LODeX: Schema Summarization and automatic SPARQL query generation for Linked Open Data sources
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The document describes LODeX, a system that automatically extracts and summarizes schemas from Linked Open Data sources to help users discover and query these datasets. It extracts statistical indexes from the datasets and uses them to generate interactive schema summaries describing classes, properties, and attributes. Users can then build basic queries through a GUI, which are compiled into SPARQL and executed. The system was tested on over 500 datasets and evaluations found the schema summaries and query generation were over 88% accurate. Future work includes improving the interface based on user surveys and extending the system to cluster summaries for large datasets.
![DBGroup@UNIMO
8
Dot. Fabio Benedetti
Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia
D Day 2015 – Modena Italy
LODeX: Schema Summarization and automatic SPARQL query
generation for Linked Open Data sources
Dot. Fabio Benedetti
Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia 8
Statistical Indexes
They are composed by 9 indexes divided in three groups:
• General group
• Intensional group
• Extensional group
The IE process is able to generate the SPARQL queries used to extract the
different indexes.
• Iterative algorithm able to extract the Intensional knowledge
• Pattern Strategy technique
– It is a technique able to produce an higher number of less complex
SPARQL query
The IE process is able to perform online index extraction handling the
performance issues of the SPARQL endpoints
[F. Benedetti, S. Bergamaschi, and L. Po, “Online index extraction from linked open data sources,” 2014, Linked Data for Information
Extraction (LD4IE) Workshop held at International Semantic Web Conference]](https://image.slidesharecdn.com/20150112dday2015fabio-150112071339-conversion-gate01/85/LODeX-Schema-Summarization-and-automatic-SPARQL-query-generation-for-Linked-Open-Data-sources-7-320.jpg)
![DBGroup@UNIMO
9
Dot. Fabio Benedetti
Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia
D Day 2015 – Modena Italy
LODeX: Schema Summarization and automatic SPARQL query
generation for Linked Open Data sources
Dot. Fabio Benedetti
Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia 9
The elements composing the Schema Summary are:
• Classes
• Properties
• Attributes
An algorithm combines
the information
contained in the
Statistical Indexes to
produce and store the
Schema Summary
[F. Benedetti, S. Bergamaschi, and L. Po, “A visual summary for linked open data sources,” 2014, International
Semantic Web Conference (Posters & Demos)]](https://image.slidesharecdn.com/20150112dday2015fabio-150112071339-conversion-gate01/85/LODeX-Schema-Summarization-and-automatic-SPARQL-query-generation-for-Linked-Open-Data-sources-8-320.jpg)
![DBGroup@UNIMO
12
Dot. Fabio Benedetti
Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia
D Day 2015 – Modena Italy
LODeX: Schema Summarization and automatic SPARQL query
generation for Linked Open Data sources
Dot. Fabio Benedetti
Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia 12
Try LODeX demo at: http://dbgroup.unimo.it/lodex2
[F. Benedetti, S. Bergamaschi, and L. Po, “Visual Querying LOD sources with LODeX,” 2014, submitted at The
Semantic Web journal]](https://image.slidesharecdn.com/20150112dday2015fabio-150112071339-conversion-gate01/85/LODeX-Schema-Summarization-and-automatic-SPARQL-query-generation-for-Linked-Open-Data-sources-11-320.jpg)
LODeX: Schema Summarization and automatic SPARQL query generation for Linked Open Data sources
- 1. DBGroup@UNIMO Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia 1 D Day 2015 – Modena Italy LODeX: Schema Summarization and automatic SPARQL query generation for Linked Open Data sources Fabio Benedetti Department of Engineering “Enzo Ferrari” University of Modena & Reggio Emilia D-Day 2015 - Modena
- 2. DBGroup@UNIMO 3 Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia D Day 2015 – Modena Italy LODeX: Schema Summarization and automatic SPARQL query generation for Linked Open Data sources Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia 3 [Schmachtenberg, Max, Christian Bizer, and Heiko Paulheim. "Adoption of the Linked Data Best Practices in Different Topical Domains." The Semantic Web–ISWC 2014. Springer International Publishing, 2014. 245-260}
