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From Validating Models to Validating Systems

Peter Denno2013-02-25

University of Maryland ISR Colloquium

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Outline

• Introduction / Scoping• Requirements for MBSE• Exchange Form Validation• NIST Work

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Goals

• Describe a “design philosophy” for systems that assist in systems engineering– Framework for linking multiple viewpoints– Framework for research

• Link the design philosophy to NIST workin exchange form validation, requirements engineering, supply chain logistics simulation

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What is special about V&V ? (1)

• IBM Watson- New techniques – exceed human capability in

knowledge-intensive tasks

- “Machine understanding is not human understanding.”

- “Knowledge is not the destination.”

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What is special about V&V ? (2)

• Validation & Verification- Knowledge is the destination. – knowledge, or at least

credible rationale.

• Requirement:- Minimally: be able to explain how the design space was

characterized and demonstrate that requirements are being met.

- Ideally: Provide deductive arguments where appropriate- Show how certain alternatives are indeed incompatible- Reference principles of operation, functions

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Outline

• Introduction / Scoping• Requirements for MBSE• Exchange Form Validation• NIST Work

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Basis for SE decision making

• SE decision making macro level:– Trade studies, simulations, risk assessment, etc.

• SE decision making micro level:– A web (conceptual schema) of information• Uncertain • Conflicting• Isolated

• Uncertainty is quantified• Conflicts resolved• Inter-relation revealed

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Strategy for the micro-level information

• Characterize elements of rationale for SE decision making.

• Each research project touches on only a few of these elements– No single overarching system design intended

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9 Elements of Rationale (1)• Measurement Conditions

– Confidence in the process or environment under which it was measured– “Capacitance was measured using the AC impedance technique.”

• Logical Consistency– Confidence due to consistency with theory. Type consistent.– “P = .05, as we’d expect from the law on conservation of energy.”

• Associativity Across Views– Individuals: knowledge that two references made from different viewpoints refer to

the same thing– “The region P on the CAD model corresponds to these elements

in the FEA mesh.” (Individuals)– Concepts: knowledge that two conceptualizations can be used for the same purpose.– “What the supplier is calling ‘rated maximum pressure’ is what we call ‘rated pressure.”

(Concepts)

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9 Elements of Rationale (2)• Change process

– Knowledge of precursors and the history of properties that distinguish them.

– “The value of P that we calculated for this design is close to what we found in earlier models.”

• Authority– The power that information has due to an approval that is granted or

an estimate of its maturity– “Supplier-provided data also suggest P=.05 is obtainable.”

• Origin in Requirements*– Belief that a requirement is sensitive to it– “Our ability to achieve requirement x diminishes as P exceeds 0.07.”

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9 Elements of Rationale (3)• Origin in organization infrastructure

– Belief because you obtained it in ways consistent with the organization’s best practices.

– “P was obtained from the aero model in the preliminary design library.”

• Consistency with other belief– Belief due to consistency with prevailing contingent facts– “P=0.5 is reasonable in products using component y.”

• V&V Process– Belief that the system in place to manage the other 8 elements is sound

and comprehensive.– “The value of P is confirmed through simulation that is routinely

performed in validation of this product line.”

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9 Elements : Observations

• Coupling and overlap– Authority / Origin in Organizational Infrastructure– Associativity across views / measurement conditions– etc.

• Though these are found in models, they can be expressed from a more comprehensive viewpoint where – Contradictions can be exposed– Cohesion across views can be noted– Trace to requirements is more evident– (These are all parts of V&V)

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MBSE Concepts / Logical View

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Sentence detail / rationale

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Example Usage Patterns

• V & V– Origin in requirements – Automated generation of test cases

• Requirements Engineering– Origin in other belief, emphasis on tracking

contingent facts and engineering change– Refinement

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Outline

• Introduction / Scoping• Requirements for MBSE• Exchange Form Validation• NIST Work

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Exchange Form Validation : Two Methods

1. Axiomatic: How: Map the exchanged content to sentences Identify errors: ex falso quodlibet with a reasoner Advantage: Ontology explains intent Disadvantage: Proofs hard to interpret

2. Metamodel: How: Map the exchanged content to objects Identify errors: Direct structural, with OCL, etc. Advantage: Constraints relate to exchange form Disadvantage: Constraints look like code

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Example use of metamodel

View / Viewpoint: Can be both consistent with a form (a view), and the form by which otherconceptualization are stated (a viewpoint.)

