Dimitrios Kourtesis

Semantic-based QoS management in cloud systems

Cloud Computing and Service Oriented Architectures have seen a dramatic increase of the amount of applications, services, management platforms, data, etc. gaining momentum for the necessity of new complex methods and techniques to deal with the vast heterogeneity of data sources or services. In this sense Quality of Service (QoS) seeks for providing an intelligent environment of self-management components based on domain knowledge in which cloud components can be optimized easing the transition to an advanced governance environment. On the other hand, semantics and ontologies have emerged to afford a common and standard data model that eases the interoperability, integration and monitoring of knowledge-based systems. Taking into account the necessity of an interoperable and intelligent system to manage QoS in cloud-based systems and the emerging application of semantics in different domains, this paper reviews the main approaches for semantic-based QoS management as well as the principal methods, techniques and standards for processing and exploiting diverse data providing advanced real-time monitoring services. A semantic-based framework for QoS management is also outlined taking advantage of semantic technologies and distributed datastream processing techniques. Finally a discussion of existing efforts and challenges is also provided to suggest future directions. We review the concept of Quality of Service in Cloud and Service Oriented Computing.We review the use of Semantics in Cloud and Service Oriented Computing.We review the existing techniques to deal with Big Data.We propose a Lambda Architecture based on Semantics and Big Data.We discuss and outline future challenges in semantic-based QoS management.

Combining SAWSDL, OWL-DL and UDDI for semantically enhanced web service discovery

UDDI registries are included as a standard offering within the product suite of any major SOA vendor, serving as the foundation for establishing design-time and run-time SOA governance. Despite the success of the UDDI specification and its rapid uptake by the industry, the capabilities of its offered service discovery facilities are rather limited. The lack of machine-understandable semantics in the technical specifications and classification schemes used for retrieving services, prevent UDDI registries from supporting fully automated and thus truly effective service discovery. This paper presents the implementation of a semantically-enhanced registry that builds on the UDDI specification and augments its service publication and discovery facilities to overcome the aforementioned limitations. The proposed solution combines the use of SAWSDL for creating semantically annotated descriptions of service interfaces and the use of OWL-DL for modelling service capabilities and for performing matchmaking via DL reasoning.

Run-time Verification of Behavioural Conformance for Conversational Web Services

Web services exposing run-time behaviour that deviates from their behavioural specifications represent a major threat to the sustainability of a service-oriented ecosystem. It is therefore critical to verify the behavioural conformance of services during run-time. This paper discusses a novel approach for run-time verification of Web services. It proposes the utilisation of Stream X-machines for constructing formal behavioural specifications of Web services which can be exploited for verifying that a service’s run-time behaviour does not deviate from what is defined in the specification. Our approach allows for checking both the control flow of a Web service and the values of the data in the generated responses. The paper also proposes a classification of Web services and discusses how different types of services can be verified at run-time. Finally, it presents a run-time monitoring and verification architecture and discusses how it can be integrated into different types of service-oriented infrastructures.

Increased reliability in SOA environments through registry-based conformance testing of Web services

Organisations wishing to engage in industrial collaborative networks will typically seek some guarantees concerning the reliability of their prospective partners before committing to cooperation. Evaluating reliability can encompass several aspects, but one of the most crucial things to consider from a cooperation perspective is whether the software systems that support the business processes of some collaborator actually behave as expected. For organisations that rely on a service-oriented computing infrastructure, this amounts to checking whether the functionality of the respective services is conformant to a given behavioural specification. Todays state of the art lacks standardised methods for creating behavioural specifications of Web services, and also lacks tools for automating the process of behavioural conformance checking through testing. This paper presents a concrete method for creating formal specifications of Web service behaviour and utilising them within service registries for automated testing of service implementations in order to verify and certify their conformance.

