Guest editors: Miquel Centelles (UB) and Daniele Metilli (UCL)
It is now more than 20 years since the World Wide Web Consortium (W3C) launched its vision and program for the Semantic Web, with the goal of providing automatic systems with automatically processable metadata relating to the information that is published on the web. The creation of automatic systems capable of interpreting data semantically, and of generating autonomous processes based on this capability, was seen as a definitive revolution on the internet. After these 20 years, many technologies and standards have been developed within the framework of this program, and made up the already legendary stack or “layer cake” of the Semantic Web, with their ascending and descending relations, but the degree of their adoption has been uneven. As a whole, we can say that the vision of the Semantic Web is still to be fully realized.
Some technologies have become consolidated and have impacted multiple areas of activity and speciality. This is the case for uniform resource identifiers (URIs), certain serialization formats such as JSON-LD (which in many cases has replaced the original XML-based syntaxes), or ontologies linked, for example, to metadata schemas.
Others have become complements to others that have met with more success in the commercial field. This is the case of the RDF data model, which in many implementations of semantically oriented solutions is complemented (or even replaced) by other graph-oriented models, such as property graphs (Neo4J), or in many other cases even by the traditional relational model. Similarly, the SPARQL query language has sometimes been substituted with far less powerful, but more scalable, alternatives, such as GraphQL.
Finally, there is a group of technologies located at the top of the stack which has never been fully standardized, and in some cases have been postponed or simply abandoned.
In legal and other contexts, the implementation of successful languages and technologies has produced examples of coordinated work on an international scale, and of results that have transcended the limits of the laboratory and the beta constant. This is the case, for example, of the European Legislation Identifier (ELI, https://eur-lex.europa.eu/eli-register/about.html) a system of online access to European Union legislation , which is driving the development of critical information services for the citizens of this millennium.
Many national and local libraries, archives, and museums have also transformed or mapped their catalogue and authority data into RDF, working towards the adoption of standard ontologies (CIDOC CRM, FRBRoo, RiC-O) to replace their traditional metadata schemas. This model, and the existence of data sets related to entities, as is the case with Wikidata, has opened up a scenario of infinite possibilities for the enrichment of data sets which presented significant limitations in their original versions.
More broadly, the linked data publishing model has also been successfully developed. This model has been prioritized by the Five Star Scheme for Open Data Publishing and, more recently, by the FAIR Principles for Research Data Management. In its evolution, it has been integrated into an ecosystem for the generation and publication of semantically enriched data such as knowledge graphs, which offer both open and proprietary versions. This second version is the basis for the knowledge graphs that are becoming a key asset in the management of corporate knowledge, and, at the same time, a key tool for training data in machine learning applications and for explaining the results.
Against this background, the journal calls on researchers and project and service managers to publish their work in issue #51, which will show the evolution of technologies and standards of the Semantic Web. It will also give an idea of the current state of the model for publishing linked (open) data and knowledge graphs aimed at providing information services for the general public, and for members of institutions and companies.
· Management, publication and exploitation of linked open data
· Creation and exploitation of knowledge graphs
· Information services based on linked open data and knowledge graphs
· Artificial intelligence and linked open data
· Textual corpora and linked open data
· Textual corpora and knowledge graphs
· Application of bots in linked open data
· Application of bots in knowledge graphs
· Linked open data and diversity of genres
· Graphs of knowledge and diversity of genres
· FAIR and linked open data
· FAIR and knowledge graphs
· Ontologies and linked open data
· Ontologies and knowledge graphs
· Application of ontologies in information services