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Advanced RDF
Published in Giovanni Bartolomeo, Tatiana Kováčiková, Identification and Management of Distributed Data: NGN, Content-Centric Networks and the Web, 2016
Giovanni Bartolomeo, Tatiana Kováčiková
A named graph is not an RDF graph; rather, it is a pair (name– graph). In this pair, the name is a URIRef, whereas the graph is one of the many possible equivalent RDF graphs.* Two RDF graphs that differ only in their blank nodes are considered equivalent RDF graphs; however, they are part of two different named graphs. Christian Bizer, one of the proponents of named graphs, observes that the relationship between a named graph and a corresponding RDF graph is the same occurring between an instance and its class: there might be infinite instances of one single class; similarly there might be infinite, equivalent, individual named graphs corresponding to the same RDF graph but actually differing from each other in their name and, possibly, in their blank nodes (Carroll et al. 2005).
Towards knowledge-based geovisualisation using Semantic Web technologies: a knowledge representation approach coupling ontologies and rules
Published in International Journal of Digital Earth, 2020
The metadata for geospatial datasets is crucial for providing the context for the data. A common practice is to represent geospatial datasets with named graph(s). The named graph is a key concept of Semantic Web architecture, where a collection of RDF statements is organised in a graph with a URI for identification, allowing metadata to be associated with the dataset; the named graphs can also be treated as objects in triples. To this end, the JRC initiated a working group to develop an extension of the DCAT application profile for data portals in Europe (DCAT-AP9), and this extension (GeoDCAT-AP10) is used for describing geospatial datasets in this context. In this study, we use the developed GeoDCAT-AP as the vocabulary for metadata. Therefore, this work is also an investigation of the benefits obtained from these linked data development endeavours, with a particular focus on visualisation.
State-of-the-Art Approaches for Meta-Knowledge Assertion in the Web of Data
Published in IETE Technical Review, 2021
Sangeeta Sen, Mariana Curado Malta, Biswanath Dutta, Animesh Dutta
Semantics: A named graph can be represented by 5-tuple {N, V, U, B, L}, where U is a set of URIrefs; L is a set of literals (both plain and typed); B is a set of “blank” nodes; V = U ∪ B ∪ L is the set of nodes of N; N is a set of pairs forming a partial function from U to V × U × V. Each pair ng = (n, g) ∈ N is a NG in N, and we write n = name(ng) and g = rdfgraph(ng). Thus, for each ng ∈ N rdfgraph(ng) is a RDF graph (a set of triples) which is named name(ng).