Paper: You Can't Control the Unfamiliar: A Study on the Relations Between Aggregation Techniques for Software Metrics
Authors: Bogdan Vasilescu, Alexander Serebrenik and Mark Van Den Brand
Session: Research Track 11 - Metrics
Kotlin Multiplatform & Compose Multiplatform - Starter kit for pragmatics
Metrics - You can't control the unfamiliar
1. Metrics are usually computed at a low level:
classes, methods, …
/ W&I / MDSE 5-10-2011 PAGE 0
2. Multitude of data values obscures a general
picture of the system maintainability
/W&I / MDSE 5-10-2011 PAGE 1
3. That we are actually interested in!
/W&I / MDSE 5-10-2011 PAGE 2
4. You Can't Control the Unfamiliar:
A Study on the Relations
Between Aggregation
Techniques for Software Metrics
Bogdan Vasilescu
Alexander Serebrenik
Mark van den Brand
5. Two kinds of aggregation
Same metrics, different Same artifact, different
artifacts metrics
/W&I / MDSE 5-10-2011 PAGE 4
6. Various techniques can be
found in the literature
Same metrics, different Traditional: mean,
artifacts median, sum, …
Econometric
inequality indices:
Gini, Theil, Hoover,
Kolm, Atkinson
/W&I / MDSE 5-10-2011 PAGE 5
7. Various techniques can be
found in the literature
Same metrics, different Traditional: mean,
artifacts median, sum, …
Which
aggregation
Econometric
technique
inequality indices:
Gini, Theil, Hoover,
should we
Kolm, Atkinson
use?
/W&I / MDSE 5-10-2011 PAGE 6
8. Questions
1. Which and to what extent do the different
aggregation techniques agree?
2. What is the nature of the relation between the
various aggregation techniques?
3. How does the correlation coefficient change as the
systems evolve?
/W&I / MDSE 5-10-2011 PAGE 7
9. Qualitas Corpus 20101126
• Qualitas Corpus 20101126r, 106 systems
• FitJava v1.1, 2 packages, 2240 SLOC
• NetBeans v6.9.1, 3373 packages 1890536 SLOC.
/W&I / MDSE 5-10-2011 PAGE 8
10. 1) Agreement between diff techniques
• Agreement:
• Aggregation: Class SLOC Package
• Techniques agree if they rank the packages similarly
We use rank-based correlation coefficient: Kendall’s
/W&I / MDSE 5-10-2011 PAGE 9
11. 1) Agreement: different inequality indices?
• Gini, Theil, Hoover, Atkinson – agree
• aggregates obtained convey the same information
• Kolm does not!
/W&I / MDSE 5-10-2011 PAGE 10
12. 1) Agreement: traditional and ineq indices?
• mean
• Kolm: strong (0,8) and statistically significant (92%)
• median, standard deviation, and variance
• sum
• does not correlate with any other aggregation technique
/W&I / MDSE 5-10-2011 PAGE 11
13. 2) Nature of the relation: Typical patterns
• Theil is known to be more • Linear relation with a “fat”
sensitive to the rich head
• Theil increases faster
when Gini increases
/W&I / MDSE 5-10-2011 PAGE 12
14. Which aggregation technique? (1)
• Theil, Hoover, Gini and Atkinson agree
• Any can be chosen from the correlation point of view
• Some might be “better” in each specific case
• easy to interpret: Gini [0,1]
• provide additional insights: Theil (explanation)
• negative values: Gini, Hoover
− affects the domain!
• sensitive for high values: Theil, Atkinson
• deviations from uniformity: Gini, Hoover
/ W&I / MDSE 5-10-2011 PAGE 13
15. Which aggregation technique? (2)
• Kolm and mean agree
• Kolm is reliable for skewed distributions
− better alternative (“by no means”)
• Not in the paper:
− agreement observed for NOC
− but not for DIT!
/ W&I / MDSE 5-10-2011 PAGE 14