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Example from the UML Metamodel

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Example Specification Constraints

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In MBSE, metamodels play a key role

• Metamodel =(1) a specification of the form a model can take. (well-formedness conditions)

(2) a formalization of the viewpoint that models will express

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Metamodels also play a key role in model exchange

• Metamodel =(1) a specification of the form a model can take. (well-formedness conditions)

Definition of structure serialization

(2) a formalization of the viewpoint that models will express

Illuminate what program structures the elementsof exchange content map to/from.

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Communication with Exchange Standards

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Outline

• Introduction / Scoping• Requirements for MBSE• Exchange Form Validation• NIST Work– Model Interchange Working Group– Supply Chain Logistics Simulation– Collaborative Requirements Engineering

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Outline

• Introduction / Scoping• Requirements for MBSE• Exchange Form Validation• NIST Work– Model Interchange Working Group– Supply Chain Logistics Simulation– Collaborative Requirements Engineering

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OMG Model Interchange Working Group

• Goal: Improve the ability of OMG MOF-based tools (UML, SysML) to exchange information – XMI Serialization – common to MOF-based tools.

• Process– Group: Produce Test Case diagram and reference file– Tool developers: create diagram in their tool, serialize as XMI– Use NIST tool to identify errors (in files and metamodels)– Correct tools and specifications

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NIST UML / SysML Validator

Enter below a file to upload:

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NIST UML / SysML Validator

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NIST UML / SysML Validator

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NIST UML / SysML Validator

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MIWG Results• Stakeholders witness significant improvement

in interoperability

Elaasar & Labiche, 2012

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Outline

• Introduction / Scoping• Requirements for MBSE• Exchange Form Validation• NIST Work– Model Interchange Working Group– Supply Chain Logistics Simulation– Collaborative Requirements Engineering

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Supply Chain Logistics Simulation

• Goal: Demonstrate integrated use of models toward enterprise goals

• Design: Map models, guided by metamodels into sentences that guide compilation of a discrete event simulation.

• Models– UML of ordering / logistics objects– QVT-r mapping of messages to orders– BPMN “stereotyped” + OCL of business decisions– Discrete Event Simulation

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Round Trip Engineering of Supply Chain Logistics

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Logistics Processes (1)

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Logistics Processes (2)

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Business Rule

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Simulation Results

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Outline

• Introduction / Scoping• Requirements for MBSE• Exchange Form Validation• NIST Work– Model Interchange Working Group– Supply Chain Logistics Simulation– Collaborative Requirements Engineering

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Collaborative Requirements Engineering

• Goal: Demonstrate Engineering from Product Data Sheets

• Design: Map product data sheets in to sentences about requirements. Use these to guide engineering simulation and reasoning about alternative designs

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Conclusions

• Continuing roles for deductive reasoning in the automation of SE processes – The nature of V&V, requirements engineering, the

way we think when we engineer, require it.

• Preparing and interpreting macro-level SE decision processes is aided by the integration of multi-viewpoint, micro-level information.

• Metamodels facilitate this integration.

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References• Welty, C; Inside the mind of Watson, 2nd ESWC Summer School, Kalamaki,

2012, http://videolectures.net/eswc2012_welty_watson

• Denno, P; Thurman, T, Mettenburg, J; Hardy, D; On enabling a model-based systems engineering discipline – 18th INCOSE International Symposium (2008)

• Denno, P; Harrison, T; Using Legacy Modeling Artifacts in Supply Chain Logistics Simulation (in draft, 2013)

• ISO 15288 (2008) – Systems and software engineering – System life cycle processes. (2008)