1. 1
WETSEB @ ICSE 2018
Gothenburg, Sweden
2018-05-27
Florian Wessling, Christopher Ehmke, Marc Hesenius and Volker Gruhn
florian.wessling@paluno.uni-due.de
University Duisburg-Essen, Germany
Prof. Dr. Volker Gruhn
How Much Blockchain Do You Need?
Towards a Concept for Building
Hybrid DApp Architectures

2. Motivation
• Take advantage of Blockchain technology:
decentralized, trustless, transparent and tamper-proof app environment
• Deal with disadvantages:
blocktime delay, technical complexity, difficult updates
• Difficult to determine:
• Which attributes are important for my use case?
• Which elements of my architecture benefit from blockchain technology?
• Increasing need to build good decentralized app (DApp) architectures
• Best practices, architectural patterns, design patterns for smart contracts
• Concepts to support architectural design of blockchain-based applications are missing
2

3. Current Approaches
3
• No
• Yes, Public
• Yes, Private
Do I need a Blockchain?
• Yes, 1.2 MB Blocksize,
13s Blocktime, Hybrid
PoS/PoW consensus, ...
• Yes, custom protocol,
9.4s Blocktime, DPoS
consensus, ...
Gap: Finer-grained and balanced approach!

4. • Four step approach:
• 1. Identify participants
• 2. Identify trust relations between participants
• 3. Identify interactions between participants
• 4. Derive an architectural draft
• Usage
• Adding blockchain technology to existing systems
• Assessing use cases for implementing a new system
4
B
ZY
S
X
Contractor
Construction
Supervisor
Building
Owner
Contractor Contractor
1. Participants
B
ZY
S
X
Contractor
Construction
Supervisor
Building
Owner
Contractor Contractor
2. Trust Relations
B
ZY
S
X
Contractor
Construction
Supervisor
Building
Owner
Contractor Contractor
3. Interactions
Area B
Area A
B
ZY
S
X
Contractor
Construction
Supervisor
Building
Owner
Contractor Contractor
4. Architectural Draft
[2]

5. • Example use case: Coordination and payment of craftsmen constructing a building
• 1. Identify participants
• 2. Identify trust relations between participants
• Building owner and construction supervisor trust each other
• Contractors only trust supervisor as their only contact with the construction site
• 3. Identify interactions between participants
• Contractors report to supervisor
• Supervisor reports to building owner
• Building owner pays contractors
• 4. Derive an architectural draft
• Use of blockchain technology in Area A makes no sense
• For interaction between Building Owner and Contractors using a blockchain makes sense!
5
B
ZY
S
X
Contractor
Construction
Supervisor
Building
Owner
Contractor Contractor
1. Participants
B
ZY
S
X
Contractor
Construction
Supervisor
Building
Owner
Contractor Contractor
2. Trust Relations
B
ZY
S
X
Contractor
Construction
Supervisor
Building
Owner
Contractor Contractor
3. Interactions
Area B
Area A
B
ZY
S
X
Contractor
Construction
Supervisor
Building
Owner
Contractor Contractor
4. Architectural Draft
[2]

6. Outlook: Overall Concept
6
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

7. • Open issues
• How to model trust? Different levels of trust? Depending on context?
• How to model interactions? What is the right level of abstraction? Which interactions are relevant?
• Clear terminology for terms is required
• Validation
• Small-scale study with group of 8 students (CS Master)
• Build architectures within research projects (building, energy, insurance)
• How to quantify the results? How to measure what a good architecture is?
Future Work
7

8. 8
Thank you! 😄
Questions? 💭
Discussion? 💬