06/03/2017 Christos Dimopoulos

New Publication by Dr. Christodoulos Efstathiades

We are pleased to announce that Dr. Christodoulos Efstathiades, member of the Center of Excellence in Risk and Decision Sciences and the Decision Support and Systems Optimisation Laboratory, has a new publication in the journal ‘GeoInformatica‘ :

Hub Labels on the database for large-scale graphs with the COLD framework
Efentakis, A., Efstathiades, C., Pfoser, D., GeoInformatica, pp. 1-30, 2017


Shortest-path computation on graphs is one of the most well-studied problems in algorithmic theory. An aspect that has only recently attracted attention is the use of databases in combination with graph algorithms, so-called distance oracles, to compute shortest-path queries on large graphs. To this purpose, we propose a novel, efficient, pure-SQL framework for answering exact distance queries on large-scale graphs, implemented entirely on an open-source database engine. Our COLD framework (COmpressed Labels on the Database) can answer multiple distance queries (vertex-to-vertex, one-to-many, k-Nearest Neighbors, Reverse k-Nearest Neighbors, Reverse k-Farthest Neighbors and Top-k Range) not handled by previous methods, rendering it a complete database solution for a variety of practical large-scale graph applications. Our experimentation shows that COLD outperforms existing approaches (including popular graph databases) in terms of query time and efficiency, while requiring significantly less storage space than these methods.