- 3. DBGroup@UNIMO 4 Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia D Day 2015 – Modena Italy LODeX: Schema Summarization and automatic SPARQL query generation for Linked Open Data sources Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia 4 *Only 570 datasets belong to the LOD cloud, the remaining datasets do not contain ingoing/outgoing links to the LOD Cloud. 2009 2014* Domain Number % Number % Cross-domain 41 13.95% 41 4.04% Geographic 31 10.54% 21 2.07% Government 49 16.67% 183 18.05% Life sciences 41 13.95% 83 8.19% Media 25 8.50% 22 2.17% Publications 87 29.59% 96 9.47% Social web 0 0.00% 520 51.28% User-generated content 20 6.80% 48 4.73% Total 294 1014 2009 Domain Cross-domain Geographic Government Life sciences Media Publications Social web 2014
- 4. DBGroup@UNIMO 5 Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia D Day 2015 – Modena Italy LODeX: Schema Summarization and automatic SPARQL query generation for Linked Open Data sources Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia 5 The Open Access trends encourage the publication of Open Data in form of Linked Data But discovering LOD sources of interest is a complex task for a user Main issues • Do not exist any standard to document a Dataset • The structure of the Dataset can be understood only manually exploring the Dataset • The Semantic Web technologies are extremely complex for unskilled user
- 5. DBGroup@UNIMO 6 Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia D Day 2015 – Modena Italy LODeX: Schema Summarization and automatic SPARQL query generation for Linked Open Data sources Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia 6 • To automatically extract and summarize a schema (Schema Summary) able to describe a LOD Dataset • Use the Schema Summary to support the user in the information extraction task Online & Automatic extraction • It does not require any additional information by the user • It works with SPARQL endpoints – We have to handle the bad performance issues of these Datasets The Schema Summary has to describe a Dataset • Ontology/Vocabulary (OWL & RDFS constraints) • Open Data (i.e. generated from existing RDBMS)
- 6. DBGroup@UNIMO 7 Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia D Day 2015 – Modena Italy LODeX: Schema Summarization and automatic SPARQL query generation for Linked Open Data sources Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia 7 Two main modules • Extraction & Summarization • Visualization & Querying LODeX uses a NoSQL Database as back-end Input URLs of SPARQL endpoints Output Interactive Schema Summary LOD Cloud SPARQL Queries Schema Summary NoSQL LODeX Post- processing Statistical Indexes LODeX Indexes Extraction Query Orchestrator Schema Summary Visualizzation Schema Summary Basic QueryResults Endpoint URLs Sgvizler SPARQL Queries
- 7. DBGroup@UNIMO 8 Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia D Day 2015 – Modena Italy LODeX: Schema Summarization and automatic SPARQL query generation for Linked Open Data sources Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia 8 Statistical Indexes They are composed by 9 indexes divided in three groups: • General group • Intensional group • Extensional group The IE process is able to generate the SPARQL queries used to extract the different indexes. • Iterative algorithm able to extract the Intensional knowledge • Pattern Strategy technique – It is a technique able to produce an higher number of less complex SPARQL query The IE process is able to perform online index extraction handling the performance issues of the SPARQL endpoints [F. Benedetti, S. Bergamaschi, and L. Po, “Online index extraction from linked open data sources,” 2014, Linked Data for Information Extraction (LD4IE) Workshop held at International Semantic Web Conference]
- 8. DBGroup@UNIMO 9 Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia D Day 2015 – Modena Italy LODeX: Schema Summarization and automatic SPARQL query generation for Linked Open Data sources Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia 9 The elements composing the Schema Summary are: • Classes • Properties • Attributes An algorithm combines the information contained in the Statistical Indexes to produce and store the Schema Summary [F. Benedetti, S. Bergamaschi, and L. Po, “A visual summary for linked open data sources,” 2014, International Semantic Web Conference (Posters & Demos)]
