Linked Services


In a nutshell, Linked Services are services described as Linked Data. Therefore, these are service descriptions whereby their inputs and outputs, their functionality, and their non-functional properties are described in terms of (reused) light weight RDFS vocabularies and exposed following Linked Data principles. […] Secondly, by virtue of these descriptions, Linked Services are therefore services that, with appropriate infrastructure support, can consume RDF from the Web of Data, and, if necessary, can also generate additional RDF to be fed back to the Web of Data. In other words, Linked Services constitute a processing layer on top of the wealth of information currently available in the Web of Data which remains unexploited.

Carlos Pedrinaci and John Domingue.  Toward the Next Wave of Services:
Linked Services for the Web of Data
, Journal of Universal Computer Science, 2010.

The advent of Web services and related technologies was quickly followed by considerable hype and grandiose expectations with respect to the impact Web services would have for enterprises and the economy in general. It was often assumed that Web services would ultimately lead to the creation of a service-based economy over the Web. However, Web services are nowadays mostly used within controlled environments such as large enterprises rather than on the Web. One could argue that a reason for this lack of take up is the fact that Web services, despite their name, were not really thought for the Web [1]. In fact, the considerable complexity of the WS-* stack did hamper their adoption on the Web as recent practice based instead on the use of simpler approaches such as Web APIs shows. Another reason is, however, the fact that Web services have essentially targeted enterprises, which tend not to publicly publish Web services in any significant numbers.

Research on Semantic Web Services (SWS) managed to alleviate some of the technical drawbacks of existing Web services technologies. Despite the advanced results obtained, none of the approaches devised gained widespread adoption for three main reasons. First and foremost, all SWS approaches have built upon Web services technologies that are not prevalent on the Web. Secondly, SWS add complex logics to an already complex WS-* stack. SWS require complex architectures, highly advanced reasoning machinery, and rich semantic annotations that, up until now, had to be provided mostly from scratch by highly trained IT staff. Finally, the existing dichotomy between the syntactic level and the semantic level requires devoting significant effort to providing transformation mechanisms between semantic and syntactic representations of information which add further need for manual labour and are highly sensitive to minor variations on data representation.

The advent of the Web of Data together with the rise of Web 2.0 technologies and social principles probably constitute the final necessary ingredients that could ultimately lead to a widespread adoption of services on the Web. The main reasons for this are the existing technical symbiosis between services, semantics, and the Web of Data [2], as well as the rise of the prosumer and the global movement towards an open Web driven by the current unprecedented sharing of data and functionality openly on the Web.

From a technological perspective, the evolution of the Web of Data is highlighting the fact that light weight semantics yield significant benefits that justify the investment in annotating data and deploying the necessary machinery. This initiative is contributing to generate an outstanding body of knowledge (light weight ontologies and data expressed in their terms) that can help to significantly reduce the effort for creating semantic annotations for services. Furthermore, it also represents a significant use case for the application of services technologies on a Web scale in order to process this wealth of data which remains nowadays largely unexploited.

From a socio-economic stand point, the recent evolution around Web 2.0 has shown that collaboration over the Web can lead to large quantities of very useful data with a low cost. Similarly, both Web 2.0 and more recently Linked Data technologies are encouraging enterprises and institutions to offer their data and services publicly at a previously unprecedented scale and pace. This scenario provides in our view suitable technologies and data, as well as the necessary economic and social interest for the wide application of services technologies on a Web scale.

The vision we are pursuing toward the next wave of services – Linked Services – is based on two simple ideas: publishing service annotations in the Web of Data, and creating services for the Web of Data, i.e., services that process Linked Data and generate Linked Data. In a nutshell, Linked Services are services described as Linked Data. Therefore, these are service descriptions whereby their inputs and outputs, their functionality, and their non-functional properties are described in terms of (reused) light weight RDFS vocabularies and exposed following Linked Data principles. In fact, as such, Linked Services descriptions represent highly valuable information which is still to be provided in the Web of Data: data about reusable functionality on the Web. Secondly, by virtue of these descriptions, Linked Services are therefore services that, with appropriate infrastructure support, can consume RDF from the Web of Data, and, if necessary, can also generate additional RDF to be fed back to the Web of Data. In other words, Linked Services constitute a processing layer on top of the wealth of information currently available in the Web of Data which remains unexploited.

We have taken initial steps in this direction notably through the creation of a set of simple RDFS vocabularies for describing services [3,4,5], and a set of tools for creating service annotations, e.g., SWEET [6], and iServe [5] a Linked Services registry that publishes service annotations as Linked Data and provides advanced discovery functionalities on top of it.

You can read more about Linked Services at [7].

References

[1]  Steve Vinoski. Putting the “Web” into Web Services: Interaction Models, Part 2. IEEE Internet Computing, 6(4):90–92, 2002.

[2] Carlos Pedrinaci, John Domingue, and Reto Krummenacher. Services and the Web of Data: An Unexploited Symbiosis. In Linked AI: AAAI Spring Symposium ”Linked Data Meets Artificial Intelligence”, 2010.

[3] Tomas Vitvar, Jacek Kopecky, Jana Viskova and Dieter Fensel. WSMO-Lite Annotations for Web Services. In M. Hauswirth, M. Koubarakis and S. Bechhofer, editors, Proceedings of the 5th European Semantic Web Conference, LNCS, Berlin, Heidelberg. Springer Verlag, 2008.

[4] Jacek Kopecky, Karthik Gomadam and Tomas Vitvar. hRESTS: an HTML Microformat for Describing RESTful Web Services. In The 2008 IEEE/WIC/ACM International Conference on Web Intelligence (WI2008), Sydney, Australia. IEEE CS Press, 2008

[5] Carlos Pedrinaci, Dong Liu, Maria Maleshkova, Dave Lambert, Jacek Kopecky and John Domingue. iServe: a Linked Services Publishing Platform, Workshop: Ontology Repositories and Editors for the Semantic Web at 7th Extended Semantic Web Conference. 2010.

[6] Maria Maleshkova, Jacek Kopecky and Carlos Pedrinaci.  Adapting SAWSDL for Semantic Annotations of RESTful Services, Workshop: Beyond SAWSDL at OnTheMove Federated Conferences & Workshops, Vilamoura, Portugal, 2009.

[7] Carlos Pedrinaci and John Domingue.  Toward the Next Wave of Services: Linked Services for the Web of Data, Journal of Universal Computer Science, 2010.