RSP-QL was developed by the W3C RDF Stream Processing (RSP) community group as a common way to express and query RDF streams. However, RSP-QL does not provide any way of annotating data on the statement level, for example, to express the uncertainty that is often associated with streaming information. Instead, the only way to provide such information has been to use RDF reification, which adds additional complexity to query processing, and is syntactically verbose. In this paper, we define an extension of RSP-QL, called RSP-QL*, that provides an intuitive way for supporting statement-level annotations in RSP. The approach leverages the concepts previously proposed in RDF* and SPARQL*. We illustrate the proposed approach based on a scenario from a research project in e-health. We provide an open-source implementation of the proposal, and compare it to the baseline approach of using RDF reification. The results show that this way of dealing with statement-level annotations offers advantages with respect to both data transfer bandwidth and query execution performance.
RSPQLstar - Enabling Stement-Level Annotations in RDF Streams.pdf
