This article focuses on the concept of blockchain soulbound tokens, their potential applications, and their implementation in Ethereum-based blockchains. Soulbound tokens add an important piece to blockchain technology, as they could be the key to building Web3 and a trustworthy decentralized society. Issued and strictly linked to an account, representing the soul of a user, the soulbound token makes it possible to represent a property that only the user can have and that cannot be transferred, but only removed, which enhances security. To evaluate their impact on blockchain development, we first examine the concept of soulbound tokens, their potential applications, and their effective adoption. The application sectors include the creation of digital identity certificates, ownership certificates, reputational certificates, governance, and the healthcare sector. We then report and describe relevant blockchain token standards, including soulbound token standards, provided in the form of Ethereum Improvement Proposals. Finally, to study the efficacy of the implementation of soulbound tokens, we propose a case study that includes the design and development of a decentralized vaccine certification prototype based on soulbound tokens. In our system, the vaccination data produced by the health authority is fully decentralized and implemented as the issuance of soulbound tokens for the benefit of a citizen’s soul account. As a result, the citizen is the only owner of the vaccination data.

The use of blockchain oracles is becoming increasingly widespread as it responds to the problem of providing the blockchain with external data automatically. In this paper, we focus on the use of blockchain oracles for the certification of articulated data. In particular, we show how it is possible to design and implement a DApp capable of providing documents on request without these data permanently residing on the blockchain. We present a case study of the on-demand provision of university curriculum, fully managed via a blockchain oracle. In this system, the smart contract will not record data permanently but only for the time necessary for its use. The system is intended to allow a user to request and obtain data only about herself. The paper also presents a classification of the types of blockchain oracles and their most common applications. The case study will be presented as blockchain-oriented software, and in terms of architecture and dynamics using UML diagrams, the benefits and drawbacks of the approach are discussed.

Nowadays, Internet of Things (IoT) applications are widespread in different scenarios, such as industry, mobility, healthcare, and agriculture. A relevant share of the credit is due to the Blockchain technology, which provides important features to IoT services, such as decentralized validation of transactions as well as immutability and traceability of the transactions. In this paper, we propose a Blockchain-based data notarization system for mobility services. First, we present an IoT-based crowd monitoring system aimed at counting the number of people in a specific area and providing information regarding people mobility (i.e., how people move within the city) and dwell time (i.e., the time people stayed at specific places). Then, we discuss our proposed data notarization system focused on ensuring data integrity and immutability of the mobility data collected by the crowd monitoring system, regardless of the used Blockchain. Finally, we provide experimental results regarding people mobility data collected during a literary event as well as an implementation of the proposed data notarization system using the EthernaZero blockchain.

Blockchain and the programs running on it, called smart contracts, are increasingly applied in all fields where trust and strong certifications are required. Our work focuses on industrial applications of blockchains and not on cryptocurrencies or tokens. We use frameworks to compare public and permissioned blockchains specifically suited for industrial applications. We also propose a complete solution based on Ethereum to implement a decentralized application, putting together in an original way, components and patterns already used and proven. This solution is characterized by a set of validator nodes running the blockchain using Proof-of-Authority or similar efficient consensus algorithms, by the use of an explorer enabling users to check the blockchain state, and the source code of the smart contracts running on it. From time to time, the hash digest of the last mined block is written into a public blockchain to guarantee immutability. The right to send transactions is granted by validator nodes to users by endowing them with the Ethers mined locally. Overall, the proposed approach has the same transparency and immutability as a public blockchain, largely reducing its drawbacks.

Context: Organizations increasingly develop software in a distributed manner. The Cloud provides an environment to create and maintain software-based products and services. Currently, it is unknown which software processes are suited for Cloud-based development and what their effects in specific contexts are. Objective: We aim at better understanding the software process applied to distributed software development using the Cloud as development environment. We further aim at providing an instrument, which helps project managers comparing different solution approaches and to adapt team processes to improve future project activities and outcomes. Method: We provide a simulation model, which helps analyzing different project parameters and their impact on projects performed in the Cloud. To evaluate the simulation model, we conduct different analyses using a Scrumban process and data from a project executed in Finland and Spain. An extra adaptation of the simulation model for Scrum and Kanban was used to evaluate the suitability of the simulation model to cover further process models. Results: A comparison of the real project data with the results obtained from the different simulation runs shows the simulation producing results close to the real data, and we could successfully replicate a distributed software project. Furthermore, we could show that the simulation model is suitable to address further process models. Conclusion: The simulator helps reproducing activities, developers, and events in the project, and it helps analyzing potential tradeoffs, e.g., regarding throughput, total time, project size, team size and work-in-progress limits. Furthermore, the simulation model supports project managers selecting the most suitable planning alternative thus supporting decision-making processes.

