Linzhang Wang

1
BACH Bounded reAchability Checker for Linear
Hybrid Automata

• Linzhang Wang
• Joint work with Lei Bu, You Li and Xuandong Li
• Department of Computer Science and Technology,
• National Key Laboratory for Novel Software
  Technology,
• Nanjing University

2
Outline

• Preliminary
• BACH
• Path-Oriented Reachability Checker
• Bounded Reachability Checker
• Case Study
• Conclusion

3

• Preliminary
• BACH
• Path-Oriented Reachability Checker
• Bounded Reachability Checker
• Case Study
• Conclusion

4
Preliminary

• Hybrid System
• Systems contain both discrete and
  continuous components
• Practical Examples
• Embedded System Controller
• VLSI circuits
• Linear Hybrid Automata
• Widely studied formal models for hybrid systems

5
State of The Art

• General Reachability

• BMC Reachability

• Technique
• Polyhedral-Computation
• Tool
• HyTech
• PHAVer
• Limitation
• Exponential Complexity

• Technique
• SATLP
• Tool
• HySAT
• MathSAT
• Limitation
• Encoding-gtHuge Formula-gtMemory?

6
Motivation

• Path-oriented Reachability Checking By LP
• Encoding linear complexity
• Solving polynomial complexity
• Depth First Search Enumeration
• Online Checking Only one path in the memory

7

• Preliminary
• BACH
• Path-Oriented Reachability Checker
• Bounded Reachability Checker
• Case Study
• Conclusion

8
BACH

• LHA Reachability
• Java Based Tool
• Linear Programming Solver OR-Objects.
• http//OpsResearch.com/OR-Objects/index.html
  
• Available online
• http//seg.nju.edu.cn/BACH/BACH.html

9
BACH Structure
10
BACH Functionality

• Graphical LHA Editor
• Reachability Checker
• Path-oriented Reachability Checker
• Bounded Reachability Checker

11
Path-Oriented Reachability Check

• Water-Level Monitor

• Path v0ˆv1ˆv2ˆv3ˆv4ˆv1ˆv5
• time sequence representation
• (v0, t0)ˆ(v1, t1)ˆ(v2, t2)ˆ(v3, t3) ˆ(v4,
  t4)ˆ(v1, t5)ˆ(v5, t6) -gt ti 0, t0 0
• location invariant encoding
• y 10 in location v1 -gt yv1in 10,
  yv1out 10, yv1in t1 yv1out ,
• transition guard encoding
• y 10 in transition e1 -gt yv1out 10
• reset action encoding
• y 1 in transition e0 -gt yv1in 1

12
Bounded Reachability Check

• Water-Level Monitor

• Bound 6
• Target v5
• v0ˆv1
• v0ˆv1ˆv2
• v0ˆv1ˆv2ˆv3
• v0ˆv1ˆv2ˆv3ˆv4
• v0ˆv1ˆv2ˆv3ˆv4ˆv1
• v0ˆv1ˆv2ˆv3ˆv4ˆv1ˆv2
• v0ˆv1ˆv2ˆv3ˆv4ˆv1ˆv5
• v0ˆv1ˆv5

Backtracking

• 2015/9/20

• 12

13

• Preliminary
• BACH
• Path-Oriented Reachability Checker
• Bounded Reachability Checker
• Case Study
• Conclusion

14
Case Study

• Water Level Monitor Temperature
  Controller

15
Path-Oriented Reachability Check
16
Bounded Reachability Check

• Scalability
• Performance

17

• Preliminary
• BACH
• Path-Oriented Reachability Checker
• Bounded Reachability Checker
• Case Study
• Conclusion

18
Conclusion

• Convenient Tool
• Graphical LHA Editor
• Reachability Checker
• Path-oriented Reachability Checker
• Bounded Reachability Checker
• Linear Programming Based Verification
• Depth-First-Search Based Traverse
• Good Scalability and Performance

19

• Thanks
• QA