Blockchain or Distributed Ledger Technology is a disruptive technology that
provides the infrastructure for developing decentralized applications enabling
the implementation of novel business models even in traditionally centralized
domains. In the last years it has drawn high interest from the academic
community, technology developers and startups thus lots of solutions have been
developed to address blockchain technology limitations and the requirements of
applications software engineering. In this paper, we provide a comprehensive
overview of DLT solutions analyzing the addressed challenges, provided
solutions and their usage for developing decentralized applications. Our study
reviews over 100 blockchain papers and startup initiatives from which we
construct a 3-tier based architecture for decentralized applications and we use
it to systematically classify the technology solutions. Protocol and Network
Tier solutions address the digital assets registration, transactions, data
structure, and privacy and business rules implementation and the creation of
peer-to-peer networks, ledger replication, and consensus-based state
validation. Scaling Tier solutions address the scalability problems in terms of
storage size, transaction throughput, and computational capability. Finally,
Federated Tier aggregates integrative solutions across multiple blockchain
applications deployments. The paper closes with a discussion on challenges and
opportunities for developing decentralized applications by providing a
multi-step guideline for decentralizing the design of traditional systems and
implementing decentralized applications.Comment: 30 pages, 8 figures, 9 tables, 121 reference
