A fine-grained approach towards asynchronous service composition of heterogeneous services

In software design, a service-oriented architecture is a set of principles and methodologies used for designing and developing software in the form of interoperable services. Each service encapsulates well-defined business functionality and it is built as a reusable component. Thereafter, new services can be generated as a coordinated aggregate of pre-existing functionality by means of service composition. Common practice in the Information and Communication Technology domain (ICT) is the usage of standardized workflow languages in order to describe the interaction between such services. Examples of such languages are the Web Services Business Process and Execution Language (WS-BPEL) and the Business Process Modeling Language (BPMN). At runtime, a framework interprets the workflow and performs the actions mandated by the semantics of its constructs. Even though, a workflow language contains a sufficient amount of constructs to qualify as Turing complete, the usage of existing workflow languages along with their corresponding frameworks renders them cumbersome for rapid application development where one needs to combine services from heterogeneous domains and in particular when re-using pre-existing services originating from the telecommunications domain. More specifically, the limitations in the state of the art for workflow languages are encountered in aspects such as tight-technological coupling; interaction is limited to particular technologies, usage of static type systems - that hinder experimentation and finally yet importantly in terms of parallelism and concurrency, where the designer of a workflow is forced to manually define execution order in an attempt to utilize multiple cores which are commonly found in most computer systems nowadays. This dissertation introduces a novel language for service composition and a technology agnostic composition framework suitable for developing and executing service compositions of heterogeneous services. The proposed service composition language is concurrent by default; parallel execution of actions is determined by their corresponding data dependencies. The proposed framework allows for an optional type system permitting both typed and un-typed variables. Un-typed variables can be used while designing and experimenting with the composition in a trial and error fashion; while typed can be used once the model of the service composition matures and becomes production-ready. Moreover, the proposed composition framework employs a fine level of granularity while interpreting the constructs of the proposed language. Our qualitative evaluation of the proposed language has shown that it is capable of expressing a wide set of workflow patterns, making it as expressive as rival workflow languages. Empirical evaluations of the proposed fine-grained composition framework have shown that is scalable; limited only by the amount of available memory and not by the number of available processing threads

A fine-grained approach towards asynchronous service composition of heterogeneous services

In software design, a service-oriented architecture is a set of principles and methodologies used for designing and developing software in the form of interoperable services. Each service encapsulates well-defined business functionality and it is built as a reusable component. Thereafter, new services can be generated as a coordinated aggregate of pre-existing functionality by means of service composition. Common practice in the Information and Communication Technology domain (ICT) is the usage of standardized workflow languages in order to describe the interaction between such services. Examples of such languages are the Web Services Business Process and Execution Language (WS-BPEL) and the Business Process Modeling Language (BPMN). At runtime, a framework interprets the workflow and performs the actions mandated by the semantics of its constructs. Even though, a workflow language contains a sufficient amount of constructs to qualify as Turing complete, the usage of existing workflow languages along with their corresponding frameworks renders them cumbersome for rapid application development where one needs to combine services from heterogeneous domains and in particular when re-using pre-existing services originating from the telecommunications domain. More specifically, the limitations in the state of the art for workflow languages are encountered in aspects such as tight-technological coupling; interaction is limited to particular technologies, usage of static type systems - that hinder experimentation and finally yet importantly in terms of parallelism and concurrency, where the designer of a workflow is forced to manually define execution order in an attempt to utilize multiple cores which are commonly found in most computer systems nowadays. This dissertation introduces a novel language for service composition and a technology agnostic composition framework suitable for developing and executing service compositions of heterogeneous services. The proposed service composition language is concurrent by default; parallel execution of actions is determined by their corresponding data dependencies. The proposed framework allows for an optional type system permitting both typed and un-typed variables. Un-typed variables can be used while designing and experimenting with the composition in a trial and error fashion; while typed can be used once the model of the service composition matures and becomes production-ready. Moreover, the proposed composition framework employs a fine level of granularity while interpreting the constructs of the proposed language. Our qualitative evaluation of the proposed language has shown that it is capable of expressing a wide set of workflow patterns, making it as expressive as rival workflow languages. Empirical evaluations of the proposed fine-grained composition framework have shown that is scalable; limited only by the amount of available memory and not by the number of available processing threads

