Julio L. Lemos

Areas of Interest

Knowledge Representation and Reasoning, Description Logic, Model Theory, Constraint Satisfaction Problems.

Current project

Motivated by spatio-temporal reasoning, I investigate complexity of query answering in lightweight Description Logics with datatypes (e. g. reals, integers and rationals with linear order) in a non-uniform way; I am particularly interested in the problem in which the query has, in addition to concept, role and attribute assertions, constraints of the form R(x_1,...,x_n) for some n-ary relation symbol R from a relational structure B = (dom(B); R_1, R_2, ...). To obtain a P/coNP dichotomy (for the total preorder on the rational numbers) based on the shape of the constraints in the query, I used results in constraint satisfation problems. I also plan to investigate query answering with built-in functions, aggregates and non-monotonic negation. My main focus is on conditions on the structure of the ontology and of the query under which this can be made efficiently, i. e., in polynomial time.

Here is an old summary of my results. They were presented at KR2016 - Doctoral Consortium. The papers below contain the current results in detail. Here are the slides for my oral presentation at AAAI-2017, main technical track.

Recent papers

J. Lemos, A. Hernich, F. Wolter, Query Answering in DL-Lite with Datatypes: A Non-Uniform Approach, AAAI 2017 (to appear).

J. Lemos, A. Hernich, F. Wolter, Constraint Patterns for Tractable Ontology-Mediated Queries with Datatypes, DL2016.

Previous projects

I also did some work on OWL ontology engineering (predicting Supreme Court decisions), uniformity in legal interpretation and philosophy of logic at the Institute of Mathematics and Statistics, University of Sao Paulo; I was a researcher at one of the labs of the institute, LIAMF. I also did research at the Max Planck Institute in Hamburg, Germany (funded by Brazil-Canada Chamber of Commerce).


Past: COMP109 (Foundations of Computer Science), COMP118 (Logic in Computer Science). Currently (2017): COMP318 (Advanced Web Technologies: the Semantic Web and Ontologies), and COMP118 (Logic in Computer Science).


The University of Liverpool
Department of Computer Science
Liverpool L69 3BX
United Kingdom
Phone: +44 078 4042 --- 
Email: jlemos [at] liverpool [dot] ac [dot] uk
Office: Room 1.09 (Ashton building)

Maintained by Julius Lemos, J.Lemos@csc.liv.ac.ukUpdated 9.9.2016