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## Conjunctive Regular Path Queries in Lightweight Description Logics

Venue: | PROCEEDINGS OF THE TWENTY-THIRD INTERNATIONAL JOINT CONFERENCE ON ARTIFICIAL INTELLIGENCE |

Citations: | 10 - 2 self |

### Citations

1836 |
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Citation Context ... combined complexity lower bounds for CRPQs. As CRPQs generalize CQs, we inherit an NP lower bound from the well-known NP-hardness in combined complexity of CQ answering in relational databases (see (=-=Abiteboul, Hull, & Vianu, 1995-=-)): Proposition 4.4. CRPQ answering is NP-hard in combined complexity for DL-LiteRDFS. For DL-Lite and EL, we show that CRPQ answering is PSpace-hard for combined complexity, in contrast to CQ answeri... |

468 | Tractable Reasoning and Efficient Query Answering in Description Logics: The DL-Lite Family - Calvanese, Giacomo, et al. - 2007 |

450 | Pushing the EL envelope - Baader, Brandt, et al. - 2005 |

347 | Computational Complexity: A Modern Approach - Arora, Barak - 2009 |

206 | R.: Data complexity of query answering in description logics - Calvanese, Giacomo, et al. - 2013 |

192 | M.: The DL-Lite family and relations - Artale, Calvanese, et al. - 2009 |

191 | Graphlog: a visual formalism for real life recursion
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- 1990
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Citation Context ...a generalization of the related problem of querying graph databases which, like DL instance data, are sets of ground facts using only unary and binary predicates, i.e., node- and edge-labeled graphs (=-=Consens & Mendelzon, 1990-=-; Barceló, Libkin, Lin, & Wood, 2012). The relevance of both problems lies in the fact that in many application areas, data can be naturally represented in such form. This applies, in particular, to ... |

104 | Lower bounds for natural proof systems - Kozen - 1977 |

92 | Query containment for conjunctive queries with regular expressions
- Florescu, Levy, et al.
- 1998
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Citation Context ...ese queries is that they allow for controlled form of recursion that is computationally well behaved yet sufficient for expressing reachability queries and the traversal of paths of unbounded length (=-=Florescu, Levy, & Suciu, 1998-=-). In two-way RPQs (2RPQs), the regular expressions may use the arc labels in the backwards direction, which allows for more flexible path navigation. Notably, this comes at no computational cost: ans... |

84 | nSPARQL: A navigational language for RDF. - Pérez, Arenas, et al. - 2010 |

56 | Expressive languages for path queries over graph-structured data. In - Barceló, Hurtado, et al. - 2010 |

51 |
On conjunctive query answering in EL
- Rosati
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Citation Context ...ill require exponential time in the size of the ontology, which is worst-case optimal for these logics. By contrast, for the lightweight DLs of the DL-Lite (Calvanese, De Giacomo, Lembo, Lenzerini, & =-=Rosati, 2007-=-) and EL (Baader, Brandt, & Lutz, 2005) families, which are the languages of choice for ontology-mediated query answering and notably underlie the OWL 2 QL and EL profiles (Motik, Cuenca Grau, Horrock... |

50 | Answering regular path queries in expressive description logics: An automata-theoretic approach
- Calvanese, Eiter, et al.
- 2007
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Citation Context ...t in the paper, and some notation for regular languages. 2.1 Description Logics We first recall the syntax and semantics of description logics, focusing on the lightweight families of logics DL-Lite (=-=Calvanese et al., 2007-=-) and EL (Baader et al., 2005). We also recall the definition of canonical model for these logics. 318 Regular Path Queries in Lightweight Description Logics IQ (2)RPQ data combined data combined DL-L... |

45 | The Complexity of Conjunctive Query Answering in Expressive Description Logics
- Lutz
- 2008
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Citation Context ...sence of ontological constraints (Levy & Rousset, 1996). Moreover, this complexity is not higher than that of other significantly more restricted settings, such as answering plain CQs in the DL ALCI (=-=Lutz, 2008-=-) or positive first-order queries in ALC (Ortiz & Šimkus, 2014). However, hardness for 2ExpTime is nevertheless a prohibitively high complexity for many applications. Even in data complexity, the alg... |

41 |
Complexity measures for regular expressions
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Citation Context ...regular expressions, in that there exists a polynomial translation of regular expressions into equivalent NFAs, while the translation from NFAs to regular expressions may incur an exponential blowup (=-=Ehrenfeucht & Zeiger, 1974-=-). Thus, to ensure that our complexity results hold regardless of the chosen representation, we will prove our complexity lower bounds using the regular expression representation, and for our upper bo... |

23 | Data complexity in the EL family of description logics - Krisnadhi, Lutz - 2007 |

19 | Query rewriting for Horn-SHIQ plus rules - Eiter, Ortiz, et al. - 2012 |

19 | The Limits on Combining Recursive Horn Rules with Description Logics
- Rousset
- 1996
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Citation Context ... an abbreviation for ALCbSelfreg (Calvanese et al., 2009). 316 Regular Path Queries in Lightweight Description Logics ing and query containment undecidable in the presence of ontological constraints (=-=Levy & Rousset, 1996-=-). Moreover, this complexity is not higher than that of other significantly more restricted settings, such as answering plain CQs in the DL ALCI (Lutz, 2008) or positive first-order queries in ALC (Or... |

18 | Query answering in the Horn fragments of the description logics SHOIQ and SROIQ - Ortiz, Rudolph, et al. - 2011 |

