Now showing items 1-20 of 40

    • Beyond OWL 2 QL in OBDA: Rewritings and approximations 

      Botoeva E; Calvanese D; Santarelli V; Fabio Savo D; Solimando A; Xiao G (AAAI, 2016)
      Ontology-based data access (OBDA) is a novel paradigm facilitating access to relational data, realized by linking data sources to an ontology by means of declarative mappings. DL-LiteR, which is the logic underpinning the ...
    • Building an FHIR Ontology based Data Access Framework with the OHDSI Data Repositories 

      Jiang G; Xiao G; Kiefer RC; Prod'hommeaux E; Solbrig HR (AIMA, 2017)
    • Cost-Driven Ontology-Based Data Access 

      Lanti D; Xiao G; Calvanese D (Springer, 2017)
      SPARQL query answering in ontology-based data access (OBDA) is carried out by translating into SQL queries over the data source. Standard translation techniques try to transform the user query into a union of conjunctive ...
    • Developing A Semantic Web-based Framework for Executing the Clinical Quality Language Using FHIR 

      Jiang G; Prud’Hommeaux E; Xiao G; Solbrig HR (CEUR-WS.org, 2017)
      The Clinical Quality Language (CQL) is a HL7 specification, aiming to provide a human-readable language to define clinical quality measures and decision support rules while it makes logic expressions independent of any ...
    • Diagnostics of Trains with Semantic Diagnostics Rules 

      Kharlamov E; Savkovic O; Ringsquandl M; Xiao G; Mehdi G; Güzel Kalayci E; Nutt W; Roshchin M; Horrocks I; Runkler T (Springer, 2018)
      Industry today employs rule-based diagnostic systems to minimize the maintenance cost and downtime of equipment. Rules are typically used to process signals from sensors installed in equipment by filtering, aggregating, ...
    • Efficient Handling of SPARQL OPTIONAL for OBDA 

      Xiao G; Kontchakov R; Cogrel B; Calvanese D; Botoeva E (Springer, 2018)
      OPTIONAL is a key feature in SPARQL for dealing with missing information. While this operator is used extensively, it is also known for its complexity, which can make it a challenge to evaluate queries with OPTIONAL ...
    • Efficient Ontology-Based Data Integration with Canonical IRIs 

      Xiao G; Hovland D; Bilidas D; Rezk M; Giese M; Calvanese D (Springer, 2018)
      In this paper, we study how to efficiently integrate multiple relational databases using an ontology-based approach. In ontology-based data integration (OBDI) an ontology provides a coherent view of multiple databases, and ...
    • An Evaluation of VIG with the BSBM Benchmark 

      Lanti D; Xiao G; Calvanese D (CEUR-WS, 2016)
      We present an experimental evaluation of VIG, a data scaler for OBDA benchmarks. Data scaling is a relatively recent approach, proposed in the database community, that allows for scaling an input data instance to s times ...
    • Expressivity and Complexity of MongoDB Queries 

      Botoeva E; Calvanese D; Cogrel B; Xiao G (Schloss Dagstuhl - Leibniz-Zentrum für Informatik, 2018)
      In this paper, we consider MongoDB, a widely adopted but not formally understood database system managing JSON documents and equipped with a powerful query mechanism, called the aggregation framework. We provide a clean ...
    • Fast and Simple Data Scaling for OBDA Benchmarks 

      Lanti D; Xiao G; Calvanese D (CEUR-WS, 2016)
      In this paper we describe VIG, a data scaler for OBDA benchmarks. Data scaling is a relatively recent approach, proposed in the database community, that allows for quickly scaling an input data instance to $n$ times its ...
    • Formalization and Complexity of MongoDB Queries (Extended Abstract) 

      Botoeva E; Calvanese D; Cogrel B; Xiao G (CEUR-WS, 2018)
      In this paper, we study MongoDB, a widely adopted but not formally understood database system managing JSON documents and equipped with a powerful query mechanism, called the aggregation framework.  We define its formal ...
    • Formalizing MongoDB Queries 

      Botoeva E; Calvanese D; Cogrel B; Xiao G (CEUR-WS.org, 2017)
      In this paper, we report on our ongoing work in which we formalize MongoDB, a widely adopted document database system managing complex (tree structured) values represented in a JSON-based data model, equipped with a powerful ...
    • A Generalized Framework for Ontology-based Data Access 

      Botoeva E; Calvanese D; Cogrel B; Corman J; Xiao G (Springer, 2018)
      The database (DB) landscape has been significantly diversified during the last decade, resulting in the emergence of a variety of non-relational (also called NoSQL) DBs, e.g., XML and JSON-document DBs, key-value stores, ...
    • How to Stay Ontop of Your Data: Databases, Ontologies and More 

      Calvanese D; Cogrel B; Komla-Ebri S; Lanti D; Rezk M; Xiao G (Springer, 2015)
      Ontop is an Ontology Based Data Access system allowing users to access a relational database through a conceptual layer provided by an ontology. In this demo, we use the recently developed NPD benchmark (+4~billion triples) ...
    • Inter-organizational Success Factors: A Cause and Effect Model 

      Krathu W; Pichler C; Xiao G; Neidhardt J; Zapletal M; Werthner H; Huemer C (2015)
      Inter-organizational systems form the basis for successful business collaboration in the Internet and B2B e-commerce era. To properly design and manage such systems one needs to understand the structure and dynamics of the ...
    • Metric Temporal Logic for Ontology-Based Data Access over Log Data 

      Calvanese D; Guzel Kalaycı E; Ryzhikov V; Xiao G; Zakharyaschev M (IJCAI Workshop 40, 2016)
      We present a new metric temporal logic HornMTL over dense time and its datalog extension datalogMTL. The use of datalogMTL is demonstrated in the context of ontology-based data access over meteorological data. We show ...
    • The NPD Benchmark for OBDA Systems 

      Lanti D; Rezk M; Slusnys M; Xiao G; Calvanese D (CEUR Electronic Workshop Proceedings, 2014)
      In Ontology-Based Data Access (OBDA), queries are posed over a high-level conceptual view, and then translated into queries over a potentially very large (usually relational) data source. The ontology is connected to the ...
    • The NPD benchmark: Reality check for OBDA systems 

      Lanti D; Rezk M; Xiao G; Calvanese D (OpenProceedings.org, 2015)
      In the last decades we moved from a world in which an enterprise had one central database - rather small for todays' standards - to a world in which many different - and big - databases must interact and operate, providing ...
    • OBDA Beyond Relational DBs: A Study for MongoDB 

      Botoeva E; Calvanese D; Cogrel B; Rezk M; Xiao G (CEUR-WS, 2016)
      The database landscape has been significantly diversified during the last decade, resulting in the emergence of a variety of non-relational (also called NoSQL) databases, e.g., XML and JSON-document databases, key-value ...
    • OBDA Constraints for Effective Query Answering 

      Hovland D; Lanti D; Rezk M; Xiao G (Springer, 2016)
      In Ontology Based Data Access (OBDA) users pose SPARQL queries over an ontology that lies on top of relational data-sources. These queries are translated on-the-fly into SQL queries by OBDA systems. Standard SPARQL-to-SQL ...