Case studies of ontology interoperation with OBDA and OBDI

A while ago I wrote about tools to access data through an ontology, which had both several positive comments as well as big question marks as to what I was actually talking about. As is not uncommon of DL literature, the theory papers about Ontology-based Data Access (OBDA) and Ontology-based Data Integration (OBDI) are deemed not particularly readable by people who focus more on Semantic Web Technologies and the two demo papers were small examples to show the software to realise OBDA/OBDI works as intended. So, lo and behold, we now have two case studies! And I mean the real stuff, done with operational information systems.

One deals with linking an ontology to a database of a content management system—the National Accessibility Portal for people with disabilities—and doing funky queries, thereby significantly enhancing the web portal’s search capabilities [1] and the other deals with integrating five different data sources through the ontology so as to provide the system engineers of the SELEX-SI company with one coherent view of the information and greatly simplify querying the diverse data sources [2]. The contents of [1] is focused on the user and usage perspectives, whereas [2] has less about that but a 2.5-page summary of the system’s principles and functionality instead; hence, the two papers highlight both different scenarios and different details for ontology interoperation, thereby complementing each other.

The first paper goes into some detail with a methodology, developing an experimental domain ontology (adolena, made in Protégé), efforts to shape it in a way to be more easily usable for OBDA (best to be within a particular “OWL 2 profile”, well, DL-LiteA), using the OBDA Plugin for Protégé to map the classes and properties in the ontology to SQL queries over the database, and with the query interface one can run SPARQL queries. The SPARQL queries can be over the ontology itself, plain queries over the database, or using a combination of reasoning over the ontology and the database. Concerning the latter, when declared with care, you can indeed have a SPARQL query using concepts and roles of the ontology for which there is no data in the database and retrieve the correct answer; page 8 in [1] explains this for the query to retrieve “all devices that assist with upper limb mobility and has the SPARQL equivalent and query answer in a colourful screenshot. At the back-end, it is the DIG-QuOnto server, which is an extension to the original QuOnto reasoner, that does the query unfolding and rewriting; that is, it is a full-fledged reasoner, tailor-made for ontologies that have to deal with lots of data.

An extension to OBDA is OBDI: one first needs the access so as to integrate it. In this case study by the Romans at uni “La Sapienza” and engineers at SELEX-SI [2], they faced the all-too-familiar problem where data (in this case, Configuration and Data Management (C&DM)) was fragmented over various and autonomous sources, managed by different systems under heterogeneous data models, and the data integration was conducted manually. They developed an ontology for the C&DM subject domain, mapped that to the federated “source schema” (i.e., one schema for dealing with the data sources that varied from RDBMS to Excel to HTML), and demonstrate several queries with the Mastro-I solution, which also uses DL-LiteA and its sophisticated reasoner, by using the direct access to the server through the console so as to exploit all its features to the full (GUI improvements are well down in the pipeline by now). One of the major advantages of this OBDI is that you have to declare the mappings only once and then can avail of the comparatively much simpler SPARQL queries, thereby saving both the domain experts and the system engineers a lot of time.

Just in case the experiments did whet your appetite, you would like to know more about it, and discuss it in person (or perhaps, attend the ISWC’08 tutorial that will give an overview of the OBDA/I tools, among other topics): authors of both papers, as well as the theory and tool developers, will be at ISWC 2008 and the co-located OWLED’08 in Karlsruhe (26-30 Oct.).

[1] Keet, C.M., Alberts, R., Gerber, A., Chimamiwa, G. Enhancing web portals with Ontology-Based Data Access: the case study of South Africa’s Accessibility Portal for people with disabilities. Fifth International Workshop OWL: Experiences and Directions (OWLED’08 ). 26-27 Oct. 2008, Karlsruhe, Germany.
Amoroso, A., Esposito, G., Lembo, D., Urbano, P., Vertucci, R.: Ontology-based data integration with MASTRO-I for configuration and data management at SELEX Sistemi Integrati. In: Proc. of SEBD’08. (2008 ) 81-92.

2 responses to “Case studies of ontology interoperation with OBDA and OBDI

  1. Pingback: OWLED’08 in brief « Keet blog

  2. Pingback: OBDA/I Example in the Digital Humanities: food in the Roman Empire | Keet blog

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