In a blockchain-based system, data and the consensus-based process of recording and updating them over distributed nodes are central to enabling the trustless multi-party transactions. Thus, properly understanding what and how the data are stored and manipulated ultimately determines the degree of utility, performance, and cost of a blockchain-based application. While blockchains enhance the quality of the data by providing a transparent, immutable, and consistent data store, the technology also brings new challenges from a data management perspective. In this paper, we analyse blockchains from the viewpoint of a developer to highlight important concepts and considerations when incorporating a blockchain into a larger software system as a data store. The work aims to increase the level of understanding of blockchain technology as a data store and to promote a methodical approach in applying it to large software systems. First, we identify the common architectural layers of a typical software system with data stores and conceptualise each layer in blockchain terms. Second, we examine the placement and flow of data in blockchain-based applications. Third, we explore data administration aspects for blockchains, especially as a distributed data store. Fourth, we discuss the analytics of blockchain data and trustable data analytics enabled by blockchain. Lastly, we examine the data governance issues in blockchains in terms of privacy and quality assurance.

The construction industry has dynamic supply chains with multiple suppliers usually engaged in short-term relationships. Government legislation, novel types of payment agreements, conventional information technology solutions, and supply chain management best practices have endeavoured to solve payment-related financial issues in the construction industry, which are mainly caused by the complexities of the construction supply chain. Nevertheless, payment-related issues persist as one of the key challenges in the industry. Applications of blockchain technology–a trusted, distributed data storing mechanism–along with smart contracts are gaining focus as solutions for complex interorganisational processes. A smart contract is a self-executing script that codifies a set of rules or agreements between multiple parties and runs across the blockchain network. This paper identifies the suitability of blockchain and smart contract technologies in solving payment issues in the construction industry. An expert forum of construction industry stakeholders served as the primary data collection method through a structured questionnaire. The key finding of the paper is that blockchain and smart contract powered solutions can significantly mitigate the payment and related financial issues in the construction industry, including partial payments, nonpayments, cost of finance, long payment cycle, retention, and security of payments.

The rise of data-sharing platforms, driven by public demand for open data and legislative mandates, has raised several pertinent issues. These encompass uncertainties over data accuracy, provenance and lineage, privacy concerns, consent management, and the lack of equitable incentives for data providers. The advanced nature of blockchain makes it well suited to address these concerns. Yet, the limitations of blockchains, particularly their restricted performance, scalability, and high cost, make them less adept at managing the four “Vs” of big data—volume, variety, velocity, and veracity. As the body of work proposing blockchain-based data-sharing solutions grows, so does the confusion in selecting between these platforms, particularly in terms of sharing mechanisms, services, quality of services, and applications. In this article, we aim to fill this knowledge gap through an in-depth survey of blockchain-based data-sharing architectures and applications. We first identify the key challenges of existing data-sharing techniques and lay out the foundations of blockchains. Our focus then shifts to the intersection of blockchain and data sharing, wherein we aim to clarify the existing landscape and propose a reference architecture for blockchain-based data sharing. Subsequently, we explore various industrial applications of blockchain-based data sharing, spanning healthcare, smart grids, transportation, and decarbonization. For each application, we draw from real-world deployments to present key lessons learned in the implementation of blockchain-based data sharing. Lastly, we shed light on current research challenges and open avenues for further study in this space. This article aims to serve as a comprehensive resource for researchers/practitioners looking to navigate the complex terrain of blockchain-based data-sharing solutions.

Although a massive amount of bandwidth is available at mm-waves, physics dictates the use of legacy frequencies in the sub 6-GHz range. This necessitates dynamic spectrum access in the face of exponentially growing spectral demands. However, disorganized spectrum sharing causes interference, leads to a chaotic situation, and loss of capacity. Moreover, it is difficult to ensure that the primary users are compensated for sharing their licensed bands. We propose a Blockchain-based platform to address these limitations. A digital token, called spectral token, is introduced to validate and track the use of a licensed frequency band while enforcing sequential access to spectrum by secondary users to avoid interference. The proposed platform enables both advertising and sensing based spectrum sharing under different leasing policies. Such sharing and leasing policies are coded into smart contracts, which digitally enforce the contractual clauses of the leasing agreement. When a deal is made, the smart contract automatically transfers the spectral token between primary and secondary users within the agreed time frame while paying the primary user in cryptocurrency. We developed a proof of concept solution using the Ethereum Blockchain to demonstrate the utility of the proposed platform and its throughput and latency characteristics.

With the rapid evolution of technological, economic, and regulatory landscapes, contemporary blockchain platforms are all but certain to undergo major changes. Therefore, the applications that rely on them will eventually need to migrate from one blockchain instance to another to remain competitive and secure, as well as to enhance the business process, performance, cost efficiency, privacy, and regulatory compliance. However, the differences in data and smart contract representations, modes of hosting, transaction fees, as well as the need to preserve consistency, immutability, and data provenance introduce unique challenges over database migration. We first present a set of blockchain migration scenarios and data fidelity levels using an illustrative example. We then present a set of migration patterns to address those scenarios and the above data management challenges. Finally, we demonstrate how the effort, cost, and risk of migration could be minimized by choosing a suitable set of data migration patterns, data fidelity level, and proactive system design. Practical considerations and research challenges are also highlighted.

Blockchains have been applied in different domains to guarantee data integrity and provide a decentralized computational infrastructure for executing smart contracts. Multiple blockchain-related patterns have been summarized by academics and industry practitioners covering different aspects, such as engineering applications on top of a blockchain, structuring smart contracts, and security. The existence of these patterns is both helpful and challenging for designers. Helpful, as the existence of these patterns means that developers do not need to recreate solutions to common problems. Challenging, as the multitude of patterns leaves a designer confused about when to adopt or adapt patterns. In this paper, we propose a decision model that assists developers and architects in selecting appropriate patterns for blockchain-based applications. The selection is based on the characteristics of the use cases and trade-offs implicit in the patterns. We evaluated the proposed decision model based on expert opinion regarding its correctness and usefulness in guiding the architecture design and understanding the rationale of various design decisions.