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Papers by George Athanasopoulos

Springer eBooks, Mar 8, 2006

Peer-to-peer (p2p) applications exhibit characteristics such as dynamic network topology and conf... more Peer-to-peer (p2p) applications exhibit characteristics such as dynamic network topology and configuration, heterogeneity and scalability that make their development a complicated task. This is further aggravated due to the required satisfaction of dependability properties, i.e. security, availability, reliability, etc. Furthermore, p2p application requirements are driven by the software architecture adopted for their development while in other kinds of applications, the requirements drive the architecture. It is therefore only natural to adopt an architecture-based approach for the development of p2p dependable applications in order to ensure at the architectural level that dependability requirements are met. An essential part for the effective architecture-based development is the use of an appropriate modelling mechanism. In this paper we argue on the use of a UML profile that provides appropriate constructs and notations for modelling dependable p2p software architectures.

Within the currently forming pervasive computing environment services and information sources thr... more Within the currently forming pervasive computing environment services and information sources thrive. Instantiations of the service oriented computing paradigm e.g. Web, Peer-to-Peer (P2P) and Grid services are continuously emerging, whilst information can be collected from several information sources e.g. materialisations of the Web 2.0 and Web 3.0 trends, Social Networking apps and Sensor Networks. Within this context the development of adaptable service oriented processes utilising heterogeneous services, in addition to available information is an emerging trend. This paper presents an approach and an enabling architecture that leverage the provision of data-driven, adaptable, heterogeneous service processes. Core within the proposed architecture is a set of interacting components that accommodate the acquisition of information, the execution of service chains and their adaptation based on collected information. 1 Dissertation Summary Our era has been marked by a shift in the way...

Στο υπό εξέλιξη διαδίκτυο, όπου ανθούν οι υπηρεσίες και οι πηγές πληροφορίας, η παροχή προσαρμοζό... more Στο υπό εξέλιξη διαδίκτυο, όπου ανθούν οι υπηρεσίες και οι πηγές πληροφορίας, η παροχή προσαρμοζόμενων υπηρεσιοστρεφών διαδικασιών οι οποίες εκμεταλλεύονται διαθέσιμες υπηρεσίες και πληροφορίες, αποτελεί επιτακτική ανάγκη και όχι απλά επιθυμητό χαρακτηριστικό. Στόχος των προσαρμοζόμενων διαδικασιών είναι η «χρήση διαθέσιμων πληροφοριών σχετικών με τις αλλαγές του περιβάλλοντος τους με σκοπό την βελτιστοποίηση της συμπεριφοράς τους». Στο σύνολο των τεχνικών που έχουν εφαρμοστεί ως τώρα μπορεί κανείς να αναγνωρίσει διάφορες κατηγορίες, όπως για παράδειγμα, τεχνικές από το χώρο της Τεχνητής Νοημοσύνης, τεχνικές από το χώρο της υπολογιστικής Πλαισίου, ή ακόμη από το χώρο της υπολογιστικής Όψεων. Ομοίως όταν κανείς εξετάζει το κύκλο ζωής διαδικασιών, εάν και η προσαρμογή μιας διαδικασίας είθισται να λαμβάνει χώρα κατά το χρόνο εκτέλεσης, είναι απαραίτητο να λαμβάνεται υπόψη το ‘πότε’ πραγματοποίούνται οι περισσότεροι υπολογισμοι, π.χ. κατά το χρόνο εκτέλεσης, το χρόνο σχεδιασμού ή το χρό...

International Journal of Spatial Data Infrastructures Research, Sep 16, 2010

Serving geographic information via standardized Web services has been widely accepted as a useful... more Serving geographic information via standardized Web services has been widely accepted as a useful approach. Web-enabled environmental models simulating real-world phenomena are, however, rare. The models predict observations traditionally served by geospatial Web services compliant to well-defined standards. Using standardized Web services could support decoupling of models, comparison of similar models, and the automatic integration into existing geospatial workflows. Modeling experts face several open issues when migrating existing environmental computer models to the Web. The selection of the Web service interface depends on the input parameters required for the successful execution of the computer model. Loosing control over the execution of the models, and consequently also the confidence in model results, can be addressed to a certain extent by using translucent and standardized workflow languages. Mechanisms and open problems for the implementation of geospatial Web service compositions are discussed. Two scenarios about oil spills and the exposure to air pollution illustrate the impact of unconfigured model parameters for standard-compliant spatial data clients.

