori

51 OPM Resources: Book: Object-Process Methodology - A Holistic Systems Paradigm, Springer Verlag, Berlin, Heidelberg, New York, Website: Enterprise Systems Modeling Laboratory contains journal & conference papers, free OPCAT software, presentations, projects, and more. 51

52 Join the growing OPM community Here! Questions and (hopefully) Answers Contact: Dov Dori Prof. Dov Dori

53 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 53

54 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 54

55 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) 55

56 Cyber-Physical Gap A cyber-physical gap exists when the state of the informatical object incorrectly indicates the state of the physical object is supposed to represent 56

57 The cyber-physical gap a critical factor in modern systems design It must be accounted for when designing systems, notably safetycritical ones OPM is most suitable for modeling cyber-physical gaps This is due to its notion of essence physical vs. informatical things Prof. Dov Dori

58 Cyber-physical gap example: Three-Mile Island Accident 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! Prof. Dov Dori Full presentation in

59 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 ( ) 130 ( ) Standardization body OMG (2006) ISO (2014) Number of diagram kinds 9 1 Graphic modality yes yes Textual modality no yes Physical-informatical distinction Systemicenvironmental distinction no no yes yes 59