Software systems are not static, they have to undergo frequent changes to stay fit for purpose, and in the process of doing so, their complexity increases. It has been observed that this process often leads to the erosion of the systems design and architecture and with it, the decline of many desirable quality attributes, such as maintainability. This process can be captured in terms of antipatterns - atomic violations of widely accepted design principles. We present a visualisation that exposes the design of evolving Java programs, highlighting instances of selected antipatterns including their emergence and cancerous growth. This visualisation assists software engineers and architects in assessing, tracing and therefore combating design erosion. We evaluated the effectiveness of the visualisation in four case studies with ten participants.

1. Visualizing Design Erosion:
How Big Balls of Mud are Made
VISSOFT 2018
Madrid, 2018-09-24
David Baum, Jens Dietrich,
Craig Anslow, Richard Müller

2. Visualizing Design Erosion | VISSOFT 2018
David Baum 2
USE CASE
 Antipattern and smells are used to assess systems
design and archtitecture with static analysis
 The evolution of antipatterns is under-researched
 Trace back origin of antipattern instances
 Find versions with design erosion/quality loss
 Once you know the when you can investigate the why
 Product releases under time pressure
 Team changes
 …

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David Baum 3
ANTIPATTERN
 Cyclic Dependencies (CD)
 Subtype Knowledge (STK)
[Stevens et al., 1979]
[Riehl, 1996]

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David Baum 4
 Packages
 gray circles
 Classes
 green disks
 Nested according to
containment tree
STRUCTURE VISUALIZATION

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David Baum 5
ANTIPATTERN VISUALIZATION
 Antipattern instances can be selected for detailed view
 depedencies between classes
 Disk size indicates the
importance of the
classes for the antipattern
instance
 Biggest class is the most
central class of this anti-
pattern
 Analogous for STK, but
color (green red scale) instead
of size indicates centrality

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David Baum 6
EVOLUTION VISUALIZATION
 Visualize versions above each other
 x and y coordinates of disks are stable, so identical disks
are exactly above each other

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David Baum 7
EVALUATION
 Preliminary evaluation with 10 participants
 Which version reduced the quality of the system the
most?
 Which packages are part of the original Circular
Dependency Component 1?
 With which class would you start refactoring?
 Result: „it works“
 Participants gave reasonable answers
 Participants like the tool and find it effective for solving the
tasks
 Compairing versions was described as „very intuitive“
 No complains about occlusion

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David Baum 8
BUT ...
 Red green scale is very misleading
 Some complaints about navigation mode
 Participants asked for more context/information for
solving the tasks
 Some technical issues, mostly with X3DOM as
visualization technique
 Scalability needs to be improved

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David Baum 9
SUMMARY
 „Big Balls of Mud“ can be traced over multiple versions
to see how they emerged and evolved
 Visualizing design erosion …
 supports refactoring decisions,
 supports assessing quality of software architecture
 might be a starting point for further analysis, combining
technical and social information

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David Baum 10
References
 W. Stevens, G. Myers, and L. Constantine. 1979.
Structured design. In Classics in software engineering,
Edward Nash Yourdon (Ed.). Yourdon Press, Upper
Saddle River, NJ, USA 205-232.
 A. J. Riel. Object-Oriented Design Heuristics. Addison-
Wesley Longman Publishing Co., Inc., Boston, MA,
USA, 1996.