Icsoft, 2006

Our era has been marked by the emergence of the service oriented computing (SOC) paradigm. This n... more Our era has been marked by the emergence of the service oriented computing (SOC) paradigm. This new trend has reshaped the way distributed applications are built and has influenced current computing paradigms, such as p2p and grid computing. SOC's main objective is to leverage interoperability among applications and systems; however, the emergence of various types of services such as web, grid and p2p services has raised several interoperability concerns among these services as well as within each of these service models. In order to surpass these incompatibilities, appropriate middleware and mechanisms need to be developed so as to provide the necessary layers of abstraction and a unified framework that will obscure a service user from the underlying details of each service platform. Yet, for the development of such middleware and mechanisms to be effective, appropriate conceptual models need to be constructed. Within this paper, we briefly present a generic service model which was constructed to facilitate the unified utilization of heterogeneous services, with emphasis on its properties for the modeling of p2p services. Moreover, we illustrate how this model was instantiated for the representation of JXTA services and present the service description and discovery mechanisms that were built upon it. We regard this generic service model as a first step in achieving interoperability between incompatible types of services.

Icsoft, 2010

Within the currently forming pervasive computing environment, services and information sources th... more Within the currently forming pervasive computing environment, services and information sources thrive. Instantiations of the service oriented computing paradigm, e.g. Web, Peer-to-Peer (P2P) and Grid services, are continuously emerging, whilst information can be collected from several information sources, e.g. materializations of the Web 2.0 and Web 3.0 trends, Social Networking apps and Sensor Networks. Within this context the development of adaptable service oriented processes utilizing heterogeneous services, in addition to available information, is an emerging trend. This paper presents an approach and an enabling architecture that leverage the provision of data-driven, adaptable, heterogeneous service processes. Core within the proposed architecture is a set of interacting components that accommodate the acquisition of information, the execution of service chains and their adaptation, based on collected information.

This booklet is abstracted and abridged from “The Digital Technology and Methodology Cookbook”, D... more This booklet is abstracted and abridged from “The Digital Technology and Methodology Cookbook”, D3.4 DL.org Project Deliverable, April 2011

2008 12th Enterprise Distributed Object Computing Conference Workshops, 2008

Developments in service-oriented computing have led to the emergence of heterogeneous service tec... more Developments in service-oriented computing have led to the emergence of heterogeneous service technologies moving well beyond Web services, such as Peer-to-Peer (P2P) and Grid services. Although all these technologies instantiate the de-facto serviceoriented model, they introduce a number of technology-specific characteristics which hinder their integration and interoperability. A first step in overcoming this obstacle is to address the aforementioned heterogeneity at the design level. In this paper, we present our work towards enriching the upcoming SOA-Pro profile, which supports the design of service-oriented systems in a platform-agnostic manner, with the concepts necessary to model P2P and Grid services. We propose a set of extensions, which capture the specific features of P2P and Grid services, as they are seen in two prominent representative platforms, namely the JXTA technology for P2P services, and the WSRF framework for Grid services. The applicability and merits of our contribution are demonstrated through a case study based on the Purchase Order example.

Service Oriented Computing is branded as the software engineering trend which will reshape the wa... more Service Oriented Computing is branded as the software engineering trend which will reshape the way distributed applications and systems are built. This new trend has reformed existing distributed application development paradigms such as grid and peer-to-peer (p2p) paradigms. Although, the notion of service has been firmly incorporated within the grid computing paradigm, the p2p computing paradigm has not ensued a similar approach. Hence, existing p2p computing frameworks and platforms have leveraged proprietary approaches in incorporating the notion of service.

