Regular Model Checking Upside-Down: An Invariant-Based Approach

Regular model checking is a technique for the verification of infinite-state systems whose configurations can be represented as finite words over a suitable alphabet. It applies to systems whose set of initial configurations is regular, and whose transition relation is captured by a length-preserving transducer. To verify safety properties, regular model checking iteratively computes automata recognizing increasingly larger regular sets of reachable configurations, and checks if they contain unsafe configurations. Since this procedure often does not terminate, acceleration, abstraction, and widening techniques have been developed to compute a regular superset of the reachable configurations. In this paper we develop a complementary procedure. Instead of approaching the set of reachable configurations from below, we start with the set of all configurations and approach it from above. We use that the set of reachable configurations is equal to the intersection of all inductive invariants of the system. Since this intersection is non-regular in general, we introduce b-bounded invariants, defined as those representable by CNF-formulas with at most b clauses. We prove that, for every b ? 0, the intersection of all b-bounded inductive invariants is regular, and we construct an automaton recognizing it. We show that whether this automaton accepts some unsafe configuration is in EXPSPACE for every b ? 0, and PSPACE-complete for b = 1. Finally, we study how large must b be to prove safety properties of a number of benchmarks

A Pattern-based deadlock-freedom analysis strategy for concurrent systems

Local analysis has long been recognised as an effective tool to combat the state-space explosion problem. In this work, we propose a method that systematises the use of local analysis in the verification of deadlock freedom for concurrent and distributed systems. It combines a strategy for system decomposition with the verification of the decomposed subsystems via adherence to behavioural patterns. At the core of our work, we have a number of CSP refinement expressions that allows the user of our method to automatically verify all the behavioural restrictions that we impose. We also propose a prototype tool to support our method. Finally, we demonstrate the practical impact our method can have by analysing how it fares when applied to some examples

The Cowl - v.1 - n.19 - May 08, 1936

The Cowl - student newspaper of Providence College. Volume 1, Number 19 - May 8, 1936. 8 pages

The Cowl - v.37 - n.2 - Apr 28, 1982

The Cowl - student newspaper of Providence College. Volume 37 - No. 2 - April 28, 1982. 12 pages

The Grizzly, September 28, 2006

Anti-Racist Writer and Educator Speaks to Ursinus Community • Spinach Recall and Dining at Ursinus • Smoking Ban Introduced • Images from Annual Fringe Festival • USGA Town Hall Meeting • Shades of Clay Closes • Beyond the Condom: Guide to Safe Sex • Constitution Day: A Review • An Afternoon with Johnny Knoxville and Bam Margera • Watson Fellowship • Opinions: The Core ; New Zack City • Soccer Struggles • Letter to the Editor • NCAA Drug Testinghttps://digitalcommons.ursinus.edu/grizzlynews/1719/thumbnail.jp

Glimmerglass Volume 47 Number 06 (1987)

Official Student Newspaper Issue is 8 pages long

The Western Mistic, September 20, 1940

https://red.mnstate.edu/western-mistic/1283/thumbnail.jp