Semantic Service Oriented Architecture
Applying Semantics to Service Oriented Architectures
Business integration problems have represented a challenge for the last two to three decades but complete and universal solutions have not yet been found. But the latest developments in the area of Semantic Web and Semantic Web Services as well as the emerging efforts towards Service Oriented Architecture (SOA) bring new opportunities and promise better, more dynamic and more suitable solutions for today’s business
By adopting SOA businesses split their overall functionality in discrete (yet meaningful) pieces, loosely coupled, accessible through well defined interfaces, and well suited for peer-to-peer interactions. Each piece of such functionality is offered and consumed as a Web Service. Further more, augmenting SOA approach with semantics guarantees unambiguous Web Service descriptions and explicit meaning associated with the interchanged data. As a consequence, complex collaboration scenarios can be easily built in a dynamic fashion, sustained by concrete solutions to solve heterogeneity issues at the data, process and protocol levels.
Given this context, the aim of this tutorial is to describe how the Service Oriented Architecture can be used in conjunction with Semantic Web Services to enable ad-hoc collaboration scenarios between business partners. We will focus on the semantic solutions towards data heterogeneity (i.e. data mediation), process heterogeneity (i.e. process mediation) and protocol heterogeneity (i.e. the adapter framework). This tutorial is planned to be a more in-depth analyze of the principle introduces by “The Web
Services Modeling Ontology (WSMO)” tutorial presented at the OASIS Symposium
2005 – “The future of XML Vocabularies”.
The Key Points of the Tutorial
The tutorial briefly introduces the main elements of Semantic Web and Semantic Web Services, as are they specified by Web Services Modeling Ontology (WSMO). Ontologies, Web Services, Goals and Mediators are presented from the WSMO perspective in order to give the audience a short overview on the conceptual model we have adopted. After this, we introduce the Web Service Modeling Execution Environment (WSMX) an execution environment that enables dynamic discovery, selection, mediation, invocation and interoperation of Semantic Web Services. We present the main architectural features of this framework as well as the role of semantics and the benefits we gain compared with classical approaches. The main components of the architecture are presented, paying more attention to those components actively involved in heterogeneity solving, namely the adapter framework (protocol mediation), data mediation and process mediation components. The tutorial closes with a demo of the auxiliary tools that are used in creating semantics description, creating ontology alignments and deploying adaptors.
Detailed description of the tutorial
We present a short overview of the main issues that are addressed through this tutorial.
a) Web Service Modeling Ontology (WSMO)
This section of the tutorial introduces the idea and challenges of Semantic Web Services, as the basis of the subsequent sections. It presents briefly the Web Service Modeling Ontology for describing various aspects related to Semantic Web Services. Additionally, a running example is introduced to facilitate a better understanding of the presented notions. This example is used through out the whole tutorial to illustrate the features of the Semantic SOA.
b) Web Service Modeling Execution Environment (WSMX)
The Web Service Modeling Execution Environment represents our approach towards Semantic SOA. Having WSMO as conceptual model, WSMX follows the principle of the Service Oriented Architecture and uses semantic based solutions to provide operations for Web Services, such as: discovery, selection, mediation, and invocation. In this section of the tutorial we introduce the audience to the main components of the framework and their role in WSMX. We continue with a detailed presentation of the components involved in solving heterogeneity issues, namely the adapter framework, data mediation and process mediation components.
c) Adapter Framework WSMX is a semantic environment which implies that everything inside WSMX needs to be semantically described in terms of an ontology. As a consequence all the data processed by WSMX and its component has to be expressed using the Web Service Modeling Language (WSML), which is the language providing a syntax and formal semantics for WSMO. It is the role of the adapter framework to adjust the various formalisms of the messages arriving at the system border. These transformations are mainly syntactic but they can also have a semantic aspect deriving from the differences between that specific formalism and WSML. The tutorial presents at this stage how various adaptors can be deployed/integrated with WSMX and explains the main differences between an adapter and a mediator.
d) Data Mediation
The Data Mediation component in WSMX deals with heterogeneity problems that can appear at the data level. As mentioned above, all messages in WSMX are semantically described in WSML. This means that data to be mediated is described in terms of ontologies, i.e. data consists of ontology instances.
