A grounder for SPINdle defeasible logic reasoner

•Proposed a grounder for defeasible logic bottom-up programs focused on stratified theories.•Introduced an algorithm for theory stratification.•The grounder exploits classical backtracking algorithm for instantiation.•Proposed a query optimization technique to achieve an efficient performance in the grounder.•The grounder evaluated by large-scale datasets based on the web data model and behaved efficiently. Defeasible logic (DL) has attracted significant attention in nonmonotonic reasoning and found many applications, particularly in expert systems and knowledge-based systems communities. Even though backward chaining DL reasoners are mature enough to deal with real-life applications by supporting first-order form of the logic, the forward chaining reasoners of this logic programs only adopt propositional form. To address the problem, this paper proposes and evaluates a grounder system for stratified defeasible logic programs specialized for the SPINdle defeasible logic reasoner. Our method combines approaches from dlv and gringo grounders accompanied with a developed indexer and stratification modules for the reasoner. Our experimental results indicate that the system is able to deal with millions of facts generated based on the web data model efficiently. To the best of our knowledge, this system is the first grounder developed for forward chaining DL reasoning approach.