Ioannis Kotsiopoulos

An overview of S-OGSA: A Reference Semantic Grid Architecture

The Grids vision, of sharing diverse resources in a flexible, coordinated and secure manner through dynamic formation and disbanding of virtual communities, strongly depends on metadata. Currently, Grid metadata is generated and used in an ad hoc fashion, much of it buried in the Grid middlewares code libraries and database schemas. This ad hoc expression and use of metadata causes chronic dependency on human intervention during the operation of Grid machinery, leading to systems which are brittle when faced with frequent syntactic changes in resource coordination and sharing protocols. The Semantic Grid is an extension of the Grid in which rich resource metadata is exposed and handled explicitly, and shared and managed via Grid protocols. The layering of an explicit semantic infrastructure over the Grid Infrastructure potentially leads to increased interoperability and greater flexibility. In recent years, several projects have embraced the Semantic Grid vision. However, the Semantic Grid lacks a Reference Architecture or any kind of systematic framework for designing Semantic Grid components or applications. The Open Grid Service Architecture (OGSA) aims to define a core set of capabilities and behaviours for Grid systems. We propose a Reference Architecture that extends OGSA to support the explicit handling of semantics, and defines the associated knowledge services to support a spectrum of service capabilities. Guided by a set of design principles, Semantic-OGSA (S-OGSA) defines a model, the capabilities and the mechanisms for the Semantic Grid. We conclude by highlighting the commonalities and differences that the proposed architecture has with respect to other Grid frameworks.

Using Web service technologies to create an information broker: an experience report

This paper reports on our experiences with using the emerging Web service technologies and tools to create a demonstration information broker system as part of our research into information management in a distributed environment. To provide a realistic context, we chose to study the use of information in the healthcare domain, and this context sets some challenging parameters and constraints for our research and for the demonstration system. In this paper, we both report on the extent to which existing Web service technologies have proved to be mature enough to meet these requirements, and also assess their current limitations.

Enhancing Service Selection by Semantic QoS

The increasing number of functionally similar services requires the existence of a non-functional properties selection process based on the Quality of Service (QoS). Thus, in this article, authors focus on the provision of a QoS model, an architecture and an implementation which enhance the selection process by the annotation of Service Level Agreement (SLA) templates with semantic QoS metrics. This QoS model is composed by a specification for annotating SLA templates files, a QoS conceptual model formed as a QoS ontology and selection algorithm. This approach, which is backward compatible, provides interoperability among customer-providers and a lightweight alternative. Finally, its applicability and benefits are shown by using examples of Infrastructure services.

A Broker Architecture for Integrating Data Using a Web Services Environment

The web service protocol stack provides capabilities for loosely integrating software services but does not provide the higher level support needed for rapid evolution. An experimental system is described for integrating the data from autonomous organizations within the UK health service domain. The results of this experiment have confirmed the need for an integration layer on top of the web service stack to provide the required higher level functionality. In this paper, we summarise our progress to date, and highlight several key research issues of general concern to the web services field, which have emerged from our prototype system. These are set in a general context of providing better ways to provide a service-based model to IT users.

Flexible SLA negotiation using semantic annotations

Moving towards a global market of services requires flexible infrastructures that will deal with the inevitable semantic heterogeneity that occurs during the negotiation that precedes the trading of a service. In order to reach an agreement, the negotiating parties need to understand the concepts describing the Quality of Service (QoS) terms which are part of the Service Level Agreement (SLA). The use of semantic annotations can increase the level of flexibility and automation, allowing the two parties to use their own terminology as long as it is related to the commonly understood conceptual model. This paper discusses how SLA negotiation will benefit from the use of a lightweight backwards compatible semantic annotation mechanism.

Proving the concept of a data broker as an emergent alternative to supra-enterprise EPR systems

Electronic Patient Records systems configured into large enterprise models have become the assumed best route forward. In England, as in several other countries, this has expanded to a major meta-enterprise procurement programme. However, concerns are raised that such systems lack user ownership, and experience from other sectors shows difficulties with large enterprise systems. At a time of great change and once again shifting organizations, is this move simply building large and ponderous edifices with unstable materials? Latest software engineering research is now demonstrating the potential of an alternative model, enabling trusted information brokers to search out in real time at point of use data held in registered local and departmental systems. If successful, this could enable a new and less cumbersome paradigm. The data could move where needed whatever the service configuration. A concept demonstrator has been built set in the context of health and social care in England. It is important for all technological support to the health sector to be reviewed as new technologies emerge so as to identify and exploit new opportunities, and the results of this 3 year project show that the health record information broker route merits further investigative research.

Semantically supported SLA negotiation

The evolution of services market raises the need for automatic support for negotiating service use criteria. In order to reach an agreement, the negotiating parties need to develop a common understanding of the Quality of Service (QoS) terms which are part of the Service Level Agreement (SLA). The use of semantic annotations together with reasoning can increase the level of flexibility and automation in SLA management. A framework is presented for SLA negotiation allowing the two parties to use their own terminologies.

Text-Content-Analysis based on the Syntactic Correlations between Ontologies

The work presented in this chapter is concerned with the analysis of semantic knowledge structures, represented in the form of Ontologies, through which Service Level Agreements (SLAs) are enriched with new semantic data. The objective of the enrichment process is to enable SLA negotiation in a way that is much more convenient for a Service Users. For this purpose the deployment of an SLA-Management-System as well as the development of an analyzing procedure for Ontologies is required. This chapter will refer to the BREIN, the FinGrid and the LarKC projects. The analyzing procedure examines the syntactic correlations of several Ontologies whose focus lies in the field of mechanical engineering. A method of analyzing text and content is developed as part of this procedure. In order to so, we introduce a formalism as well as a method for understanding content. The analysis and methods are integrated to an SLA Management System which enables a Service User to interact with the system as a service by negotiating the user requests and including the semantic knowledge. Through negotiation between Service User and Service Provider the analysis procedure considers the user requests by extending the SLAs with semantic knowledge. Through this the economic use of an SLA-Management-System is increased by the enhancement of SLAs with semantic knowledge structures. The main focus of this chapter is the analyzing procedure, respectively the Text-Content-Analysis, which provides the mentioned semantic knowledge structures.

Architectural patterns for the Semantic Grid

The Semantic Grid reference architecture, S-OGSA, includes semantic provisioning services that are able to produce semantic annotations of Grid resources, and semantically aware Grid services that are able to exploit those annotations in various ways. In this paper we describe the dynamic aspects of S-OGSA by presenting the typical patterns of interaction among these services. A use case for a Grid meta-scheduling service is used to illustrate how the patterns are applied in practice.