-Blockchain technology and smart contract development currently lacks clarity in its implementation. The complicated architecture of blockchain is an obstacle that developers face during design and implementation of blockchain-based systems. In this paper we propose a method based on Model Driven Architecture, which could be used for defining and specifying blockchain structure and behavior. Such approach could be used as one of the ways for describing blockchain-based systems in a more general language in order to facilitate blockchain development process.
INTRODUCTION
Blockchain is a decentralized, distributed database that is shared and replicated across all the parties participating in the network. It takes a form of a public ledger for the transactions contained in the chain [1]. The blockchain is made up of blocks, where each block contains a hash of the previous block, thus linking to it [2]. The main advantages provided by the blockchain are a peer-to-peer exchange (i.e. decentralization) and robust public record keeping with the possibility to eliminate the intermediary between parties [3].
Blockchain enables development of distributed software architecture where networks of untrusted participants can establish agreements on shared states for decentralized and transactional data in a secure way. Blockchain ensures trust among parties in decentralized systems without the need of centralized supervisor in charge of verifying the correctness of the records in the ledger [4]. Since blockchain digital currencies combine features of money with those of a payment system, central banks started to investigate the technology. From the industry side, over one hundred corporations have joined blockchain working groups or consortia and the number of patents filled increased to more than three thousand in 2017 [5].
Blockchain itself cannot handle large amount of information, because the main purpose is to store simple transactional logs. As a result, scalability of blockchain is a concern for the developers [4]. Even though the technology has been around for a while, there are only a few academic blockchain-related studies. Most of the available non© 2019 for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0) scientific papers about blockchain technology are whitepapers, documentations or technical documents; some of which may be incomplete or are still being updated. A practical approach to blockchain development also demands considerable investment [6]. Developers need to have a clear understanding of the capabilities and limitations of blockchain technology. Additionally, they need to acquire the necessary skills to implement the technology and to figure out how the new trust architecture would affect the application.
Currently, the blockchain technology is most broadly
applied for cryptocurrencies, but other areas are in early
adoption as well. Solutions for automating the insurance
process [7], supply chain management [
Modelling is a common tool for facilitating
communication, visualizing the development process and
even automating the implementation of some development
artefacts. The strategies of Model Driven Development [
In this paper we present our idea of blockchain technology development method, based on MDA principles. The proposed method could be used for different processes for the definition of common elements and the identification of potential application areas. The method could provide a more structured approach for the development of blockchain elements, which could potentially shorten the time of development. In the future we plan on developing the method further.
The rest of the paper is organized as follows. The second section discusses the background of blockchain technology and its evolution. The third section presents current areas of blockchain application and research on improving blockchainbased systems development process. The fourth section describes our proposition on applying principles of modeldriven architecture for blockchain system development. The last section summarizes concludes our main insights and outlines future work.
II.
BACKGROUND
This chapter presents the basic concepts and categories of blockchain technology. In this way, we intend to define the domain in order to outline a common understanding of these technologies and attain a more comprehensive communication in this area. Although the terms “blockchain” and “distributed ledger” are used interchangeably, the blockchain is a type of distributed ledger technology and blockchain mostly differs from distributed ledger in the way the data is stored [5]. For this reason, we refer to these technologies using the terms “blockchain” and “blockchain technologies” as they cover both concepts.
Blockchain is a distributed database that is shared across
participants [
The data in blocks are hash sealed. The participants can interact with the blockchain only by using a generated address so that the identity of the user is not revealed. Any transaction refers to some previous transactions. Once the current transaction is recorded into the blockchain, the state of referred transactions change. That way transactions can be tracked and verified once needed.
Participants in the network authenticate and approve transactions before inclusion to the blockchain. Few different methods for reaching consensus exist. Consensus algorithms in blockchain are used to maintain data consistency in a distributed network. Usually, the basis of such algorithms is that the majority of network participants needs to approve the correctness of transaction. This way the need for a third party is avoided. In a traditional centralized transaction system, each transaction needs to be validated by a central trusted agency (e.g., the central bank).
The blockchain technologies are divided into three generations, based on the complexity of the components. The first generation of blockchain was all about cryptocurrency and its exchange possibilities. The 2.0 generation focuses heavily on the use of smart contracts built using scripting language of the blockchain. The third generation of blockchain supports decentralized applications based on blockchain technologies in other previously unsupported areas like government, health, science and culture.
Blockchain technology began with Bitcoin, and many
developers around the world still consider that the main
blockchain example. Blockchain technology relies on a shared
public ledger that entire cryptocurrency networks share and
depend on. Traditional currency system participants rely on
the bank to authenticate the integrity of a ledger, but
blockchain relies on peer-to-peer network transfer thus
eliminating the need of the third parties. Today, the first
generation of blockchain technologies is mainly defined by
cryptocurrencies like Bitcoin [
Bitcoin introduced a very basic scripting language, that
allowed some form of contractual complexity. The extension
of this scripting language to handle more complex data
manipulations within blockchain came to be defined as a
second-generation blockchain technology. The second
generation is mainly represented by Ethereum. Ethereum
proposed a structure in which blockchain technology could be
used to facilitate the management of digital assets. Ethereum
offers new functionality through so-called smart contracts,
which can manage agreements between parties on the
blockchain [
Unfortunately, these blockchain technologies are known
to struggle with scaling difficulties. Additionally, neither
Ethereum nor Bitcoin is fundamentally integrable with other
decentralized currencies or platforms; meaning that in most
cases users wishing to transfer value from one platform into
another must do so through via exchange services [
The new generation blockchains come into existence with
a focus to address the issues in both Blockchain 1.0 and 2.0
via different protocols, techniques and frameworks. High
scalability, interoperability, adaptability, sustainability,
privacy as well as instantaneous transactions are features that
should separate Blockchain 3.0 from its previous iterations
[
An additional implementation of more advanced data
manipulation mechanism for blockchain enabled application
layer development in the form of smart contracts. Basically, a
smart contract is a deployed program that can be executed on
the blockchain network following the principle of trigger
causing an appropriate reaction [
The consumer deals directly with the transactions on the
blockchain, a smart contract holds value which is released at
the time certain conditions are met, this way the contracts have
lower transactional costs unlike traditional contracts [
Blockchain technologies are rapidly evolving and the area of their application broadens. Our research focusses on analyzing the applicability of these technologies in various areas and possibilities of improving the development process of blockchain-based systems.