Computations on the Edge in the Internet of Things

In the Internet of Things (IoT), many applications focus on gathering data which can then be processed and visualized. However, such computations are usually spread generically based on parameters such as CPU and/or network load. This may mean that a significant amount of data needs to be transported over the network (either directly, or transparently using a network file system) in order for the data to be available to the node that is responsible for processing them. This paper proposes a method for deploying computations that can take factors such as data proximity into consideration. Thus, processing can be moved from central high-powered processing nodes to smaller devices on the edge of the network. By doing this, costs for gathering, processing and actuation can be minimized. In order to capture data dependencies among computations, but also to deploy and handle individual processing tasks in an easy way, the actor-model programming paradigm is used. To minimize the overall cost and to handle extra factors that weigh in on the distribution of tasks, a constraint programming approach is used. The combination of these two techniques results in an efficient distribution of tasks to processing resources in IoT. Taking into consideration the NP-hard nature of this problem, we present empirical results that illustrate how this technique performs in relation to the amount of devices/actors

Βασικά Δομικά στοιχεία για συστήματα πληροφορίας διαχυτής ευφυΐας

Recent research on Ambient Information Systems has explored the provision of information systems across a wide range of deployment contexts with emphasis on user mobility and location-oriented information delivery. Such work has resulted in a broad spectrum of concrete outcomes regarding design approaches for information presentation ?on the move? with primary emphasis on unobtrusive feedback, context-sensitive information mining and overall aesthetic quality. Additionally, the consolidation of such work seems to lead to somehow standardized technical vocabulary regarding the primary requirements of mobile information systems, the dominant software design patterns, micro and macro architectures, structure of information and the technical approaches to location sensing. However, there is no systematic work on addressing the implementation of these systems by proposing a universal set of basic building blocks and architectural elements. We argue that the general domain of ambient intelligence would significantly benefit from the identification of prominent building blocks for ambient information systems. The collection of building blocks is comprised of a data access layer, a location-sensing layer, a synchronization service and a mobile location-administration system. For each building block, we provide a systematic account of the main challenges it addresses in the context of ambient information systems. The data access layer provides a flexible mapping between physical artifacts within the environment and objects within the relational database. The location-sensing layer allows us to query the wireless infrastructure to retrieve user positions in real time. The synchronization layer allows us to ensure that information mirrored in distributed resources remains always up to date. Finally, the mobile location-administration system allows the administrator to interactively program -on site- the physical position of information elements.Πρόσφατες μελέτες για τα διάχυτα συστήματα πληροφοριών έχουν ασχοληθεί με την εξερεύνηση των μεθοδολογιών διάθεσης της πληροφορίας σε μια ευρεία κλίμακα σεναρίων με κυριότερη έμφαση σε αυτό όπου ο χρήστης βρίσκεται σε κίνηση και χρησιμοποιεί μια φορητή συσκευή για να λάβει πληροφορίες σχετικά με το περιβάλλον του και τις δυνατότητες που του παρέχει. Αυτές οι μελέτες έχουν αποδώσει μία πληθώρα παραδειγμάτων από σχεδιαστικές προσεγγίσεις όσον αφορά το πρόβλημα της παρουσίασης της πληροφορίας για τον κόσμο του χρήστη με τέτοιο τρόπο ώστε να μην του αποσπά την προσοχή από την τρέχουσα εργασία, αλλά να παρουσιάζετε με αισθητικά ευχάριστο και κατανοητό τρόπο σε ποικίλες βαθμίδες. Επιπρόσθετα, η σταθεροποίηση τέτοιων μελετών φαίνετε να έχει οδηγήσει στη συγκέντρωση ενός ενιαίου τεχνικού λεξιλογίου σχετικά με τις πρωτεύουσες απαιτήσεις για τα φορητά συστήματα πληροφοριών, τα κυρίαρχα πρότυπα σχεδίασης, τις μικρό / μάκρο αρχιτεκτονικές, τη δομή της πληροφορίας και τις τεχνικές προσεγγίσεις για τον εντοπισμό θέσης. Πάρα την επιτυχία όλων των παραπάνω, στην παρούσα βιβλιογραφία φαίνετε να απουσιάζει μια συστηματική προσέγγιση σχετική με την υλοποίηση τέτοιων συστημάτων η οποία θα πρότεινε ένα ενιαίο σύνολο από βασικά κατασκευαστικά τμήματα και στοιχεία αρχιτεκτονικής για τέτοια συστήματα. Υποστηρίζουμε ότι ο ευρύτερος χώρος των συστημάτων διάχυτης ευφυΐας θα μπορούσε να επωφεληθεί σημαντικά από την αναγνώριση των πρωταρχικών κατασκευαστικών τμημάτων για διάχυτα συστήματα πληροφοριών. Η εργασία αυτή προτείνει μια συλλογή κατασκευαστικών τμημάτων η οποία αποτελείται από ένα σχέδιο πρόσβασης δεδομένων, ένα σχέδιο εντοπισμού, μία υπηρεσία συγχρονισμού και ένα σύστημα φορητής αντιστοίχισης χωρικών σημείων. Κάθε τμήμα αναλαμβάνει να επιτύχει μια συστηματική αντιμετώπιση των προκλήσεων που αντιμετωπίζει. Το σχέδιο πρόσβασης δεδομένων παρέχει μία ευέλικτη διασύνδεση ανάμεσα στα φυσικά αντικείμενα του περιβάλλοντος και στην αναπαράσταση τους από αντικείμενα σχεσιακών βάσεων δεδομένων. Το σχέδιο εντοπισμού μας επιτρέπει να επερωτήσουμε την ασύρματη υποδομή δικτύου και να ανακτήσουμε τη θέση ενός αντικειμένου. Η υπηρεσία συγχρονισμού μας επιτρέπει να διασφαλίσουμε το γεγονός ότι κάθε πληροφορία που ανακλάται σε κατανεμημένες πηγές παραμένει πάντα επίκαιρη. Τέλος, το σύστημα φορητής διαχείρισης της αντιστοίχισης χωρικών σημείων παρέχει τη δυνατότητα στον διαχειριστή να αλληλεπιδράσει άμεσα με το περιβάλλον του και καταγράψει τις θέσεις των αντικειμένων που βρίσκονται γύρω του στον χώρο

