Handling Qualitative Preferences in SPARQL over Virtual Ontology-Based Data Access

Tracking #: 2895-4109

Marlene Goncalves
David Chaves-Fraga
Oscar Corcho

Responsible editor: 
Guest Editors Web of Data 2020

Submission type: 
Full Paper
With the increase of data volume in heterogeneous datasets that are being published following Open Data initiatives, new operators are necessary to help users to find the subset of data that best satisfies their preference criteria. Quantitative approaches such as top-k queries may not be the most appropriate approaches as they require the user to assign weights that may not be known beforehand to a scoring function. Unlike the quantitative approach, under the qualitative approach, which includes the well-known skyline, preference criteria are more intuitive in certain cases and can be expressed more naturally. In this paper, we address the problem of evaluating SPARQL qualitative preference queries over an Ontology-Based Data Access (OBDA) approach, which provides uniform access over multiple and heterogeneous data sources. Our main contribution is Morph-Skyline++, a framework for processing SPARQL qualitative preferences by directly querying relational databases. Our framework implements a technique that translates SPARQL qualitative preference queries directly into queries that can be evaluated by a relational database management system. We evaluate our approach over different scenarios, reporting the effects of data distribution, data size, and query complexity on the performance of our proposed technique in comparison with state-of-the-art techniques. Obtained results suggest that the execution time can be reduced by up to two orders of magnitude in comparison to current techniques scaling up to larger datasets while identifying precisely the result set.
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Review #1
By Aidan Hogan submitted on 05/Oct/2021
Review Comment:

I thank the authors for the detailed response, and overall I am happy with the changes made by the authors and recommend acceptance.

I will just note some small issues that could be revised for the camera-ready version:

- "and an SPARQL" -> "and a SPARQL"
- "resulting from the application of σ" Is the query really the result of applying σ? Is it not rather given as input?
- "finding an equivalent qualitative preference query Q_0 = (s, ≺) over S" Is this not sufficient for the definition in the sense that the query is equivalent? You could stop the definition here? (Or is the idea to define what equivalence means? It seems that some of the conditions that follow actually describe how the rewriting is made possible rather than the meaning of equivalence.)
- "In addition, Cyganiak [43] has already been probed that" -> "In additional, Cyganiak [43] has already proved that"
- "there is a function µ" Maybe use another letter? µ is used a lot previously as solutions to SPARQL queries, and is used in the next condition.
- "– there is a mapping µ_i" Again I would suggest to use another letter, or even simpler in this case, since µ_i is never referred to again, just say "(term(v), v_0) ∈ M" removing "µ_i =".