Sylvia Ilieva

Sofia University "St. Kliment Ohridski", Software Engineering (http://dse.fmi.uni-sofia.bg/), Faculty Member

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Papers by Sylvia Ilieva

Self-Adaptive Software Systems through Exploratory Changes

Springer eBooks, 2011

Most of the research in self-adaptive software systems is concerned with self-adaptation as respo... more

Digital Twin Modeling of Smart Cities

Human Interaction, Emerging Technologies and Future Applications III, 2020

Smart cities utilize the Big Data and IoT to provide better life for citizens. Since, they are th... more Smart cities utilize the Big Data and IoT to provide better life for citizens. Since, they are the most complicated human artifact, the adoption of such technologies become a complex task, requiring continuous data collection, aggregation and analysis. In order to transform city problems into concrete actions a systematic approach aimed at digital transition needs to be followed. There are huge efforts to build city information models for encoding city objects, their relations and supporting the decision-making. This requires a common knowledge base, supported by rich vocabularies and ontologies that are capable to handle the information diversity and overload. In this paper a methodological framework and an upper-level ontology for building digital city models are presented. The process of digital city modelling follows the concept of digital twin by providing a data-driven decision making. The proposed upper-level ontology aims to overcome city modeling problems due to data silos and lack of semantic interoperability.

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An architectural approach for dynamic web service composition

ABSTRACT Service-oriented architecture (SOA) is one of the latest computing paradigms where the c... more ABSTRACT Service-oriented architecture (SOA) is one of the latest computing paradigms where the components of software systems are replaced with services accessed over the network and often implemented as web services. Consuming web services in distributed environment entails a wide range of composition, reconfiguration, negotiation and trust issues that bring new research and development challenges. Although various approaches and frameworks for web service composition exist, there is still lack of solutions, which produce executable business processes through dynamic negotiation with service providers, adequate service level agreements (SLAs) and automatic composition of reliable services. Furthermore, there is no answer to the question of what happens with a web service composition when the client requirements for quality of service (QoS) are changed or SLAs are violated. To address these challenges, we propose an architectural view of a platform for dynamic web service composition supporting automatic generation of SLAs from the client requirements, negotiation with web service providers and QoS-aware building of executable business processes.

AI-Based Hybrid Data Platforms

Springer eBooks, 2022

The current digital transformation of many businesses and the exponential growth of digital data ... more The current digital transformation of many businesses and the exponential growth of digital data are two of the key factors of digital revolution. For the successful meeting of high expectations, the data platforms need to employ the recent theoretical, technological, and methodological advances in contemporary computing and data science and engineering. This chapter presents an approach to address these challenges by combining logical methods for knowledge processing and machine learning methods for data analysis into a hybrid AI-based framework. It is applicable to a wide range of problems that involve both synchronous operations and asynchronous events in different domains. The framework is a foundation for building the GATE Data Platform, which aims at the application of Big Data technologies in civil and government services, industry, and healthcare. The platform implementation will utilize several recent distributed technologies such as Internet of Things, cloud, and edge computing and will integrate them into a multilevel service-oriented architecture that supports services along the entire data value chain, while the service orchestration guarantees a high degree of interoperability, reusability, and automation. The platform is designed to be compliant with the opensource software, but its open architecture supports also mixing with commercial components and tools.

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Enabling City Digital Twins Through Urban Living Labs

The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, May 30, 2022

The population density in urban areas is rapidly rising, leading to a constant need for new infra... more The population density in urban areas is rapidly rising, leading to a constant need for new infrastructure and services for citizens. To reduce the time to implementation and optimise the monetary cost of various solutions, the plans and policies of local authorities and stakeholders would benefit from undergoing a series of virtual stress tests. To this end, prescriptive and predictive technologies are widely adopted to optimise city planning and to understand the urban processes and environment such as air pollution and transportation. Nevertheless, holistic sandboxes tightly integrated with cities are still largely lacking. The city digital twin is a promising concept that provides a tool for exploration of new solutions in a controlled environment before their deployment. The digital twin is a virtual replica of the real city, which collects data from the infrastructure, processes and services using not only the available systems, but also purposely built connected devices and sensors. In this context, the establishment of urban living labs facilitates the monitoring and understanding of urban processes and enriches the digital twin with highly-relevant data. This paper presents an urban living lab, under deployment in the district of Lozenets in Sofia, Bulgaria. It is part of a larger initiative for developing a city digital twin of Sofia to support the design, exploration, and experimentation of different solutions. The living lab is equipped with sensors for monitoring air quality, atmospheric parameters, noise pollution and pedestrian flows. In addition, a Light Detection and Ranging (LiDAR) system is realised as an edge computing facility at one of the busiest intersections of the district. Along with the equipment, the paper describes the architecture and components of the platform for data collection, storage, processing, and visualization. Finally, high-priority studies are presented, and their demographic and economic impact is discussed.

