Romans Kasperovics

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Finding subgraph isomorphisms is an important problem in many applications which deal with data modeled as graphs. While this problem is NP-hard, in recent years, many algorithms have been proposed to solve it in a reasonable time for real datasets using different join orders, pruning rules, and auxiliary neighborhood information. However, since they have(More)
Initially popularized by Amazon.com, recommendation technologies have become widespread over the past several years, both in the industry and academia. The traditional two-dimensional approach to recommender systems, involving the dimensions of Users and Items, has been subsequently extended to the multidimensional approach supporting additional contextual(More)
The movement in public transport networks is organized according to schedules. The real-world schedules are specified by a set of periodic rules and a number of irregularities from these rules. The irregularities appear as cancelled trips or additional trips on special occasions such as public holidays, strikes, cultural events, etc. Under such conditions,(More)
The Resource Description Framework (RDF) is widely used for sharing biomedical resources, such as the online protein database UniProt or gene database GeneOntology. SPARQL is the native query language for RDF databases and it features regular expressions in queries for which the exact values are either irrelevant or unknown. A recent paper by Lee et al.(More)
The Resource Description Framework (RDF) is widely used for sharing biomedical data, such as gene ontology or the online protein database UniProt. SPARQL is a native query language for RDF, featuring regular expressions in queries for which exact values are either irrelevant or unknown. The use of regular expression indexes in SPARQL query processing(More)
Graphs provide a powerful way to model complex structures such as chemical compounds, proteins, images, and program dependence. The previous practice for experiments in graph indexing techniques is that the author of a newly proposed technique does not implement existing indexes on his own code base, but instead uses the original authors' binary executables(More)
Recurrences are defined as sets of time instants associated with events and they are present in many application domains, including public transport schedules and personal calendars. Because of their large size, recurrences are rarely stored explicitly, but some form of compact representation is used. Multislices are a compact representation that is well(More)
Real-world graph applications are typically domain-specific and model complex business processes in the property graph data model. To implement a domain-specific graph algorithm in the context of such a graph application, simply providing a set of built-in graph algorithms is usually not sufficient nor does it allow algorithm customization to the user's(More)
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