While incompleteness and uncertainty naturally arises in real-world RDF data, the RDF model itself provides little support for incomplete and uncertain data. In this paper, we introduce practical extensions of the RDF model to represent incompleteness and/or uncertainty. We adopt the semantics of certain answers as the meaningful query answers in the presence of incompleteness and uncertainty, ...

In this paper we introduce RaUL, the RDFa User Interface Language, a user interface markup ontology that is used to describe the structure of a web form as RDF statements. RaUL separates the markup of the control elements on a web form, the form model, from the data model that the form controls operate on. Form controls and the data model are connected via a data binding mechanism. The form ele...

Real scale Semantic Web applications such as Knowledge Portals and E Marketplaces require the management of voluminous repositories of resource metadata The Resource Description Framework RDF enables the creation and exchange of metadata as any other Web data Although large volumes of RDF descriptions are already appearing su ciently expressive declarative query languages for RDF are still miss...

The foundation language for the Semantic Web is the Resource Description Framework (RDF). RDF is intended to describe the Web metadata so that the Web content is not only machine readable but also machine understandable. In this way one can better support the interoperability of Web applications. RDF Schema (RDFS) is used to describe different RDF vocabularies (schemas), i.e., the classes and p...

RDF is the data model of choice for Semantic Web applications. RDF graphs are often large and have heterogeneous, complex structure. Graph summaries are compact structures computed from the input graph; they are typically used to simplify users’ experience and to speed up graph processing. We introduce a formal RDF summarization framework, based on graph quotients and RDF node equivalence; our ...

The RDF data model has recently been extended to support representation and querying of spatial information (i.e., locations and geometries), which is associated with RDF entities. Still, there are limited efforts towards extending RDF stores to efficiently support spatial queries, such as range selections (e.g., find entities within a given range) and spatial joins (e.g., find pairs of entitie...

The Resource Description Framework (RDF) is a graphbased data model promoted by the W3C as the standard for Semantic Web applications. Its associated query language is SPARQL. RDF graphs are often large and varied, produced in a variety of contexts, e.g., scientific applications, social or online media, government data etc. They are heterogeneous, i.e., resources described in an RDF graph may h...

In an Electronic Commerce environment, Semantic Web technologies are promising enablers for large-scale knowledge-based systems, as they facilitate machine-interpretability of data through effective data representation. Fast query engines are required for efficient real-time querying of large amounts of data, usually represented using the Resource Description Framework (RDF). An RDF model is a ...

Recent studies on change detection for RDF data have focused on minimizing the delta size and, as a way to exploit the semantics of RDF models in reducing the delta size, the forward-chaining inferences have been widely employed. However, since the forwardchaining inferences should pre-compute the entire closure of the RDF model, the existing approaches are not scalable to large RDF data sets. ...