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System level modeling of component based software systems

One of the main problems in the area of Component-Based Software Engineering (CBSE) is how to fac... more One of the main problems in the area of Component-Based Software Engineering (CBSE) is how to facilitate the integration of software components into large-scale and complex systems. A possible solution is to enforce on software architecture of the system. The increased importance of architecture in CBSE raises the necessity to explore and develop methods for its formal description. Several languages and notations, named architecture description languages (ADL), were developed for formal system level specification. This paper overviews them and outlines the main directions for their evolution.

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Digital Twin Modeling of Smart Cities

Advances in intelligent systems and computing, Aug 6, 2020

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Framework for Testing Service Compositions

ABSTRACT Service Oriented Architecture (SOA) provides a new generation of software architectures ... more ABSTRACT Service Oriented Architecture (SOA) provides a new generation of software architectures that attracts attention as promising way for smooth integration of loose coupled software applications. In addition to all benefits, it adds new dimensions to the complexity of designing, building, testing, deploying and maintaining Service-based applications (SBA). Research in verification and validation applied to compositions of web services still is not mature enough. In this paper we present a framework named TASSA for testing, and validation of both functional and non-functional behavior of service-based applications. The paper focuses on one of the TASSA tools named Isolation tool. The framework is based on SOA principles and is composable depending on user requirements.

Smart Cities Evaluation – A Survey of Performance and Sustainability Indicators

Nowadays, the cities continuously attract new residents and become preferable places to live. The... more Nowadays, the cities continuously attract new residents and become preferable places to live. They provide better quality services in transportation, healthcare and education compared to villages. The cultural diversity and tourist attractiveness of the cities is also greater than the rural areas. At the same time, due to urbanization the cities meet a lot of challenges affecting both their economic performance and well-being. Some of them, like higher prices of services and goods might be directly measured, and others, such as pollution, traffic congestion and limited parking spaces, are difficult to quantify in term of cost. This paper examines the research efforts towards establishing a framework of indicators to monitor and assess the performance and sustainability of smart cities. It presents an analysis of the currently available smart city indicators (SCIs) by classifying them in six thematic areas, namely Smart Nature, Smart Living, Smart Mobility, Smart Governance, Smart People and Smart Economy.

Towards a Unifying View of QoS-Enhanced Web Service Description and Discovery Approaches

arXiv (Cornell University), Jun 26, 2009

The number of web services increased vastly in the last years. Various providers offer web servic... more The number of web services increased vastly in the last years. Various providers offer web services with the same functionality, so for web service consumers it is getting more complicated to select the web service, which best fits their requirements. That is why a lot of the research efforts point to discover semantic means for describing web services taking into account not only functional characteristics of services, but also the quality of service (QoS) properties such as availability, reliability, response time, trust, etc. This motivated us to research current approaches presenting complete solutions for QoS enabled web service description, publication and discovery. In this paper we present comparative analysis of these approaches according to their common principals. Based on such analysis we extract the essential aspects from them and propose a pattern for the development of QoS-aware service-oriented architectures.

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Generalized Nets Model of an E-Learning System Software Architecture

Serdica Journal of Computing, Sep 26, 2007

Component-based software engineering and software architecture are tightly connected areas in com... more Component-based software engineering and software architecture are tightly connected areas in computer science. Software architecture presents the functionality of the system as decomposition into components, the properties of these components and the connectors between them. This paper illustrates a methodology for application of the theory of Generalized Nets (GNs) as a language for description of software systems architecture. According to this methodology, every component in the system, as well as every connector is represented by a single GN transition. This way the positions of the transition describe the ports of components and connectors in the system. This paper introduces a model of the component-based architecture of the e-learning system ARCADE, which is created, with respect to the proposed methodology for description with GNs. The four main subsystems are regarded as components in the GNs model. Their additional sub-modules are presented as the services provided by the components. Method calls are regarded as the connectors between these components. Further, the GNs model is compared with the existing UML diagrams, specifying the design of ARCADE.

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TESSI: A web service testing tool: Demonstration paper

ABSTRACT Testing of Service-Oriented Architecture (SOA) implementations brings various challenges... more ABSTRACT Testing of Service-Oriented Architecture (SOA) implementations brings various challenges at infrastructure, service as well as orchestration level. In order to address these challenges the TASSA framework was developed for testing of web service orchestrations. The paper is focused on one of the TASSA framework tools, named TESSI (TESting of Service Implementations), providing test case generation, execution and management. The core functionality of the TESSI tool includes generation of SOAP request templates, definition of assertions at HTTP, SOAP and BPEL variable levels, support of data driven testing, test execution and management. Its first prototype is implemented as an open source plug-in for NetBeans IDE.

