Overview

The Contextualized Knowledge Repository (CKR) is a knowledge representation and reasoning framework that build on Semantic Web technologies to represent, store, query and reason with contextualized knowledge, i.e. knowledge that holds under specific circumstances or contexts. The CKR addresses an arising needs in the Semantic Web, where as large amounts of Linked Data are published on the Web, it is becoming apparent that the validity of published knowledge is not absolute, but often depends on time, location, topic, and other contextual attributes.

In our recent research, we introduced notions of defeasibility and overridings (justifiable exceptions) in reasoning across contexts: we are currently developing formalizations and reasoning methods for CKRs based on SROIQ-RL (i.e. OWL-RL) and EL_bot and with different types of contextual hierarchies.

CKR features

  • intuitive context representation based on the context-as-a-box principle: contexts are treated as small and inter-related knowledge bases qualified along contextual dimensions such as time, space and topic;
  • context structuring along a broader-narrower hierarchy, automatically induced by the qualification of contexts along dimensions and by the structuring of dimensional values;
  • cross-context statements to relate knowledge in different contexts, based on ‘qualified symbols’;
  • contextual reasoning based on OWL 2 RL local reasoning inside contexts and knowledge propagation rules across contexts, with support of ‘CKR closure’ to precompute and materialize all inferrable stetaments;
  • SPARQL-based contextual queries, supporting the constraining and the extraction of knowledge from multiple contexts by extending SPARQL with a CONTEXT keyword;
  • Answer Set Programming based reasoning methods for instance checking and conjunctive query answering for CKRs with defeasible axioms;
  • well defined semantics rooted in established AI principia for contextualized knowledge representation;
  • standard-friendly as rooted in Semantic Web standards as RDF, OWL 2 and Named Graphs.

Implementations

CKR on SPRINGLES

Implementation of CKR defined as SPARQL-based forward rules over multiple RDF named graphs. The framework is implemented over an extension of Sesame called SPRINGLES (SParql-based Rule Inference over Named Graphs Layer Extending Sesame), which supports the specification and execution of inference over Sesame RDF repositories.

Reference paper: DL2013

Related publications: DeRiVe15, EKAW14, ARCOE14

CKRew – CKR datalog rewriter

CKRew provides a datalog translation of OWL2-RL based CKR and supports reasoning with global defeasible axioms (or justifiable exceptions). CKRew is implemented as an extension of the DL to datalog rewriter DReW. and provides a command line utility for the translation of CKRs represented as RDF/TRIG files.
Recently, CKRew has been extended to reason on DL-Lite_R based knowledge bases with defeasible axioms.

Webpage: http://ckrew.fbk.eu/

Reference papers: Artificial Intelligence, KR2018, RuleML+RR19, DL2014

Related publications: CONTEXT19, CILC14, ARCOE13

CKR Prototype

First implementation of the framework, developed in the context of the LiveMemories project. The prototype implements CKR for OWL2-RL/RDFS(S) data on top of the Sesame and OWLIM frameworks, and supports storing, reasoning and querying with contextual knowledge.

Prototype and evaluation page: https://dkm.fbk.eu/technologies/ckr-prototype

Reference papers: K-CAP13, JWS 2012, ESWC12, ESWC10

Related publications: CONTEXT13, DL2012, DL2011, WoMO11, CIAO10, SWAP10

Publications

These publications are related to the development or applications of the CKR framework.

Journal papers:

  • Loris Bozzato, Thomas Eiter, Luciano Serafini: Enhancing context knowledge repositories with justifiable exceptions. Artificial Intelligence 257:72-126, 2018 (paper)
  • Martin Homola, Luciano Serafini Contextualized knowledge repositories for the Semantic Web in Journal of Web Semantics vol. 12, 2012 (paper)

Book chapters:

  • Loris Bozzato, Thomas Eiter, Luciano Serafini: Reasoning with Justifiable Exceptions in EL_bot Contextualized Knowledge Repositories. In Description Logic, Theory Combination, and All That, pp. 110-134, 2019 (paper)

Conference and workshop papers:

  • Loris Bozzato, Christoph G. Schuetz: Towards Distributed Contextualized Knowledge Repositories for Analysis of Large-Scale Knowledge Graphs. In 35mo Convegno Italiano di Logica Computazionale (CILC), 2020 (paper)
  • Loris Bozzato, Thomas Eiter, Luciano Serafini: Justifiable Exceptions in General Contextual Hierarchies. In 11th Int. Conference on Modeling and Using Context (CONTEXT), 2019 (paper)
  • Loris Bozzato, Luciano Serafini, Thomas Eiter: Reasoning with Justifiable Exceptions in Contextual Hierarchies. In 16th International Conference on Principles of Knowledge Representation and Reasoning (KR), 2018 (paper)
  • Loris Bozzato, Luciano Serafini, Gaetano Calabrese: CKR: Live Demo: Using Contexts and Exceptions for Representing Evolving Knowledge States. In 30th Workshop on Description Logics, 2017 (paper)
  • Loris Bozzato, Stefano Borgo, Alessio Palmero Aprosio, Marco Rospocher, Luciano Serafini: A Contextual Framework for Reasoning on Events. in 4th International Workshop on Detection, Representation,and Exploitation of Events in the Semantic Web (DeRiVE), 2015 (paper)
  • Loris Bozzato, Luciano Serafini: Knowledge Propagation in Contextualized Knowledge Repositories: an Experimental Evaluation (extended paper). In 19th International Conference on Knowledge Engineering and Knowledge Management (EKAW), 2014 (paper)
  • Loris Bozzato, Luciano Serafini: Knowledge Propagation in Contextualized Knowledge Repositories: an Experimental Evaluation. In 6th Int. Workshop on Acquisition, Representation and Reasoning with Contextualized Knowledge (ARCOE-LogIC), 2014 (paper)
  • Loris Bozzato, Thomas Eiter, Luciano Serafini: Contextualized Knowledge Repositories with Justifiable Exceptions. In 27th Workshop on Description Logics, 2014 (paper)
  • Loris Bozzato, Thomas Eiter, Luciano Serafini: Defeasibility in contextual reasoning with CKR. In 29mo Convegno Italiano di Logica Computazionale (CILC), 2014 (paper)
  • Loris Bozzato, Martin Homola, Luciano Serafini: ExpTime Tableaux Algorithm for Contextualized ALC. In 8th Int. Conference on Modeling and Using Context (CONTEXT), 2013 (paper)
  • Loris Bozzato, Thomas Eiter, Luciano Serafini: Defeasibility in contextual reasoning with CKR. In 5th Int. Workshop on Acquisition, Representation and Reasoning with Contextualized Knowledge (ARCOE-LogIC), 2013 (notes)
  • Loris Bozzato, Chiara Ghidini, Luciano Serafini: Comparing contextual and flat representations of knowledge – a concrete case about football data. In 7th Int. Conference on Knowledge Capture (K-CAP), 2013 (paper)
  • Loris Bozzato, Luciano Serafini: Materialization Calculus for Contexts in the Semantic Web. In 26th Int. Workshop on Description Logics, 2013 (paper)
  • Loris Bozzato, Martin Homola, Luciano Serafini: Towards More Effective Tableaux Reasoning for CKR. In 25th Workshop on Description Logics, 2012 (paper)
  • Martin Homola, Luciano Serafini: Contextual representation and reasoning with description logics. In 24th Workshop on Description Logics, 2011 (paper)
  • Mathew Joseph, Luciano Serafini: Simple reasoning for contextualized RDF knowledge. In 5th Workshop on Modular Ontologies (WoMo), 2011
  • Martin Homola, Andrei Tamilin, Luciano Serafini: Modeling contextualized knowledge. In 2nd Workshop on Context, Information and Ontologies (CIAO), 2010 (paper)
  • Andrei Tamilin, Bernardo Magnini, Luciano Serafini, Christian Girardi, Mathew Joseph, Roberto Zanoli: Context-Driven Semantic Enrichment of Italian News Archive. In 7th Extended Semantic Web Conference (ESWC), 2010 (paper)
  • Andrei Tamilin, Bernardo Magnini, Luciano Serafini: Leveraging Entity Linking by Contextualized Background Knowledge: A case study for news domain in Italian. In 6th Workshop on Semantic Web Applications and Perspectives (SWAP), 2010 (paper)

Technical reports:

  • Loris Bozzato, Luciano Serafini, Thomas Eiter: Reasoning with Justifiable Exceptions in Contextual Hierarchies (Appendix). CoRR abs/1808.01874, 2018 (report)
  • Loris Bozzato, Martin Homola, Luciano Serafini: ExpTime Reasoning for Contextualized ALC
  • Loris Bozzato, Martin Homola, Luciano Serafini: Evaluation of Contextual Modelling in the FIFA World Cup Use Case (report)
  • Loris Bozzato, Mathew Joseph, Luciano Serafini: Evaluation of contextual queries
  • Martin Homola, Loris Bozzato, Luciano Serafini: Tableaux Algorithm for Reasoning with Contextualized Knowledge

Posters:

  • Loris Bozzato, Luciano Serafini, Gaetano Calabrese: CKR: Live Demo: Representing an Evolving Scenario by Contexts and Exceptions. In International Semantic Web Conference (ISWC) Posters, Demos & Industry Tracks, 2017 (paper)
  • Loris Bozzato, Martin Homola, Mathew Joseph, Luciano Serafini: Managing Contextualized Knowledge with the CKR. In 9th Extended Semantic Web Conference (ESWC), Heraklion, Crete, Greece, 2012 (paper)

Credits

Projects:

  • Initial development of the CKR was supported by the LiveMemories project (Active Digital Memories of Collective Life) aimed at developing methods for automatically interpreting the content of unrelated digital fragments and multimedia data of different nature and provenance, and transforming them into “active memories”.
  • CKR has been lately applied in the Toolisse project for the development of a unified service platform for digital tourism.
  • CKR research has been applied and was supported by the PlanetData European Network of Excellence.
  • Extension of CKR with notion of justifiable exception have been developed in collaboration with the Technical University of Vienna (Prof. Thomas Eiter). Collaboration started within the FBK Mobility Program.
  • CKR framework is currently used in the HumaneAI-Net project in a join micro-project with TU Wien.

CKR Team:

DKMers currently involved: Luciano Serafini, Loris Bozzato

External collaborators: Thomas Eiter (TU Wien)

Past contributors: Mathew Joseph, Martin Homola, Andrei Tamilin, Gaetano Calabrese, Francesco Corcoglioniti

Copyright

Copyright © 2021 the Data & Knowledge Management (DKM) Unit @ Fondazione Bruno Kessler (FBK)

Technology type: Theoretical frameworks

Research topics: Knowledge representation