Measuring Disruption from Software

Evolution Activities Using Graph-

Based Metrics

Prashant Paymal, Rajvardhan Patil, Sanjukta Bhowmick, Harvey Siy

Department of Computer Science,

University of Nebraska at Omaha

Introduction

• Real world software systems have large numbers of components (e.g. classes, functions, etc.)

• It is difficult to get a quick summary of how system evolved after a major change such as perfective maintenance activity or new software release

Case Study

• Our case study consists of six versions of JHotDraw from March 2001 to January 2004

Version Date Commit Messages

V1 3/9/2001 Merge to JHotDraw 5.2 (using JFC/Swing GUI components)

V2 10/24/2001 Before merge for version 5.3 (dnd, undo…) merge dnd(before 5.3)

V3 8/4/2002 After various merges… (before 5.4 relaease)

V4 11/8/2002 Refactor to use StandardStorageFormat as a superclass

V5 5/8/2003 Refactoring of Cursor. – java.awt.Cursor(class) has been systematically replaced

V6 1/9/2004 After renaming the CH.ifa.draw to org.jhotdraw

Network Construction

• Extracted relationships from these versions (inheritance, implementation, method calls and class member access, object declaration and instantiation)

• Network was created by connecting class dependencies, where each edge (u, v) is a dependency from class „u‟ to class „v‟

Vertex Properties

• Degree Distribution ▫ Frequency of vertices per degree, scale

free for most real world networks

• Clustering Coefficient ▫ Connections between neighbors

• Betweenness Centrality▫ Ratio of shortest paths through a

vertex

• Articulation Points▫ It‟s removal would cause the network to

become disconnected

• Network representing Version 1,▫ Lighter Nodes: High Betweenness Centrality▫ Larger Nodes: High Clustering Coefficient

Objective

• Extract key combinatorial properties from these six networks that would enable us to detect evolutionary characteristics such as

▫ Points of significant change in the software

▫ How these changes affect crucial classes in the network

Change in Vertex Properties

• All properties increased with version number

Correlation Between Properties

▫ Positive correlation between degree and betweenness centrality

▫ Correlation between clustering coefficient and betweenness centrality changes across versions

Disruption in Values and Rank

• We examine how the relationships between these properties changed from one version to the next

Disruption in Values and Rank

Disruption in Values and Rank

Identifying Crucial Vertices

• High▫ If vertex has high rank (within top 25) in at least one of the

following categories• Extra High

▫ If vertex has high rank in at least two categories• Low

▫ If vertex has zero value for any one vertex based properties and is not marked as a High vertex

• Extra Low▫ If it has zero value for both betweenness centrality and

clustering coefficient

• (High Betweenness Centrality, High Indegree, High Outdegree, High Clustering Coefficient / Articulation Point)

Percentage Breakdown of All Vertices

in Each Version

Percentage Breakdown of Vertices

(Common to All Versions)

High

Extra High

Low

Extra Low

Other

Analysis of Newly Added Vertices

Bug Frequencies

• Changes that have the keywords “bug fix” in the change log

• The periods with high percentage are also the periods after the high disruption

Conclusion

• The significant evolutionary changes occur between Version 2 – Version 3 and Version 4 – Version 5

• The network has grown cumulatively. Newer vertices tend to get added to the peripheries of the network

• The top 25 ranking of vertices was generally stable across versions. Important nodes stay important. This indicates stability in the design.

• The bug frequency is higher after Version 3 and Version 5. The degree of disruption can help explain why bug incidence increases (future work)

Acknowledgement

• Nebraska EPSCoR

• College of IS&T, University of Nebraska at Omaha

Thank you!