- 9. DBGroup@UNIMO 10 Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia D Day 2015 – Modena Italy LODeX: Schema Summarization and automatic SPARQL query generation for Linked Open Data sources Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia 10 Schema Summary SPARQL compiler SPARQL query Basic Query • The User using the Web Application GUI is driven to building a Basic Query • A refinement panel helps the user in refine the Basic Query A SPARQL compiler automatically generates the corresponding SPARQL query Operator supported by the compiler: • AND • Optional • Filter The query is sent to the SPARQL endpoint and the results can be visualized in a tabular, maps or chart view (pie, bar, etc.) • ORDER BY • LIMIT • OFFSET
- 10. DBGroup@UNIMO 11 Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia D Day 2015 – Modena Italy LODeX: Schema Summarization and automatic SPARQL query generation for Linked Open Data sources Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia 11
- 11. DBGroup@UNIMO 12 Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia D Day 2015 – Modena Italy LODeX: Schema Summarization and automatic SPARQL query generation for Linked Open Data sources Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia 12 Try LODeX demo at: http://dbgroup.unimo.it/lodex2 [F. Benedetti, S. Bergamaschi, and L. Po, “Visual Querying LOD sources with LODeX,” 2014, submitted at The Semantic Web journal]
- 12. DBGroup@UNIMO 13 Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia D Day 2015 – Modena Italy LODeX: Schema Summarization and automatic SPARQL query generation for Linked Open Data sources Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia 13 Test Nov. 2014 Dataset URLs 559 Reachable datasets 302 SPARQL 1.1 compatible 206 Extraction completed 185 Task Correct Answers Schema Summary browsing 94% (32/34) Query generation 88% (60/68) Online survey with 17 anonymous users: • 8 Skilled users • 9 Unskilled user The survey is divided in two parts: • Schema Summary browsing clarity • Query generation
- 13. DBGroup@UNIMO 14 Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia D Day 2015 – Modena Italy LODeX: Schema Summarization and automatic SPARQL query generation for Linked Open Data sources Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia 14 • Modify the interface of LODeX according to the results of the online survey • Extends the VOID descriptor vocabulary in order to represent the Statistical Indexes and publish our data as LOD – Build an observatory for the LOD cloud • Define clustering techniques to reduce the size of the Summary for huge dataset
- 14. DBGroup@UNIMO 15 Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia D Day 2015 – Modena Italy LODeX: Schema Summarization and automatic SPARQL query generation for Linked Open Data sources Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia 15 Accepted papers • Beneventano, D., Bergamaschi, S., Sorrentino, S., Vincini, M., Benedetti, F. “Semantic annotation of the CEREALAB database by the AGROVOC linked dataset” (2014) Ecological Informatics journal, . Article in Press. • F. Benedetti, S. Bergamaschi, and L. Po, “Online index extraction from linked open data sources” 2014, Linked Data for Information Extraction (LD4IE) Workshop held at International Semantic Web Conference • F. Benedetti, S. Bergamaschi, and L. Po, “A visual summary for linked open data sources” 2014, International Semantic Web Conference (Posters & Demos) Submitted papers • F. Benedetti, S. Bergamaschi, and L. Po, “Visual Querying LOD sources with LODeX” 2014, submitted at Semantic Web – Interoperability, Usability, Applicability an IOS Press Journal European projects & schools • Web Science Summer School - Southampton University (20-26 July 2014) • RDA Research Data Alliance - RDA Fourth Plenary Meeting 22 - 24 September 2014 in Amsterdam. I won an Early Career Scientist grant and I belong to the Big Data Analytics Interest group. • Keystone - COST Action IC1302. Autumn 2014 MC and WG Meetings “QUERYING THE SEMANTIC WEB” 17-18 October 2014, Riva del Garda, TN.
- 15. DBGroup@UNIMO 16 Dot. Fabio Benedetti Dip. Ing. “Enzo Ferrari” – University of Modena e Reggio Emilia D Day 2015 – Modena Italy LODeX: Schema Summarization and automatic SPARQL query generation for Linked Open Data sources Thanks for your attention!