[Background] The effort required to systematically collect historical data is not always allocable in agile processes and historical data management is usually delegated to the developers' experience, who need to remember previous project details. However, even if well trained, developers cannot precisely remember a huge number of details, resulting in wrong decisions being made during the development process. [Aims] The goal of this paper is to operationalize the Experience Factory in an agile way, i.e., defining a strategy for collecting historical project data using an agile approach. [Method] We provide a mechanism for understanding whether a measure must be collected or not, based on the Return on Invested Time (ROIT). In order to validate this approach, we instantiated the factory with an exploratory case study, comparing four projects that did not use our approach with one project that used it after 12 weeks out of 37 and two projects that used it from the beginning. [Results] The proposed approach helps developers to constantly improve their estimation accuracy with a very positive ROIT of the collected measure. [Conclusions] From this first experience, we can conclude that the Experience Factory can be applied effectively to agile processes, supporting developers in improving their performance and reducing potential decision mistakes.

Requirements elicitation is the first crucial stage of a requirements engineering process, which intends to uncover, acquire and elaborate requirements for software systems. When software startups are concerned, requirements elicitation is particularly challenging due to the high uncertainty that a startup is confronted with. Few studies have investigated how software startups conduct requirements elicitation and what techniques are used in such a context. This study intends to address this knowledge gap. Three software startups from different part of the globe were studied. The findings reveal that the requirements elicitation process in startups is primordial and mainly informal, and it is an ongoing process alongside with product evolution. Software startups do employ established requirements elicitation techniques including interviews, prototyping and brainstorming. They also utilize other less common ones such as competitor analysis, collaborative team discussion and use of model users. This study highlights the market-driven nature of requirements that software startups have to deal with, and offers the first insights on the requirements elicitation techniques that could be relevant and applicable in the context of software startups.

Organizations increasingly develop software in a distributed manner. The Cloud provides an environment to create and maintain software-based products and services. Currently, it is widely unknown which software processes are suited for Cloud-based development and what their effects in specific contexts are. This paper presents a process simulation to study distributed development in the Cloud. We contribute a simulation model, which helps analyzing different project parameters and their impact on projects carried out in the Cloud. The simulator helps reproducing activities, developers, issues and events in the project, and it generates statistics, e.g., on throughput, total time, and lead and cycle time. The aim of this simulation model is thus to analyze the tradeoffs regarding throughput, total time, project size, and team size. Furthermore, the modified simulation model aims to help project managers select the most suitable planning alternative. Based on observed projects in Finland and Spain, we simulated a distributed project using artificial and real data. Particularly, we studied the variables project size, team size, throughput, and total project duration. A comparison of the real project data with the results obtained from the simulation shows the simulation producing results close to the real data, and we could successfully replicate a distributed software project. By improving the understanding of distributed development processes, our simulation model thus supports project managers in their decision-making.

The spread of the Social Web is influencing the evolution of Semantic Web: the way of producing and consulting information changes, as well as the way people relate themselves with the Internet and the services it gives. Users will participate at first hand to the developing of the Web which therefore becomes interactive. This study considers this feature, trying to link the worlds of Social Media and Semantic Web, with the aim of proposing a semantic classification of the information coming from the Web, which do not always follow a well-defined order and organization. Starting from a precise analysis of the information of the Web through an accurate and meticulous study on how these are presented and used, in order to give a sorted and easily usable data structure, this approach wants to define a taxonomy able to represent knowledge through an iterative combined approach, where top-down and bottom-up analyses are applied on the knowledge domain we want to represent

SUMMARY A software maintenance process is important for reducing maintenance effort and for improving software quality. In recent years, the Lean–Kanban approach has been widely applied in software practice including software maintenance. This approach minimizes Work‐in‐Progress (WIP), which is the number of items that are worked on by the team at any given time, thus improving the maintenance process. In this paper, we describe our simulation studies, which show that the Lean–Kanban approach can indeed help reduce the average time needed to complete maintenance requests. We develop a process simulator that can simulate both existing maintenance processes that do not use a WIP limit and that adopt it. We perform two case studies using real maintenance data collected from a Microsoft project and from a Chinese software firm. The main results of our study are twofold. First, we demonstrate that it is possible to effectively model and simulate, using actors and events, a maintenance process where a flow of issues is processed through a sequence of activities, correctly reproducing key statistics of real data. Second, our results confirm that the WIP‐limited process could be useful to increase the efficiency of software maintenance, as reported in previous industrial practices. Copyright © 2013 John Wiley & Sons, Ltd.