III.
RELATED WORK
In this section we overview applications of blockchain technologies in various fields and discuss difficulties of application of blockchain technology to diverse domains. The research on the applicability of modelling techniques to blockchain-based system development is also overviewed.
One of the blockchain application areas is tracking the
provenance of assets. Solutions like supply chain management
are one of the business issues that could benefit from
automation with smart contracts. Evaluation of provenance is
generally difficult not only because of the number of goods
that are handled in complex supply chains but also because of
the amount of information for tracking product location,
physical characteristics. As a solution to this problem, simple
data models of the ontology were described. These models
were later used to develop smart contract implementation [
Another way to utilize smart contract on blockchain is insurance-related contracts. The extended solution in a form of framework exists to help developers deploy more secure and less costly contracts. Smart contracts can automate the processes of insurance operations such as client registration, policy assignment, premium payouts, submission claims, and processing of refunds without or with minimal involvement of third parties [7].
As well as business processes, there are many suggestions
to improve scientific processes using blockchain technologies
[9] [
Blockchain use cases continue to grow in scope and
complexity, that is why the need for common guidelines
becomes apparent [
The lack of a formal and unified methodology complicates
the application of blockchain technology. Only a small portion
of authors describe their development process, unfortunately
these are often specialized for specific use cases. A universal
method for development could ease the design and
implementation process of blockchain technology-based
systems [
Based on the analysis of blockchain application areas and proposed techniques for its implementation, introduction of a common methodology for blockchain-based system development could facilitate the development process and broaden the scope of its applications.
IV. APPLYING THE PRINCIPLES OF MODEL-DRIVEN ARCHITECTURE FOR BLOCKCHAIN-BASED SYSTEMS
DEVELOPMENT
To facilitate the development of a blockchain-based
system, we propose a methodology based on MDA principles.
We believe, that such methodology could help to describe
blockchain-based systems concepts and behavior in a more
general language [
In the first development stage Computation Independent Model (CIM) should be specified. The purpose of this model is to show how blockchain could be adapted for specific processes’ restructuring, reorganization, and integration. In MDA, a Computation Independent Model (CIM) is often referred to as a business or domain model. It presents the context of the system under development and what the system is expected to do but hides all information technology related specifications to remain independent. A model should be created using the provided UML profile for blockchain CIM. It would consist of a participation interaction model, vocabulary and a business case process model.
Due to the fact that blockchain technology is not
applicable in every case, solutions helping to determine the
suitability of blockchain exists [
If blockchain technology is applicable, the development of the blockchain would continue with the design of the Platform Independent Model (PIM). Traditionally PIM represents the design of the system without the details about its implementation. Considering the method is tailored for the blockchain, the defined models would include details about implementation, but would not be based on any specific blockchain technology (e.g. Hyperledger or Ethereum). The previously described CIM models would be used as an input for the development of the PIM. Using the blockchain PIM, a smart contract state model, blockchain structure model and blockchain-based process model can be defined. These defined models would help to select a specific platform for further development because different platforms differ in terms of chain architecture, transaction structure, number of participants, smart contract capabilities, consensus algorithms and so on.
Afterwards the development of blockchain Platform
Specific Model (PSM) would take place. MDA suggests
automating the production of a PSM from previously defined
models. It requires to define transformation rules which
specify how models are transformed based on parameters
defined by developers [
The proposed methodology would not only help to define the blockchain artefacts, but also help to identify whether it is reasonable to adopt the technology. It could also offer guidelines for selecting appropriate blockchain platform. The solution would provide the possibility to facilitate and at least partially automate the blockchain technology-based system development process by providing a more standardized way of describing such systems, expanding the potential uses of blockchain for different business goals by restructuring current business processes.
The blockchain technologies are currently most broadly applied in the financial sector, and the application in other areas is still quite limited. The design process of blockchain technology-based systems is quite difficult, because no formal or formalized design, development methodologies exist. A proposed application of MDA principles in the process of development of blockchain technology-based systems should help to determine whether it is possible to model blockchain structure and smart contract logic and whether the business logic could be conveyed in the smart contracts. The methodology could be used for modelling blockchain and smart contracts of business processes and thus relocating these to the blockchain. In addition, an extensive analysis of business processes is still required for determining how the relocation of the business logic to the blockchain could affect the current processes. Going forward, it is essential to thoroughly examine the possibilities of adopting MDA principles for blockchain technology-based system development process. It is important to analyze blockchain implementations and find common elements. The results should help to determine how to model blockchain structure and smart contract logic, and how business logic can be conveyed by the smart contracts.
Generalised
Available: