UNIVERSITY OF HERTFORDSHIRE
             COMPUTER SCIENCE RESEARCH COLLOQUIUM

                            presents

     
	     "Deciding FO-rewritability of Regular Languages and 
		 Ontology-mediated Queries in Linear Temporal Logic"
	

                        Dr. Yury Savateev
                   (University of Hertfordshire)

                        6 November 2024 
                        13:00 -14:00 
                          Room C214

                  Everyone is Welcome to Attend
                  Refreshments will be available
				  
				                               

Abstract:

Our concern is the problem of determining the data complexity of answering an ontology-mediated query (OMQ) formulated in linear temporal logic LTL over (Z,<) and deciding whether it is rewritable to an FO(<)-query, possibly with some extra predicates. First, we observe that, in line with the circuit complexity and FO-definability of regular languages, OMQ answering in AC0, ACC0 and NC1 coincides with FO(<,≡)-rewritability using unary predicates x≡0 (mod n), FO(<,MOD)-rewritability, and FO(RPR)-rewritability using relational primitive recursion, respectively. We prove that, similarly to known PSPACE-completeness of recognising FO(<)-definability of regular languages, deciding FO(<,≡)-and FO(<,MOD)-definability is also PSPACE-complete (unless ACC0=NC1). We then use this result to show that deciding FO(<)-, FO(<,≡)- and FO(<,MOD)-rewritability of LTL OMQs is EXPSPACE-complete.



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Hertfordshire Computer Science Research Colloquium
http://cs-colloq.cs.herts.ac.uk