Completeness Statements about RDF Data Sources and Their Use for Query Answering

Abstract

With thousands of RDF data sources available on the Web covering disparate and possibly overlapping knowledge domains, the problem of providing high-level descriptions (in the form of metadata) of their content becomes crucial. In this paper we introduce a theoretical framework for describing data sources in terms of their completeness. We show how existing data sources can be described with completeness statements expressed in RDF. We then focus on the problem of the completeness of query answering over plain and RDFS data sources augmented with completeness statements. Finally, we present an extension of the completeness framework for federated data sources.

Enabling Fine-Grained RDF Data Completeness Assessment

“…Note that using the data-agnostic approach from [3], it is not possible to derive the same conclusion. Without looking at the actual graph, we cannot conclude that Ted and Tony are all the crew members of Apollo 99.…”

“…To serialize completeness statements in RDF, we refer the reader to [3]. Now, let us define the semantics of completeness statements.…”

“…Such a check is called completeness entailment. In previous work, Darari et al [3] proposed a framework to describe completeness of RDF data and check query completeness based on completeness information. One fundamental limitation of this work is that the completeness check is agnostic of the content of the RDF data to which the completeness information is given, which results in weaker inferences.…”

Quantifying the Connectivity of a Semantic Warehouse and Understanding Its Evolution Over Time

“…The problem of assessing completeness of Linked Data sources was discussed by Harth and Speiser (2012, July). Darari et al (2013) introduce a formal framework for the declarative specification of completeness statements about RDF data sources and underline how the framework can complement existing initiatives like VoID. They also show how to assess completeness of query answering over plain and RDF/S data sources augmented with completeness statements, and they present an extension of the completeness framework for federated data sources.…”

“…If we would like to associate connectivity with the existing quality dimensions, we could say that it is predominantly interlinking and secondly relevancy and amount-of-data. Of course, it can be exploited together with approaches that focus on completeness (Darari, et al, 2013), provenance (Hartig & Zhao, 2009), accuracy , etc. Regarding relevancy, we should stress that, by construction, a Semantic Warehouse as created by the proposed process (see Figure 2) does not contain irrelevant data since the data has been fetched based on the requirements defined in terms of competency queries.…”