Springer eBooks, Mar 8, 2006

Peer-to-peer (p2p) applications exhibit characteristics such as dynamic network topology and conf... more Peer-to-peer (p2p) applications exhibit characteristics such as dynamic network topology and configuration, heterogeneity and scalability that make their development a complicated task. This is further aggravated due to the required satisfaction of dependability properties, i.e. security, availability, reliability, etc. Furthermore, p2p application requirements are driven by the software architecture adopted for their development while in other kinds of applications, the requirements drive the architecture. It is therefore only natural to adopt an architecture-based approach for the development of p2p dependable applications in order to ensure at the architectural level that dependability requirements are met. An essential part for the effective architecture-based development is the use of an appropriate modelling mechanism. In this paper we argue on the use of a UML profile that provides appropriate constructs and notations for modelling dependable p2p software architectures.

Within the currently forming pervasive computing environment services and information sources thr... more Within the currently forming pervasive computing environment services and information sources thrive. Instantiations of the service oriented computing paradigm e.g. Web, Peer-to-Peer (P2P) and Grid services are continuously emerging, whilst information can be collected from several information sources e.g. materialisations of the Web 2.0 and Web 3.0 trends, Social Networking apps and Sensor Networks. Within this context the development of adaptable service oriented processes utilising heterogeneous services, in addition to available information is an emerging trend. This paper presents an approach and an enabling architecture that leverage the provision of data-driven, adaptable, heterogeneous service processes. Core within the proposed architecture is a set of interacting components that accommodate the acquisition of information, the execution of service chains and their adaptation based on collected information. 1 Dissertation Summary Our era has been marked by a shift in the way...

Στο υπό εξέλιξη διαδίκτυο, όπου ανθούν οι υπηρεσίες και οι πηγές πληροφορίας, η παροχή προσαρμοζό... more Στο υπό εξέλιξη διαδίκτυο, όπου ανθούν οι υπηρεσίες και οι πηγές πληροφορίας, η παροχή προσαρμοζόμενων υπηρεσιοστρεφών διαδικασιών οι οποίες εκμεταλλεύονται διαθέσιμες υπηρεσίες και πληροφορίες, αποτελεί επιτακτική ανάγκη και όχι απλά επιθυμητό χαρακτηριστικό. Στόχος των προσαρμοζόμενων διαδικασιών είναι η «χρήση διαθέσιμων πληροφοριών σχετικών με τις αλλαγές του περιβάλλοντος τους με σκοπό την βελτιστοποίηση της συμπεριφοράς τους». Στο σύνολο των τεχνικών που έχουν εφαρμοστεί ως τώρα μπορεί κανείς να αναγνωρίσει διάφορες κατηγορίες, όπως για παράδειγμα, τεχνικές από το χώρο της Τεχνητής Νοημοσύνης, τεχνικές από το χώρο της υπολογιστικής Πλαισίου, ή ακόμη από το χώρο της υπολογιστικής Όψεων. Ομοίως όταν κανείς εξετάζει το κύκλο ζωής διαδικασιών, εάν και η προσαρμογή μιας διαδικασίας είθισται να λαμβάνει χώρα κατά το χρόνο εκτέλεσης, είναι απαραίτητο να λαμβάνεται υπόψη το ‘πότε’ πραγματοποίούνται οι περισσότεροι υπολογισμοι, π.χ. κατά το χρόνο εκτέλεσης, το χρόνο σχεδιασμού ή το χρό...

International Journal of Spatial Data Infrastructures Research, Sep 16, 2010

Serving geographic information via standardized Web services has been widely accepted as a useful... more Serving geographic information via standardized Web services has been widely accepted as a useful approach. Web-enabled environmental models simulating real-world phenomena are, however, rare. The models predict observations traditionally served by geospatial Web services compliant to well-defined standards. Using standardized Web services could support decoupling of models, comparison of similar models, and the automatic integration into existing geospatial workflows. Modeling experts face several open issues when migrating existing environmental computer models to the Web. The selection of the Web service interface depends on the input parameters required for the successful execution of the computer model. Loosing control over the execution of the models, and consequently also the confidence in model results, can be addressed to a certain extent by using translucent and standardized workflow languages. Mechanisms and open problems for the implementation of geospatial Web service compositions are discussed. Two scenarios about oil spills and the exposure to air pollution illustrate the impact of unconfigured model parameters for standard-compliant spatial data clients.