17 |
OWL 2 web ontology language: Profiles. W3C Recommendation
- Motik, Grau, et al.
- 2009
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Citation Context ...y Language is a family of languages for specifying ontologies, endorsed as a standard by the W3C. The current version of the standard, called OWL 2 (OWL Working Group, 2009), features three profiles (=-=Motik et al., 2012-=-) or sublanguages that restrict the expressivity in such a way that logical inference over ontologies can be achieved by efficient algorithms. The three profiles provide different modeling capabilitie... |

17 | Owl 2 web ontology language document overview - Group - 2009 |

14 | Relative expressiveness of nested regular expressions, - Barceló, Pérez, et al. - 2012 |

12 | Querying graph databases - Barceló - 2013 |

12 | C.: Data complexity in the EL family of DLs
- Krisnadhi, Lutz
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Citation Context ... is a match pi for q in IK such that pi(~x) = ~a. Proof sketch. It is well known that the canonical model IK can be homomorphically embedded into any model of K (Calvanese et al., 2007; Rosati, 2007; =-=Krisnadhi & Lutz, 2007-=-; Krötzsch & Rudolph, 2007). It follows that whenever query matches are preserved under homomorphisms, the existence of a match in IK implies the existence of a match in every model. This has been of... |

11 | C.: Complexity of Subsumption in the EL Family of Description Logics: Acyclic and Cyclic Tboxes
- Haase, Lutz
- 2008
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Citation Context ...nowledge bases considered in Theorem 6.11 is of practical relevance. Indeed, several important large-scale ELH terminologies, like the medical ontology SNOMED5, are acyclic terminologies (see, e.g., (=-=Haase & Lutz, 2008-=-)), which are guaranteed to have finite canonical models. Moreover, it has been recently argued that real-world DL-LiteR ontologies often yield canonical models of shallow depth (Kikot, Kontchakov, Po... |

10 | XML Path Language (XPath) 2.0. W3C Recommendation. Available at http://www.w3.org/TR/xpath20 - Berglund, Boag, et al. - 2007 |

9 | Nested regular path queries in description logics - Bienvenu, Calvanese, et al. - 2014 |

8 | M.: Reasoning and query answering in description logics - Ortiz, Simkus - 2012 |

7 | Answering expressive path queries over lightweight DL knowledge bases - Bienvenu, Ortiz, et al. - 2012 |

5 | Mantas Simkus. Query answering in the horn fragments of the description logics - Ortiz, Rudolph - 2011 |

5 | Intersection of regular languages and star hierarchy - Bala - 2002 |

4 | OWL 2 profiles: an introduction to lightweight ontology languages,” in Reasoning Web. Semantic Technologies for Advanced Query Answering - Krötzsch - 2012 |

3 | Conjunctive queries for EL with composition of roles - Krötzsch, Rudolph - 2007 |

3 | S.: How to best nest regular path queries - Bourhis, Krötzsch, et al. - 2014 |

3 | Query rewriting over shallow ontologies
- Kikot, Kontchakov, et al.
- 2013
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Citation Context ..., (Haase & Lutz, 2008)), which are guaranteed to have finite canonical models. Moreover, it has been recently argued that real-world DL-LiteR ontologies often yield canonical models of shallow depth (=-=Kikot, Kontchakov, Podolskii, & Zakharyaschev, 2013-=-). 7. Beyond C2RPQs and Lightweight DLs In this section, we discuss some of the implications of our results and give a brief overview of related results for similar settings. 7.1 Extensions of C2RPQs ... |

3 | Ontology based query answering: The story so far - Ortiz - 2013 |

2 | Containment of nested regular expressions
- Reutter
- 2013
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Citation Context ... nesting were proposed as the basic component of the navigational language nSPARQL for RDF (Pérez, Arenas, & Gutierrez, 2010) and they have received some attention in the setting of graph databases (=-=Reutter, 2013-=-; Barceló, Pérez, & Reutter, 2012). Building on the conference version of this work, we recently studied the query answering problem for nested (C)2RPQs in the presence of DL ontologies (Bienvenu, C... |

2 | The complexity of answering conjunctive and navigational queries over OWL 2 EL knowledge bases - Stefanoni, Motik, et al. - 2014 |

1 | Mantas ˇSimkus. Conjunctive Regular Path Queries in Lightweight Description Logics - Bienvenu, Ortiz |

1 | Mantas ˇSimkus, TrungKien Tran, and Guohui Xiao. Query rewriting for Horn-SHIQ plus rules - Eiter, Ortiz - 2012 |

1 | Graph logics with rational relations: The role of word combinatorics - Barceló, Muñoz - 2014 |

1 |
RDF Schema 1.1. W3C Recommendation. Available at http://www.w3.org/TR/rdf-schema
- Brickley, Guha
- 2014
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Citation Context ...l concepts (∃R) on the righthand side. DL-LiteR is the basis for the OWL 2 QL profile, and DL-LiteRDFS corresponds to the fragment of DL-LiteR that is expressible in the RDF Schema ontology language (=-=Brickley & Guha, 2014-=-). In EL, concept inclusions have the form C1 v C2 where C1, C2 are complex concepts constructed according to the following syntax: C := > | A | C u C | ∃r.C where A ∈ NC and r ∈ NR. The DL ELH additi... |

1 | Regular Path Queries in Lightweight Description Logics Calvanese - Giacomo, G, et al. - 1998 |

1 | XPath for DL ontologies - Kostylev, Reutter, et al. - 2015 |

1 | Revisiting the hardness of query answering in expressive description logics - Ortiz, Šimkus - 2014 |