Knowledge Graph OLAP: A Multidimensional Model and Query Operations for Contextualized Knowledge Graphs

C. Schütz, L. Bozzato, B. Neumayr, M. Schrefl, L. Serafini
Schu21a (2021)
Semantic Web Journal, Vol 12, No. 4, IOS Press, ISSN 1570-0844, DOI: 10.3233/SW-200419, pp. 649-683, 2021.
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Abstract (English)

A knowledge graph (KG) represents real-world entities and their relationships. The represented knowledge is often context-dependent, leading to the construction of contextualized KGs. The multidimensional and hierarchical nature of context invites comparison with the OLAP cube model from multidimensional data analysis. Traditional systems for online analytical processing (OLAP) employ multidimensional models to represent numeric values for further analysis using dedicated query operations. In this paper, along with an adaptation of the OLAP cube model for KGs, we introduce an adaptation of the traditional OLAP query operations for the purposes of performing analysis over KGs. In particular, we decompose the roll-up operation from traditional OLAP into a merge and an abstraction operation. The merge operation corresponds to the selection of knowledge from different contexts whereas abstraction replaces entities with more general entities. The result of such a query is a more abstract, high-level view – a management summary – of the knowledge.

Keywords: Contextualized Knowledge Repository, knowledge graph management system, knowledge graph summarization, Resource Description Framework, ontologies