University of Southampton Research Repository ePrints Soton Copyright © and Moral Rights for this thesis are retained by the author and/or other copyright owners. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge. This thesis cannot be reproduced or quoted extensively from without first obtaining permission in writing from the copyright holder/s. The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the copyright holders. When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given e.g. AUTHOR (year of submission) "Full thesis title", University of Southampton, name of the University School or Department, PhD Thesis, pagination http://eprints.soton.ac.uk UNIVERSITY OF SOUTHAMPTON Faculty of Physical Sciences and Engineering Electronics and Computer Science Web and Internet Science EXPRESS: Resource-Oriented and RESTful Semantic Web Services by Areeb Alowisheq Thesis for the degree of Doctor of Philosophy 17 October 2014 ABSTRACT This thesis investigates an approach that simplifies the development of Semantic Web services (SWS) by removing the need for additional semantic descriptions. The most actively researched approaches to Semantic Web services introduce explicit semantic descriptions of services that are in addition to the existing semantic descriptions of the service domains. This increases their complexity and design overhead. The need for semantically describing the services in such approaches stems from their foundations in service-oriented computing, i.e. the extension of already existing service descriptions. This thesis demonstrates that adopting a resource-oriented approach based on REST will, in contrast to service- oriented approaches, eliminate the need for explicit semantic service descriptions and service vocabularies. This reduces the development efforts while retaining the significant functional capabilities. The approach proposed in this thesis, called EXPRESS (Expressing RESTful Semantic Services), utilises the similarities between REST and the Semantic Web, such as resource realisation, self-describing representations, and uniform interfaces. The semantics of a service is elicited from a resource’s semantic description in the domain ontology and the semantics of the uniform interface, hence eliminating the need for additional semantic descriptions. Moreover, stub- generation is a by-product of the mapping between entities in the domain ontology and resources. EXPRESS was developed to test the feasibility of eliminating explicit service descriptions and service vocabularies or ontologies, to explore the restrictions placed on domain ontologies as a result, to investigate the impact on the semantic quality of the description, and explore the benefits and costs to developers. To achieve this, an online demonstrator that allows users to generate stubs has been developed. In addition, a matchmaking experiment was conducted to show that the descriptions of the services are comparable to OWL-S in terms of their ability to be discovered, while improving the efficiency of discovery. Finally, an expert review was undertaken which provided evidence of EXPRESS’s simplicity and practicality when developing SWS from scratch. Table of Contents Chapter 1: Introduction ...................................................................................................................... 1 1.1 Motivation and Approach ........................................................................................................... 3 1.2 Hypothesis and Research Questions ................................................................................... 5 1.3 Research Methodology ................................................................................................................. 6 1.4 Contributions ..................................................................................................................................... 7 1.5 Thesis Structure ............................................................................................................................... 8 Chapter 2: Background: Web Services, Representational State Transfer and the Semantic Web ...................................................................................................................... 11 2.1 The World Wide Web (WWW) ................................................................................................... 11 2.1.1 Uniform Resource Identifier (URI).................................................................... 12 2.1.2 Hypertext Markup Language (HTML) ............................................................. 12 2.1.3 Hypertext Transfer Protocol (HTTP) ............................................................... 12 2.2 Web Services .................................................................................................................................... 13 2.2.1 The Origins of Web Services ............................................................................... 13 2.2.2 Web Service Standards ............................................................................................ 15 2.2.3 Service-Oriented Architecture ............................................................................ 18 2.3 REST Representational State Transfer (REST) ............................................................. 19 2.3.1 Origins .............................................................................................................................. 19 2.3.2 Resource-Oriented Architecture ........................................................................ 20 2.3.3 REST vs. ROA ................................................................................................................ 22 2.3.4 Comparison to SOA .................................................................................................. 24 2.4 The Semantic Web ........................................................................................................................ 26 2.4.1 Resource Description Framework (RDF) ...................................................... 27 2.4.2 Web Ontology Language (OWL) ......................................................................... 28 2.4.3 SPARQL Protocol and Query Language (SPARQL) ................................... 29 2.5 Linked Data ...................................................................................................................................... 29 2.5.1 Publishing Linked Data .......................................................................................... 30 2.5.2 Linked Data Applications ...................................................................................... 30 2.6 Semantic Web Services .............................................................................................................. 31 2.7 Summary ............................................................................................................................................ 33 Chapter 3: Approaches to Semantic Web Services ......................................................... 35 3.1 Meta-Models in SWS Descriptions ....................................................................................... 36 3.2 Service-Oriented Meta-Model Approaches ..................................................................... 37 3.2.1 SWS Approaches for WSDL Web Services ..................................................... 37 3.2.2 SWS Approaches for RESTful Web Services ................................................ 40 3.3 Resource-Oriented Meta-Model Approaches ................................................................ 42 3.4 A Classification Matrix for SWS Approaches ................................................................ 45 3.5 Comparison of SWS Approaches Capabilities ............................................................. 49 3.6 Adopted Research Methodologies in SWS Approaches ......................................... 54 3.7 Conclusions ...................................................................................................................................... 59 Chapter 4: Scenario Analysis and RO Modelling ............................................................. 61 4.1 Web Service Scenarios ............................................................................................................... 62 4.1.1 Identifying Communities of Interest .............................................................. 62 4.1.2 Selecting the Scenarios .......................................................................................... 63 4.1.3 Scenario example ....................................................................................................... 64 4.2 Scenario analysis .......................................................................................................................... 65 4.2.1 Eliciting requirements............................................................................................. 65 4.2.2 Resource-Oriented Modelling ............................................................................. 65 4.2.3 Outcomes of the Scenario Analysis ................................................................ 68 4.3 SWS Approaches and Interaction Requirements ........................................................ 70 4.4 Conclusions .....................................................................................................................................