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Top1. Introduction
Semantic Web Services (SWS) have been derived by combining Web services and the Semantic Web, which in turn automates the tasks such as, discovery, selection and composition. Several conceptual models of Semantic Web Services were proposed, such as Web Service Modeling Ontology (WSMO (Domingue et al., 2005)) to provides a conceptual framework and a formal language for semantically describing Web services for the automation of discovering, combining and invoking services over the Web, Semantic Markup for Web Services (OWL-S (Martin et al., 2004)) is an ontology of services that provides a high degree of automation to discover, invoke, compose, and monitor Web resources offering particular services by users and software agents, Semantic Annotations for WSDL (SAWSDL (Lausen et al., 2007)) defines mechanisms using which semantic annotations can be added to WSDL components; however they remained incompatible for SOAP (Box et al., 2000) and WSDL (World Wide Web Consortium, 2007) based traditional Web services due to the different expression languages and expressivity used. On the other hand, The Linked Open Data (LOD) (Data, Linked, 2014) has appeared as a new paradigm of Semantic Web to publish and link heterogeneous data including Open Public Data (Bizer et al., 2009; Heath et al., 2011). The Linked Data model provides a universal web space, where heterogeneous data are connected and integrated. Linked Open Data in cloud provides interlinking of Resource Description Framework (RDF), a standard model for data interchange on the Web with other data sources (e.g. DBpedia, PubMed).
RESTful Web services have received significant attention on the Web in comparison with SOAP-based Web services (Erl, 2000). Key features of RESTful web services and SOAP web services are discussed in (Pautasso et al., 2008; Li et al., 2010; Liu, 2013; AlShahwan et al., 2010). The fundamental reason of this paradigm shift is usage of REST by Web 2.0 supporters including Facebook, Flickr and Amazon. They have removed SOAP-based interfaces for ease in use and resource-based model to implement their services (Ly et al., 2012). Moreover, SOAP-based Web services have been developed by targeting the enterprise requirements although they are relatively complex due to the centralized registry mechanism. On the other side, RESTful services are used to develop mashups to provide an integrated user interface by composing multiple Web services and Web data sources (Bakhari & Baker, 2013; Tilahun et al., 2014). From the above, it clearly states that the adoption of RESTful Web services has changed the architectural & semantic aspects of traditional Web services.
As our earlier work (Garg et al., 2016), we have proposed an integrated approach for SOAP-based web services discovery, selection and composition using Semantic Web and QoS Model to automate the tasks to facilitate end user the value-added services with assurance of quality. By applying this principle to RESTful web services, we have planned to develop framework using Linked Data and RDF for semantically described web services. The convergence of RESTful Web services and Linked Data Principles provides the resource and data-oriented discovery, selection and composition with significant level of automation. This solves the issues of manual efforts needed to search and integrate the data resources. Moreover, Linked Data resources and RDF data model also help to maintain the loose coupling between client and service, while the traditional approaches of service composition follows tightly coupled behaviour (Stadmuller, 2012).
Contribution: In our earlier work of RESTful web services (Modi & Garg, n.d.), we have presented framework and approach for service discovery and composition using Lined Data. This work is extended further by incorporating selection approach to propose an efficient integrated framework. As a contribution, we propose an integrated framework and approach for RESTful service discovery, selection and composition using Linked Open Data Principles. This enables a user to discover and integrate services automatically from heterogeneous resources. Our main contribution is summarised as follows: