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From Igor Wiese <igor.wi...@gmail.com>
Subject Information from Derby Community
Date Mon, 14 Dec 2015 22:59:33 GMT
Hi, Derby Community.

My name is Igor Wiese, phd Student from Brazil. I sent an email a week
ago about my research. We received some visit to inspect the results
but any feedback was provided.

I am investigating two important questions: What makes two files
change together? Can we predict when they are going to co-change
again?


I've tried to investigate this question on the Derby project. I've
collected data from issue reports, discussions and commits and using
some machine learning techniques to build a prediction model.


I collected a total of 5266 commits in which a pair of files changed
together and could correctly predict 86% commits. These were the most
useful information for predicting co-changes of files:

- number of lines of code added,

- number of lines of code removed,

- sum of number of lines of code added, modified and removed,

- number of words used to describe and discuss the issues, and

- median value of closeness, a social network measure obtained from
issue comments.


To illustrate, consider the following example from our analysis. For
release 10.10, the files "sql/catalog/DataDictionaryImpl.java" and
"impl/storeless/EmptyDictionary.java" changed together in 7 commits.
In another 4 commits, only the first file changed, but not the second.
Collecting contextual information for each commit made to first file
in the previous release, we were able to predict all 7 commits in
which both files changed together in release 10.10, and we only issued
2 wrong predictions. For this pair of files, the most important
contextual information was the number of lines of code added, removed
and modified in each commit, and a social network measure (constraint)
obtained from issue comments.


- Do these results surprise you? Can you think in any explanation for
the results?

- Do you think that our rate of prediction is good enough to be used
for building tool support for the software community?

- Do you have any suggestion on what can be done to improve the change
recommendation?


You can visit our webpage to inspect the results in details:
http://flosscoach.com/index.php/17-cochanges/69-derby


All the best,
Igor Wiese

Phd Candidate


-- 
=================================
Igor Scaliante Wiese
PhD Candidate - Computer Science @ IME/USP
Faculty in Dept. of Computing at Universidade Tecnológica Federal do Paraná

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