Towards a Technological Platform for Transparent and Flexible Assessment of Smart Cities

The concept of smart cities is widely accepted as a powerful tool to improve living standards in ... more The concept of smart cities is widely accepted as a powerful tool to improve living standards in all city dimensions. Smart cities aim to provide better quality services in the field of health, transport, energy and education in order to increase the comfort of their citizens. Whether in the planning or implementation phase, a key success factor for building smart cities is measuring the productivity of the decisions and obtaining an assessment of the final results. Most cities perceive the smart city concept, many of them are working on strategies for its implementation and more and more of them take concrete actions for deployment of "smart" solutions. Two questions arise from this: "What are the challenges to become a smart city?" and "What the city undertakes to become smart?". Their answers required assessment of the of city's "smart services" and the social effect of deployment of "smart solutions" during the transformation from "smart" plan to "smart" process. In such a context, this paper proposes an architecture of technological platforms for assessment of city's "smartness". Its primary goal is to provide a transparent and flexible indicator framework that supports quantitative progress evaluation of smart city strategy implementation, feedback on efficiency of current policies, timely and informed decision making and increased understanding of future city challenges. The main building components of the platform, namely repository, web APIs and web user interface, are described. Additionally, a classification schema of indicators covering six main thematic areas is proposed.

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Personal Extreme Programming – An Agile Process for Autonomous Developers

Despite the tendency of growing the size and complexity of the developed software, significant pa... more Despite the tendency of growing the size and complexity of the developed software, significant part of it is still developed by autonomous developers. The current research study proposes a modification of PSP which aims at lightening the software development process and making it easier to follow, while keeping the PSP basic principles. The new methodology is extended with proven efficient development practices from the Extreme Programming in order to support better project planning and product quality control. The paper presents the results of methodology adoption and compares it to ad-hock development.

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DDAT: Data Dependency Analysis Tool for Web Service Business Processes

Springer eBooks, 2011

Service Oriented Architecture (SOA) provides a new generation of software architectures intended ... more Service Oriented Architecture (SOA) provides a new generation of software architectures intended to integrate loosely coupled applications. In order to meet changing business goals, SOA systems incorporate multiple independent services supported by various providers. The complex structure of the resulting business processes can be defined in Business Process Execution Language for Web Services (WS-BPEL). One of the main tasks of

Automation of Test Case Generation and Execution for Testing Web Service Orchestrations

Efficient Speed-Up of Radial Basis Functions Approximation and Interpolation Formula Evaluation

Computational Science and Its Applications – ICCSA 2020, 2020

This paper presents a method for efficient Radial basis function (RBF) evaluation if compactly su... more This paper presents a method for efficient Radial basis function (RBF) evaluation if compactly supported radial basis functions (CSRBF) are used. Application of CSRBF leads to sparse matrices, due to limited influence of radial basis functions in the data domain and thus non-zero weights (coefficients) are valid only for some areas in the data domain. The presented algorithm uses space subdivision which enables us to use only relevant weights for efficient RBF function evaluation. This approach is applicable for 2D and 3D case and leads to a significant speed-up. This approach is applicable in cases when the RBF function is evaluated repeatably.

Using Big Data Value Chain to Create Government Education Policies

Proceedings of the 19th International Conference on Computer Systems and Technologies

The Big Data Value Chain aims to discover patterns, correlations, and pattern deviations hidden i... more The Big Data Value Chain aims to discover patterns, correlations, and pattern deviations hidden in a dataset. This paper investigates (1) the possible approaches to applying Big Data Value Chain to decision making in the Public sector, specifically in Education; and (2) the ways in which such activities can be automated. The models created can be customized depending on a school's dropout rate and number of students with learning difficulties. This research is part of a current project at the Ministry of Education and Science (MES) of Bulgaria, funded by the Operational Programme Science and Education for Smart Growth which aims to increase student engagement.

Modelling of Educational Data Following Big Data Value Chain

Proceedings of the 18th International Conference on Computer Systems and Technologies

Big Data is attracting increasing amount of attention among academy, industry and citizens. It po... more Big Data is attracting increasing amount of attention among academy, industry and citizens. It poses both opportunities and challenges for society as a whole. In order to gain value from Big Data, it needs to be processed and analysed in an appropriate way, and the results have to be presented in a visual manner as to be able to effectively support decision making. Following the current trends in Big Data, this paper aims to prove the value-creation of Big Data by proposing a new data model in the field of the primary and secondary education in Bulgaria. It follows the Big Data Value Chain concept in order to group the schools depending on the concentration of students with learning deficits and risk of premature leaving the education system. The primary purpose of the proposed Data Model is to drive decisions by turning information into intelligence.

A Framework for Design-Time Testing of Service-Based Applications at BPEL Level

Serdica Journal of Computing

Software applications created on top of the service-oriented architecture (SOA) are increasingly ... more Software applications created on top of the service-oriented architecture (SOA) are increasingly popular but testing them remains a challenge. In this paper a framework named TASSA for testing the functional and non-functional behaviour of service-based applications is presented. The paper focuses on the concept of design time testing, the corresponding testing approach and architectural integration of the consisting TASSA tools. The individual TASSA tools with sample validation scenarios were already presented with a general view of their relation. This paper’s contribution is the structured testing approach, based on the integral use of the tools and their architectural integration. The framework is based on SOA principles and is composable depending on user requirements.

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