QoE Modeling on Split Features with Distributed Deep Learning

The development of Quality of Experience (QoE) models using Machine Learning (ML) is challenging, since it can be difficult to share datasets between research entities to protect the intellectual property of the ML model and the confidentiality of user studies in compliance with data protection regulations such as General Data Protection Regulation (GDPR). This makes distributed machine learning techniques that do not necessitate sharing of data or attribute names appealing. One suitable use case in the scope of QoE can be the task of mapping QoE indicators for the perception of quality such as Mean Opinion Scores (MOS), in a distributed manner. In this article, we present Distributed Ensemble Learning (DEL), and Vertical Federated Learning (vFL) to address this context. Both approaches can be applied to datasets that have different feature sets, i.e., split features. The DEL approach is ML model-agnostic and achieves up to 12% accuracy improvement of ensembling various generic and specific models. The vFL approach is based on neural networks and achieves on-par accuracy with a conventional Fully Centralized machine learning model, while exhibiting statistically significant performance that is superior to that of the Isolated local models with an average accuracy improvement of 26%. Moreover, energy-efficient vFL with reduced network footprint and training time is obtained by further tuning the model hyper-parameters

NotationBased Ancient Greek Music Synthesis with

This paper describes an instrument that can compose a song using predicates of Ancient Greek Music. It employs the methodology and musical notation of this specific music system and at the same time, it provides a mapping mechanism that depicts the whole process to composition predicates of the usual notation of Western Music. The aim of this application is to facilitate the efforts of Ancient Greek Music researchers in getting closer to what Ancient Greek Music really was by parametrically performing melodic pieces. ARION provides ethnomusicology with an experimental tool for notation-based Ancient Greek Music synthesis. The project approaches Ancient Greek Music by introducing a virtual Ancient Greek singer, who is able to sing in the Ancient Greek accent, while a musical instrument accompanies him. An easy-to-use and functional interface is provided for adding music and lyrics in a composition, using modern or Ancient Greek symbols of writing and music. like West [15] and Pöhlmann [13] have managed to collect and organize a very large amount of documents and actual music scores and have given a scientific insight for a music system over 2000 years old. This project takes their work and tries to make a connection between that music and prevailing modern Western Music. A software instrument is produced, ARION, capable of reproducing whole songs both musically and vocally and the same time the user can experiment with the various scales, symbols and frequencies having the total freedom to “imagine ” and hear how AGM music really was. The graphical user interface of ARION can b