Icsoft, 2006

Our era has been marked by the emergence of the service oriented computing (SOC) paradigm. This n... more Our era has been marked by the emergence of the service oriented computing (SOC) paradigm. This new trend has reshaped the way distributed applications are built and has influenced current computing paradigms, such as p2p and grid computing. SOC's main objective is to leverage interoperability among applications and systems; however, the emergence of various types of services such as web, grid and p2p services has raised several interoperability concerns among these services as well as within each of these service models. In order to surpass these incompatibilities, appropriate middleware and mechanisms need to be developed so as to provide the necessary layers of abstraction and a unified framework that will obscure a service user from the underlying details of each service platform. Yet, for the development of such middleware and mechanisms to be effective, appropriate conceptual models need to be constructed. Within this paper, we briefly present a generic service model which was constructed to facilitate the unified utilization of heterogeneous services, with emphasis on its properties for the modeling of p2p services. Moreover, we illustrate how this model was instantiated for the representation of JXTA services and present the service description and discovery mechanisms that were built upon it. We regard this generic service model as a first step in achieving interoperability between incompatible types of services.

Icsoft, 2010

Within the currently forming pervasive computing environment, services and information sources th... more Within the currently forming pervasive computing environment, services and information sources thrive. Instantiations of the service oriented computing paradigm, e.g. Web, Peer-to-Peer (P2P) and Grid services, are continuously emerging, whilst information can be collected from several information sources, e.g. materializations of the Web 2.0 and Web 3.0 trends, Social Networking apps and Sensor Networks. Within this context the development of adaptable service oriented processes utilizing heterogeneous services, in addition to available information, is an emerging trend. This paper presents an approach and an enabling architecture that leverage the provision of data-driven, adaptable, heterogeneous service processes. Core within the proposed architecture is a set of interacting components that accommodate the acquisition of information, the execution of service chains and their adaptation, based on collected information.

This booklet is abstracted and abridged from “The Digital Technology and Methodology Cookbook”, D... more This booklet is abstracted and abridged from “The Digital Technology and Methodology Cookbook”, D3.4 DL.org Project Deliverable, April 2011

2008 12th Enterprise Distributed Object Computing Conference Workshops, 2008

Developments in service-oriented computing have led to the emergence of heterogeneous service tec... more Developments in service-oriented computing have led to the emergence of heterogeneous service technologies moving well beyond Web services, such as Peer-to-Peer (P2P) and Grid services. Although all these technologies instantiate the de-facto serviceoriented model, they introduce a number of technology-specific characteristics which hinder their integration and interoperability. A first step in overcoming this obstacle is to address the aforementioned heterogeneity at the design level. In this paper, we present our work towards enriching the upcoming SOA-Pro profile, which supports the design of service-oriented systems in a platform-agnostic manner, with the concepts necessary to model P2P and Grid services. We propose a set of extensions, which capture the specific features of P2P and Grid services, as they are seen in two prominent representative platforms, namely the JXTA technology for P2P services, and the WSRF framework for Grid services. The applicability and merits of our contribution are demonstrated through a case study based on the Purchase Order example.

Service Oriented Computing is branded as the software engineering trend which will reshape the wa... more Service Oriented Computing is branded as the software engineering trend which will reshape the way distributed applications and systems are built. This new trend has reformed existing distributed application development paradigms such as grid and peer-to-peer (p2p) paradigms. Although, the notion of service has been firmly incorporated within the grid computing paradigm, the p2p computing paradigm has not ensued a similar approach. Hence, existing p2p computing frameworks and platforms have leveraged proprietary approaches in incorporating the notion of service.