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In recent years, blockchain has been growing rapidly from a niche technology to a promising solution for many sectors, due to its unique properties that empower the design of innovative applications. Nevertheless, the development of blockchain applications is still a challenge. Due to the technological novelty, only a few developers are familiar with blockchain technologies and smart contracts. Others might face a steep learning curve or difficulties to reuse existing code to build blockchain applications. This study proposes a novel approach to tackle these issues, through software product line engineering. To support the approach, a web platform to configure and generate a blockchain application for on-chain traceability is introduced. First, a feature model has been designed to model core features of the chosen domain, based on the existing literature. Then, a configurator has been implemented to support the feature selection phase. Finally, a generator is able to ingest such configurations to generate on-the-shelf blockchain products. The generalizability of the contribution is validated by reproducing on-chain traceability applications proposed in the literature by using the platform. This work provides the first evidence that the implementation of blockchain applications using software product lines enhances the quality of produced applications and reduces the time to market., Comment: 26th ACM International Systems and Software Product Lines Conference, Sep 2022, Graz, Austria

Designing blockchain-based applications is a tedious task. Compared to traditional software engineering, software architects cannot rely on previous experiences or proven practices, often formalized as software patterns. Also, the selection of an adequate blockchain technology is difficult without deep knowledge of the technology. This paper introduces Harmonica, a framework for the design and implementation of a blockchain-based application. This framework is divided in three parts: a decision-making engine to recommend a blockchain technology and blockchain-based software patterns relying on requirements, a configurator to generate code stubs and configuration files, and a knowledge base to support those tools.

A software pattern is a reusable solution to address a commonly occurring problem within a given context when designing software. Using patterns is a common practice for software architects to ensure software quality. Many pattern collections have been proposed for a large number of application domains. However, because of the technology's recentness, there are only a few available collections with a lack of extensive testing in industrial blockchain applications. It is also difficult for software architects to adequately apply blockchain patterns in their applications, as it requires deep knowledge of blockchain technology. Through a systematic literature review, this paper has identified 120 unique blockchain-related patterns and proposes a pattern taxonomy composed of multiple categories, built from the extracted pattern collection. The purpose of this collection is to map, classify, and describe all available patterns across the literature to help readers make adequate decisions regarding blockchain pattern selection. This study also shows potential applications of those patterns and identifies the relationships between blockchain patterns and other non-blockchain software patterns.

Blockchain has been praised for its capacity to hold data in a decentralized and tamper-proof way. It also supports the execution of code through blockchain's smart contracts, adding automation of actions to the network with high trustability. However, as smart contracts are visible by anybody on the network, the business data and logic may be at risk, thus companies could be reluctant to use such technology. This paper aims to propose a pattern that allows the execution of automatable legal contract clauses, where its execution states are stored in an on-chain smart-contract and the logic needed to enforce it wraps it off-chain. An engine completes this pattern by running a business process that corresponds to the legal contract. We then propose a pattern-based solution based on a real-life use case: transportation of refrigerated goods. We argue that this pattern guarantees companies pseudonymity and data confidentiality while ensuring that an audit trail can be reconstituted through the blockchain smart-contract to identify misbehavior or errors. This paper paves the way for a future possible implementation of the solution described, as well as its evaluation.

In recent years, blockchain has grown in popularity due to its singular attributes, enabling the development of new innovative decentralized applications. But when companies consider leveraging blockchain for their applications, the plethora of possible choices and the difficulty of integrating blockchain into architectures can hinder its adoption. Our research project aims to ease the adoption of blockchain into companies, notably with the construction of an automated decision process to solve this issue in which requirements are first-class citizens, a knowledge base containing architectural patterns and blockchains refined over time, and an architecture generator able to process outputs into architectural stubs. This paper will also present our current progression on this decision process, by introducing the preliminary version that is able to choose the most suitable blockchain between multiple choices and our process-driven benchmarking tool.

Companies trying to build new solutions using blockchain are confronted with a plethora of available concurrent technologies that have many control knobs which require fine-tuning by experts. Exiting studies that build decision models for blockchain adoption or selection lack an automated way to use non-functional requirements to provide recommendations. In this paper, we build a knowledge base for blockchain solutions by analyzing whitepapers and studies, but also our benchmark results performed in a controlled environment. Then, we implement a Multi-Criterion Decision Analysis method to determine the most suitable blockchain solution from companies provided requirements and preferences. Finally, we illustrate our approach by running the decision process on a realistic supply-chain use case. This paper provides a rationale for blockchain deployment choices. While still limited in scope, we plan to include more blockchain alternative and more flexible requirements inputs in future work., Comment: in French