An algorithm for compositional nonblocking verification using special events

Abstract

This paper proposes to improve compositional nonblocking verification of discrete event systems through the use of special events. Compositional verification involves abstraction to simplify parts of a system during verification. Normally, this abstraction is based on the set of events not used in the remainder of the system, i. e., in the part of the system not being simplified. Here, it is proposed to exploit more knowledge about the remainder of the system and check how events are being used. Always enabled events, selfloop-only events, failing events, and blocked events are easy to detect and often help with simplification even though they are used in the remainder of the system. Abstraction rules from previous work are generalised, and experimental results demonstrate the applicability of the resulting algorithm to verify several industrial-scale discrete event system models, while achieving better state-space reduction than before.

Programming a fast explicit conflict checker

“…Such models can be difficult to encode as BDDs, causing the BDD algorithm to struggle, while their relatively small state numbers in combination with early termination make them amenable for explicit methods. The models aip1efa16 abs1 and profisafe i4 abs1 are results of compositional minimisation of much larger models [6], which is a potential application of explicit algorithms.…”

“…A lot of effort has been put into the development of algorithms for the automatic verification of this crucial property. Systems of considerable size can be verified using symbolic model checking [2] or compositional verification [3]- [6].…”

“…As all states are stored in memory, they are only suitable for small to medium-size model checking problems with a few million reachable states, which they may solve faster than more complicated algorithms. Compositional verification [3]- [6], which works by simplifying larger models, relies on an explicit or symbolic algorithm in its final step.…”

Supremica–An Efficient Tool for Large-Scale Discrete Event Systems

“…Nbl." refers to compositional nonblocking verification with special events (Pilbrow and Malik, 2015), which is an improved version of the earlier algorithm (Flordal and Malik, 2009). "Mod.…”

“…For a more theoretical description of the modelling framework with extended finitestate machines, the reader may refer to Sköldstam et al (2007) and Mohajerani et al (2016). For more detailed presentations of algorithms, as well as further benchmarks, see for exampleÅkesson et al (2002), Mohajerani et al (2014), and Pilbrow and Malik (2015).…”