Discovery and Selection of Certified Web Services Through Registry-Based Testing and Verification

Reliability and trust are fundamental prerequisites for the establishment of functional relationships among peers in a Collaborative Networked Organisation (CNO), especially in the context of Virtual Enterprises where economic benefits can be directly at stake. This paper presents a novel approach towards effective service discovery and selection that is no longer based on informal, ambiguous and potentially unreliable service descriptions, but on formal specifications that can be used to verify and certify the actual Web service implementations. We propose the use of Stream X-machines (SXMs) as a powerful modelling formalism for constructing the behavioural specification of a Web service, for performing verification through the generation of exhaustive test cases, and for performing validation through animation or model checking during service selection.

Web Service Discovery in the FUSION Semantic Registry

The UDDI specification was developed as an attempt to address the key challenge of effective Web service discovery and has become a widely adopted standard. However, the text-based indexing and search mechanism that UDDI registries offer does not suffice for expressing unambiguous and semantically rich representations of service capabilities, and cannot support the logic-based inference capacity required for facilitating automated service matchmaking. This paper provides an overview of the approach put forward in the FUSION project for overcoming this important limitation. Our solution combines SAWSDL-based service descriptions with service capability profiling based on OWL-DL, and automated matchmaking through DL reasoning in a semantically extended UDDI registry.

Cloud application portability: an initial view

Growing interest towards cloud application platforms has resulted in a large number of platform offerings to be already available on the market and new related products to be continuously launched. However, there are a number of challenges that prevent cloud application platforms from becoming widely adopted. One such challenge is application portability. This paper reports on an ongoing effort to explore the area of cloud application portability. We briefly examine the issue of heterogeneity in cloud platforms and highlight specific platform characteristics that may hinder the portability of cloud applications. We present some high level approaches and existing work that attempts to address this challenge. In order to narrow down the area of our exploration we have been carrying out an experiment in cross-platform application development and deployment with four prominent cloud platforms: OpenShift, Google App Engine, Heroku, and Amazon Elastic Beanstalk. We briefly discuss our initial conclusions from this ongoing experimentation.

Leveraging Semantic Web Service Descriptions for Validation by Automated Functional Testing

Recent years have seen the utilisation of Semantic Web Service descriptions for automating a wide range of service-related activities, with a primary focus on service discovery, composition, execution and mediation. An important area which so far has received less attention is service validation, whereby advertised services are proven to conform to required behavioural specifications. This paper proposes a method for validation of service-oriented systems through automated functional testing. The method leverages ontology-based and rule-based descriptions of service inputs, outputs, preconditions and effects (IOPE) for constructing a stateful EFSM specification. The specification is subsequently utilised for functional testing and validation using the proven Stream X-machine (SXM) testing methodology. Complete functional test sets are generated automatically at an abstract level and are then applied to concrete Web services, using test drivers created from the Web service descriptions. The testing method comes with completeness guarantees and provides a strong method for validating the behaviour of Web services.

Addressing self-management in cloud platforms: a semantic sensor web approach

As computing systems evolve and mature, they are also expected to grow in size and complexity. With the continuing paradigm shift towards cloud computing, these systems have already reached the stage where the human effort required to maintain them at an operational level is unsupportable. Therefore, the development of appropriate mechanisms for run-time monitoring and adaptation is essential to prevent cloud platforms from quickly dissolving into a non-reliable environment. In this paper we present our approach to enable cloud application platforms with self-managing capabilities. The approach is based on a novel view of cloud platforms as networks of distributed data sources - sensors. Accordingly, we propose utilising techniques from the Sensor Web research community to address the challenge of monitoring and analysing continuously flowing data within cloud platforms in a timely manner.

Software Co-development in the Era of Cloud Application Platforms and Ecosystems: The Case of CAST

Interest around cloud computing has been growing quite rapidly during the past few years, and the model of cloud computing is evolving into an indispensable component of innovation strategy across the software industry. We are witnessing a paradigm shift that will have a profound impact on software platforms and ecosystems and will give rise to new forms of software co-development. In this paper we make a first attempt to discuss the evolution of the relationship between software co-development, platforms and ecosystems in the era of cloud computing, and the role of cloud application platforms. We present the case of a cloud application platform designed to support advanced forms of software co-development, and to foster the emergence of a novel type of software ecosystem. As demonstrated, cloud application platforms can be designed in a way that facilitates the emergence of new forms of hierarchical cloud-centric software ecosystems.