157 citations · 244 across the 14 of their papers we have counts for
14 papers
Assessing the Solid Protocol in Relation to Security & Privacy Obligations
Christian Esposito, Olaf Hartig, Ross Horne +1
The Solid specification aims to empower data subjects by giving them direct access control over their data across multiple applications. As governments are manifesting their intere…
LinGBM: A Performance Benchmark for Approaches to Build GraphQL Servers (Extended Version)
Sijin Cheng, Olaf Hartig
GraphQL is a popular new approach to build Web APIs that enable clients to retrieve exactly the data they need. Given the growing number of tools and techniques for building GraphQ…
The Future is Big Graphs! A Community View on Graph Processing Systems
Sherif Sakr, Angela Bonifati, Hannes Voigt +38
Graphs are by nature unifying abstractions that can leverage interconnectedness to represent, explore, predict, and explain real- and digital-world phenomena. Although real users a…
FedQPL: A Language for Logical Query Plans over Heterogeneous Federations of RDF Data Sources (Extended Version)
Sijin Cheng, Olaf Hartig
Federations of RDF data sources provide great potential when queried for answers and insights that cannot be obtained from one data source alone. A challenge for planning the execu…
brTPF: Bindings-Restricted Triple Pattern Fragments (Extended Preprint)
Olaf Hartig, Carlos Buil-Aranda
The Triple Pattern Fragment (TPF) interface is a recent proposal for reducing server load in Web-based approaches to execute SPARQL queries over public RDF datasets. The price for…
Scheduling Refresh Queries for Keeping Results from a SPARQL Endpoint Up-to-Date (Extended Version)
Magnus Knuth, Olaf Hartig, Harald Sack
Many datasets change over time. As a consequence, long-running applications that cache and repeatedly use query results obtained from a SPARQL endpoint may resubmit the queries reg…
Walking without a Map: Optimizing Response Times of Traversal-Based Linked Data Queries (Extended Version)
Olaf Hartig, M. Tamer Özsu
The emergence of Linked Data on the WWW has spawned research interest in an online execution of declarative queries over this data. A particularly interesting approach is traversal…
LDQL: A Query Language for the Web of Linked Data (Extended Version)
Olaf Hartig, Jorge Pérez
The Web of Linked Data is composed of tons of RDF documents interlinked to each other forming a huge repository of distributed semantic data. Effectively querying this distributed…
A Context-Based Semantics for SPARQL Property Paths over the Web (Extended Version)
Olaf Hartig, Giuseppe Pirro
As of today, there exists no standard language for querying Linked Data on the Web, where navigation across distributed data sources is a key feature. A natural candidate seems to…
Reconciliation of RDF* and Property Graphs
Olaf Hartig
Both the notion of Property Graphs (PG) and the Resource Description Framework (RDF) are commonly used models for representing graph-shaped data. While there exist some system-spec…
Foundations of an Alternative Approach to Reification in RDF
Olaf Hartig, Bryan Thompson
This document defines extensions of the RDF data model and of the SPARQL query language that capture an alternative approach to represent statement-level metadata. While this alter…
SPARQL for a Web of Linked Data: Semantics and Computability (Extended Version)
Olaf Hartig
The World Wide Web currently evolves into a Web of Linked Data where content providers publish and link data as they have done with hypertext for the last 20 years. While the decla…
Towards a Query Language for the Web of Data (A Vision Paper)
Juan Sequeda, Olaf Hartig
Research on querying the Web of Data is still in its infancy. In this paper, we provide an initial set of general features that we envision should be considered in order to define…
Foundations of Traversal Based Query Execution over Linked Data (Extended Version)
Olaf Hartig, Johann-Christoph Freytag
Query execution over the Web of Linked Data has attracted much attention recently. A particularly interesting approach is link traversal based query execution which proposes to int…