The linked media framework

Schaffert, Sebastian; Bauer, Christoph; Kurz, Thomas; Dorschel, Fabian; Glachs, Dietmar; Fernández, Manuel J.

doi:10.1145/2362499.2362504

Cited by 15 publications

(2 citation statements)

References 5 publications

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“…Moreover, our approach is readily available and has been experimentally evaluated. The comparison with navigational languages for the Web of data (e.g., [14,[48][49][50][51]) is orthogonal to our goal. We also want to mention recent research that studied problems related to SPARQL property paths, including containment and subsumption [52].…”

Section: Other Navigational Languagesmentioning

confidence: 99%

Querying knowledge graphs with extended property paths

Fionda

Pirrò

Consens

2019

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The increasing number of Knowledge Graphs (KGs) available today calls for powerful query languages that can strike a balance between expressiveness and complexity of query evaluation, and that can be easily integrated into existing query processing infrastructures. We present Extended Property Paths (EPPs), a significant enhancement of Property Paths (PPs), the navigational core included in the SPARQL query language. We introduce the EPPs syntax, which allows to capture in a succinct way a larger class of navigational queries than PPs and other navigational extensions of SPARQL, and provide formal semantics. We describe a translation from non-recursive EPPs (nEPPs) into SPARQL queries and provide novel expressiveness results about the capability of SPARQL sub-languages to express navigational queries. We prove that the language of EPPs is more expressive than that of PPs; using EPPs within SPARQL allows to express things that cannot be expressed when only using PPs. We also study the expressiveness of SPARQL with EPPs in terms of reasoning capabilities. We show that SPARQL with EPPs is expressive enough to capture the main RDFS reasoning functionalities and describe how a query can be rewritten into another query enhanced with reasoning capabilities. We complement our contributions with an implementation of EPPs as the SPARQLindependent iEPPs language and an implementation of the translation of nEPPs into SPARQL queries. What sets our approach apart from previous research on querying KGs is the possibility to evaluate both nEPPs and SPARQL with nEPPs queries under the RDFS entailment regime on existing query processors. We report on an experimental evaluation on a variety of real KGs.

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Section: Other Navigational Languagesmentioning

confidence: 99%

Querying knowledge graphs with extended property paths

Fionda

Pirrò

Consens

2019

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“…The first studies how to extend the scope of SPARQL queries to the WWW, with existing work focusing on basic graph patterns [6,16,38] or a more expressive fragment that includes AND, OPT, UNION and FILTER [18]. The second strand of research focuses on emphasizing navigational features, which resulted in new languages such as NautiLOD [10,12], LDPath [33], and LDQL [20].…”

Section: Related Workmentioning

confidence: 99%

SPARQL with property paths on the Web

Hartig

Pirrò

2017

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Abstract. Linked Data on the Web represents an immense source of knowledge suitable to be automatically processed and queried. In this respect, there are different approaches for Linked Data querying that differ on the degree of centralization adopted. On one hand, the SPARQL query language, originally defined for querying single datasets, has been enhanced with features to query federations of datasets; however, this attempt is not sufficient to cope with the distributed nature of data sources available as Linked Data. On the other hand, extensions or variations of SPARQL aim to find trade-offs between centralized and fully distributed querying. The idea is to partially move the computational load from the servers to the clients. Despite the variety and the relative merits of these approaches, as of today, there is no standard language for querying Linked Data on the Web. A specific requirement for such a language to capture the distributed, graph-like nature of Linked Data sources on the Web is a support of graph navigation. Recently, SPARQL has been extended with a navigational feature called property paths (PPs). However, the semantics of SPARQL restricts the scope of navigation via PPs to single RDF graphs. This restriction limits the applicability of PPs for querying distributed Linked Data sources on the Web. To fill this gap, in this paper we provide formal foundations for evaluating PPs on the Web, thus contributing to the definition of a query language for Linked Data. We first introduce a family of reachability-based query semantics for PPs that distinguish between navigation on the Web and navigation at the data level. Thereafter, we consider another, alternative query semantics that couples Web graph navigation and data level navigation; we call it context-based semantics. Given these semantics, we find that for some PP-based SPARQL queries a complete evaluation on the Web is not possible. To study this phenomenon we introduce a notion of Web-safeness of queries, and prove a decidable syntactic property that enables systems to identify queries that are Web-safe. In addition to establishing these formal foundations, we conducted an experimental comparison of the context-based semantics and a reachability-based semantics. Our experiments show that when evaluating a PP-based query under the context-based semantics one experiences a significantly smaller number of dereferencing operations, but the computed query result may contain less solutions.

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Link Traversal Query Processing Over Decentralized Environments with Structural Assumptions

Taelman,

Verborgh

2023

Lecture Notes in Computer Science

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The linked media framework

Cited by 15 publications

References 5 publications

Querying knowledge graphs with extended property paths

Querying knowledge graphs with extended property paths

SPARQL with property paths on the Web

Link Traversal Query Processing Over Decentralized Environments with Structural Assumptions

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