# Distributed Ledger Technology Review and Decentralized Applications Development Guidelines
## 6 Conclusions  
The distributed ledger technology has the potential of being a game-changer in many domains, its recent developments being triggered not only by technology expectations but also by social ones. DLTs have enabled the development of decentralized applications but this process is still complicated due to the high availability of new and rather immature technological solutions that address different implementation issues. DLTs and especially blockchain are an effervescent innovation area. Therefore, the review of technological solutions and implementation guidelines are needed to improve understanding and to ease the development of decentralized applications. Most of the similar initiatives found in the literature are focusing on the blockchain-based distributed ledger and pay little attention to other DLT implementations. In this paper, we have provided a review of the existing DLT solutions. We highlight their applicability, advantages, and disadvantages concerning other technologies. A significant number of solutions have been reviewed to provide a holistic image of the DLT implementation variations. In the technology review process, we have considered references from both academia and the private sector. At the same time, our review was driven by a decentralized application architecture that has been used and validated in previous publications. The DLT solutions are categorized according to the 3-tiers of the architecture thus the criteria for selecting the technologies and organizing the review are strictly related to the development issues that may be encountered and need to be addressed in each tier. Finally, we provide a guideline for decentralized application development defining specific steps for decentralizing a system design and business model using DLT and for implementing and launching it as a decentralized application. No similar guideline could be found in the reviewed literature. The guideline can be used to streamline the nowadays efforts for investigating how the DLT can be applied, integrated, and used for decentralizing systems such as medical systems, electricity grids, financial sector, etc., and for implementing new decentralized applications. \begin{table}
\begin{tabular}{c c c c} \hline
**Issue** & **Tier** & **Description** & **Alternative Solutions** \\ \hline \multirow{3}{*}{**Business** **Enforcement**} & \multirow{3}{*}{PN-Tier} & Built-in custom business rules & Filecoin [112], NRGCoin [24] \\ \cline{3-4}  & & Generic rules and pluggable Turing & Ethereum [15], Hyperledger [34] \\ \cline{3-4}  & & Complete implementation & \\ \hline \multirow{3}{*}{**Data Propagation**} & \multirow{3}{*}{PN-Tier} & Selective disclosure & Hyperledger Multichannel (Corda [61], Plasma [62]), Quorum [49] \\ \cline{3-4}  & & Global disclosure & Any public permissionless DLT \\ \hline \multirow{3}{*}{**Permissions \& Consensus** **\&
\begin{tabular}{c} Public Permissionless \& \\ Byzantine Fault Tolerance \\ \end{tabular} } & Ethereum with PoS or PoW \\ \cline{3-4}  & & Public Permissioned & Ethereum PoS or PoA; Hyperledger [34] \\ \cline{3-4}  & & Consortium or Private & Hyperledger [34], Corda [61] \\ \hline \multirow{3}{*}{**Large Size data**} & \multirow{3}{*}{PN-Tier} & Selection of Scalability and & BigChainDB [20] \\ \cline{3-4}  & & Decentralisation over Security & \\ \cline{3-4}  & & File System Storage & IPPS [111], Storj [110], Filecoin [112] \\ \hline \multirow{3}{*}{**High-Frequency** **Data**} & \multirow{3}{*}{PN-Tier/S-Tier} & Selection of Scalability and Security over & \multirow{3}{*}{IOTA [16], Sharding [104], Sidedains [121]} \\  & & Decentralization & \\ \cline{3-4}  & & Overlay Networks; Payment/State & Payment Channels [124], Raiden [125] \\ \hline \multirow{3}{*}{**Computational** **Intensive Algorithms**} & \multirow{3}{*}{PN-Tier/S-Tier} & Selection of Scalability and Security over & **Secure Multi-Party Computation**: Enigma [133]; \\  & & Decentralization & TrueBit [129] \\ \cline{3-4}  & & Oracles & Provable [128] \\ \hline \end{tabular}
\end{table}