The heterogeneity problems at the data level appear when the requester and the provider of a service use different ontologies to conceptualize their domain. As a consequence, data has to be transformed from terms of one ontology (e.g. requester’s ontology) into
terms of another ontology (e.g. provider’s ontology). Due to the fact that these
transformations are taking place during run-time the whole process has to be completely automatic. The data mediator component in WSMX achieves this by relying on a set of mappings (semantic relationships) between the source and target ontology identified during design-time and stored in a persistent storage. The tutorial discusses this approach in the context of business scenarios, presents various way of representing the ontology mappings and describes a concrete implementation of such a component. e) Process Mediation
Having the protocol (and format) and data heterogeneity problems solved there is still one more issues to be addressed, namely the interaction mismatches. There could be a case where the requester and the provider of a Web Service understand the semantics of data but they have different requirements for the message exchange pattern to be followed. Essentially this means that one of them expects to receive/send messages in a particular order while the other one has a different messages or a different message order that doesn’t match. The role of the process mediator is to retain, postpone, rebuild or create messages that would allow the communication process to continue. The audience will learn about the types of mismatches addressed in this approach, what are the solutions offered and how the architecture of such a mediator looks like.
f) Web Service Modeling Toolkit (WSMT) The Web Service Modeling Toolkit is a collection of tools for Semantic Web Services implemented within IBM’s Eclipse GUI Framework. The tools look at different aspects of Semantic Web Services, from creation of WSMO Ontologies, Goals, Web Services and Mediators, to creation of data mediation mappings to be used at runtime within WSMX and overall management of the WSMX framework itself. Each of the tools within the WSMT will be presented to the audience, focusing on the tools used with the adapter framework and data mediation components.
Relevance of Tutorial for the OASIS Symposium
OASIS shows a high interest in Service Oriented Architectures having five technical committees whose activities are related to this topic. One of these TCs (OASIS Semantic Execution Environment TC) takes WSMO and WSMX as starting points in “developing
guidelines, justifications, and implementation directions for deploying Semantic Web services in SOA”. Our tutorial would be able to give the audience a better perspective of
the current trends both in OASIS and outside world, in academia and industry.
Target Audience, Benefits, and pre-requisites
The tutorial addresses academic as well as industrial researchers and developers that are working with Web technologies in general and have specific interests in Web services, Semantic Web and Service Oriented Architecture.
Attendees will gain a detailed understanding of the potential benefits of Semantic Web Services and Service oriented Architectures. They will be introduced to the overall design
of the WSMX framework, and get to know existing tools and implementations for Semantic Web Services.
Although no specific knowledge is demanded as a pre-requisite for attending the tutorial, basic knowledge of ontologies and Web Services will allow attendees to better understand and follow the tutorial. Presenters
Adrian Mocan is a researcher at Digital Enterprise Research Institute (DERI). His activity is focused on Semantic Web Services, more precisely on Semantic Web Services interoperation. He has participated in several European projects like DIP (Data, Information, and Process Integration with Semantic Web Services -
http://dip.semanticweb.org/) or Knowledge Web
Over the last two years he has been primarily involved in the WSMX working group focusing on ontology-to-ontology mediation tools. Part of this work, he developed a semi-automatic ontology mapping tool for WSMO ontologies, able to provide mapping suggestions based on semantic and syntactic similarities between the components of two ontologies. He is also a voting member of the Oasis Semantic Execution Environment working group.
Adrian obtained her M. S. in Computer Science at Technical University of Cluj-Napoca, Romania, in 2003.
Selected Semantic Web Services Tutorial in:
- OASIS WSMO Tutorial 2005
Mick Kerrigan is a researcher in the Digital Enterprise Research Institute (DERI) located in Leopold-Franz University Innsbruck, Austria. Originally from Dublin, Ireland, Mick holds a B.Sc. from University College Dublin in Computer Science and is currently pursuing his M.Sc. in National University of Ireland Galway. Over the last year he has been primarily involved in the WSMX working group focusing on front-end tools for Semantic Web Services. The primary output of his work has been the Web Services Modeling Toolkit, a collection of tools for Semantic Web Services, focusing on tools for creating and managing WSMO descriptions. Mick Kerrigan is also a contributor to the WSMO and WSML working groups and has been involved in a number of EU funded projects, namely DIP and Knowledge Web. Mick is also a contributor to and the secretary of the OASIS Semantic Execution Environment technical committee (SEE TC).
Selected Semantic Web Services Tutorial in:
- ISWC 2005
Michal Zaremba is a researcher with DERI, working as system architect and developer
in Semantic Web service systems and also leading Semantic Execution Environment
cluster. He is a founding member of the WSMO and WSMX working group and
member of the Semantic Web Services Interest Group (SWSI) and the Semantic Web
Services Architecture Committee (SWSA). Michal is a chair of Semantic Execution
Environment (SEE) TC and has been an observer to several others TC, as well as a
contributor to the open source implementation of the ebXML registry/repository. Over
the last couple of years he has been involved in a number of EU projects such as DIP,
Knowledge Web, SWWS, Moment, Smartisan and others. He is a chief architect and a
leading developer of an open source implementation of the WSMX system,
coordinating international group of developers across Europe to continue progress on
platform development. His current research interests include Semantic Web Services,
eBusiness, Enterprise Application Integration, B2B Integration as well as Business
Process Management. He has published several papers, given numerous presentations
and a couple of tutorials related to Semantic Web Services at academic and industrial
conferences and workshops.
Selected Semantic Web Services Tutorial in:
- OASIS WSMO Tutorial 2005
- AIMSA 2004
- Net Object Days 2004
- ISWC 2004