structural abstraction for strong fault models diagnosis (dx 2014 bisfai 2015) roni sternmeir...
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AI@BGU
Structural Abstraction for Strong Fault Models Diagnosis (DX 2014 • BISFAI 2015)
Roni Stern Meir Kalech Orel Elimelech
Ben Gurion University of the Negev, IsraelDepartment of Information Systems Engineering
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Outline Introduction to Diagnosis Model-Based Diagnosis
Definition & Motivation Abstraction Literature Review Research Goal
Methodology Evaluation
Results Conclusions Future Work
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Outline Introduction to Diagnosis Model-Based Diagnosis
Definition & Motivation Abstraction Literature Review Research Goal
Methodology Evaluation
Results Conclusions Future Work
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What is a Diagnosis?• Identifying the reason for a problem by examining observed symptoms.
• Determining which part of the system is failing.
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Examples of Diagnosis Domains
http://symptomchecker.isabelhealthcare.com/
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Diagnosis Approaches• Expert Systems.
• Case-Based Reasoning.
• Probabilistic Reasoning.
• Model-Based Diagnosis.
• And more…
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Outline Introduction to Diagnosis Model-Based Diagnosis
Definition & Motivation Abstraction Literature Review Research Goal
Methodology Evaluation
Results Conclusions Future Work
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Model-Based DiagnosisCar System Model A Real Car
[Raymod Reiter. A theory of diagnosis from first principles. 1987].[Johan de Kleer and Brian C. Williams. Diagnosing multiple faults. 1987].
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Abstraction
32 Components
232
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32 Components
232Faulty
Abstract Diagnosis What caused this black
box to fail?
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Abstraction
Input 1
Input 2
Output
Inputs 3 & 4
Input 1
Input 2
Inputs 3 & 4
Output
Abstraction
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Grounding
Faulty
Input 1 = No Fluids
Input 2 = No Fluids
Expected Output = No FluidsObserved Output = Fluids
Inputs 3 & 4 = No Fluids
Pipe 9 is
Faulty
Grounding
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Architecture & Terminology
Original System
Abstract System
Diagnosis Engine
Abstract DiagnosesDiagnoses for the Original System
Find Abstraction Finds
Grounding
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What if we can’t ground an abstract component?
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Ungroundable Abstract Diagnosis
Input = No Fluids
Expected Output = No FluidsObserved Output = Fluids
Pipe 2 Mode: Healthy \ Blocked
Healthy No Fluids
Blocked No Fluids
Pipe 1
Pipe 2
An abstract component of 2 pipes
The grounding process fails
Using abstraction here is not easy
Can’t explain the observed output Faulty
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Literature Review
[Metodi, Stern, Kalech and Codish. Compiling Model-Based Diagnosis to Boolean Satisfaction. 2012]
Past work assumed 2 behavior modes: Healthy \ Faulty
Faulty Any desired behaviorPipe 1
Pipe 2
Abstract diagnoses will always be groundable
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Literature ReviewSome have already tried to diagnose systems with multiple fault modes.
Conflict-Directed with Abstraction• [Feldman, Provan and van Gemund. 2010]
Compilation-Based with Abstraction• [Torta and Torasso. 2013]
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Our goal is to find an efficient way to diagnose when grounding can fail
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Outline Introduction to Diagnosis Model-Based Diagnosis
Definition & Motivation Abstraction Literature Review Research Goal
Methodology Evaluation
Results Conclusions Future Work
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Discard abstract components
that may not be groundable
1. Pessimistic Approach
More components
Harder to diagnose
The grounding process is easier
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Keep all abstract components and take the risk of failing
during the grounding process.
Less components easier to diagnose
The grounding process is harder
2. Optimistic Approaches
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2.1. Weak-Optimistic Approach
2.2. Strong-Optimistic Approach
Grounding
Fail
Succ
ess
Grounding
Are there more abstract diagnoses?
Fail
Succ
ess
No
Yes
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Outline Introduction to Diagnosis Model-Based Diagnosis
Definition & Motivation Abstraction Literature Review Research Goal
Methodology Evaluation
Results Conclusions Future Work
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Evaluation
• Empirical evaluation.
• The approaches were implemented in Prolog.
• External SAT Solver.
• Modified version of the ISCAS-85 benchmark.
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Results• Three systems:
• Diagnosis algorithm: SATbD
• Timeout: 20 seconds
System ID |Comps.| Before
Abstraction
|Comps.| After
Abstraction
c880 383 77
c1355 546 58
c2670 1193 167
X Axis – The ApproachesY Axis - Success Rate of Solved Instances
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Conclusions & Summary
General approach for abstraction in strong-fault models.
Evaluation on a modified version of the ISCAS-85 benchmark.
Abstraction speeds up the diagnosis process.
Mostly the (weak) optimistic approach is the best.
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Schedule & Future Work Find an efficient method to use abstraction in strong-fault models.
Model the approaches to SAT.
Evaluate the approaches (ISCAS-85 benchmark).
Compare our method to Torta and Torasso. 2013, Feldman et al. 2010.
Optimize the approaches.
Find an hybrid approach based on systems pre-process.
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www.orel-e.com
+972 52 4370054
https://il.linkedin.com/in/
orelelimelech
Questions
?