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ICSA, Early Career Researchers Forum
Seattle, USA
2018-05-01
Florian Weßling
florian.wessling@paluno.uni-due.de
University Duisburg-Essen, Germany
Prof. Dr. Volker Gruhn
Engineering Software Architectures of
Blockchain-Oriented Applications

Overview
• Blockchain Intro
• Architectures of Blockchain-based Applications
• Next Steps and Discussion
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Blockchain Intro

Blockchain Technology
• Goal: Saving information
• "A blockchain is a database that can be shared between a group of non-trusting
individuals, without needing a central party to maintain the state of the database."
• Avoid centralization (Server) – Trend towards decentralization (P2P)
• Save information and create consensus (distributed ledger)
• No trust necessary towards a central authority
• Trust towards a self-sustaining protocol using certain incentives to validate
transactions
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– https://medium.com/loom-network/scalability-tradeoffs-why-the-ethereum-killer-hasnt-arrived-yet-8f60a88e46c0

• Consensus about world state: values of objects
• Transactions modify the world state deterministically
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Contract 0x123
{insuranceId: 0x485,
premium: 851241,
trigger: 0x791,
setPremium: func(a) {
this.premium = a
}
} Transaction 0x8682934
To: 0x123
Call: setPremium(1500)
Contract 0x123
{insuranceId: 0x485,
premium: 1500,
trigger: 0x791,
setPremium: func(a) {
this.premium = a
}
}
Ethereum

• Each node saves the latest world state
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Transaction
0x8682934
setPremium(1500)
Node #74
Contract 0x123
{insuranceId: 0x485,
premium: 851241,
trigger: 0x791,
setPremium: func(a) }
Contract 0x815
{...}
Node #74
Contract 0x123
{insuranceId: 0x485,
premium: 851241,
trigger: 0x791,
setPremium: func(a) }
Contract 0x815
{...}
Node #74
Contract 0x123
{insuranceId: 0x485,
premium: 851241,
trigger: 0x791,
setPremium: func(a) }
Contract 0x815
{...}
Transaction
0x8682934
setPremium(1500)
Transaction
0x8682934
setPremium(1500)
Ethereum

• Receive transaction and update world state
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Node #74
Contract 0x123
{insuranceId: 0x485,
premium: 1500,
trigger: 0x791,
setPremium: func(a) }
Contract 0x815
{...}
Node #74
Contract 0x123
{insuranceId: 0x485,
premium: 1500,
trigger: 0x791,
setPremium: func(a) }
Contract 0x815
{...}
Node #74
Contract 0x123
{insuranceId: 0x485,
premium: 1500,
trigger: 0x791,
setPremium: func(a) }
Contract 0x815
{...}
Ethereum
✅
✅
✅
✅
✅
✅
✅

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Architectures of
Blockchain-based
Applications

• Increasing need for building blockchain-based applications
(decentralized apps = DApps)
• → Increasing need for good architectures and smart contracts!
• Deal with blockchain properties: decentral, trustless, transparent and immutable
system
• Best practices, architectural patterns, design patterns for smart contracts
• Main Research Question:
How to determine the architecture of a blockchain-based application?
• Concepts to support architectural design of blockchain-based applications are missing
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Research Motivation

Which architectural patterns exist in
blockchain-based applications?
• Examine architectures of existing DApps
• A: Self-Generated Transaction
• B: Self-Confirmed Transaction
• C: Delegated Transactions
• Compare pros and cons regarding costs, trust,
complexity, user experience
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Browser
MetaMask
/ Wallet
Private or Public Blockchain Node
MyEtherWallet
Blockchain
/ EDCC A
Browser
MetaMask
/ Wallet
DApp-Website
Private or Public
Blockchain
Node
Blockchain
/ EDCC B
Browser
DApp-
Website
DApp-Server/Backend
REST
Private or
Public
Blockchain
Node
DApp
Backend
Logic
Transactions
Private or
Public
Blockchain
Node
Websocket
Blockchain
/ EDCC
C
DApp Architectures
[2]

Outlook: Overall Concept
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B
ZY
S
X
Contractor
Construction
Supervisor
Building
Owner
Contractor Contractor
Area B
Area A
B
ZY
S
X
Contractor
Construction
Supervisor
Building
Owner
Contractor Contractor
B
ZY
S
X
Contractor
Construction
Supervisor
Building
Owner
Contractor Contractor
B
ZY
S
X
Contractor
Construction
Supervisor
Building
Owner
Contractor Contractor
Architectural Patterns
+ Best Practices
Use Case
Terms
+ Properties
Implementation as
Smart Contract
+ Design Patterns

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Next Steps
and
Discussion

• Risk: Ethereum technology lock-in
• start with Ethereum, extend to other platforms
• goal: generalized and technology agnostic approach
• Next Steps
• write down research questions and hypotheses
• describe the research outcome/artifacts and methodology how to get there
• Advice from ECRF mentor: Qualitative studies: (semi-)structured interviews/questionnaires
• Examine the Architecture Tradeoff Analysis Method (ATAM): look where Blockchain aspects are not covered
• Working on validation: Three research projects in submission (energy, building, insurance)
Next Steps and Discussion
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Thank you! 😄
Questions? 💭
Discussion? 💬