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From Igor Wiese <igor.wi...@gmail.com>
Subject Re: Information from Derby Community
Date Tue, 15 Dec 2015 03:26:28 GMT
Hi Rick. Now I received :-)

For sure, your explanation was very useful :-).

But, in a general case?
(http://flosscoach.com/index.php/17-cochanges/69-derby) Let's consider
that any both files changed some times together, and in some other
issues they didn't change together. We can predict 86% (in derby
project) of this changes using metrics from issues, lines of codes and
developers communication.

As a developer the normal "way" to find files to change together to
complete an issue is based on our own experience, debugging or through
the documentation, right?

What do you think? Considering these aspects, are you suprised?

Do you think that our approach could be useful for developers
(newcomers, committers, code reviewers, testers)

All the best,
Many thanks!
Igor Wiese

2015-12-14 23:21 GMT-02:00 Rick Hillegas <rick.hillegas@gmail.com>:
> Hi Igor,
> I sent the following response to your first request for feedback. I don't
> know why you didn't receive my response. Here it is again...
> ---------
> These results do not surprise me. That is because DataDictionaryImpl and
> EmptyDictionary are both implementions of the DataDictionary interface. This
> is what happens during development:
> 1) Someone wants to add a language feature which requires new metadata
> capabilities.
> 2) The new capabilities are added to the real catalog implementation, which
> is DataDictionaryImpl.
> 3) In order to use the new capabilities, they must be exposed to other Derby
> components by having corresponding methods added to the DataDictionary
> interface.
> 4) That, in turn, forces the developer to add a vacuous stub method to
> EmptyDictionary.
> I don't know if anyone uses the EmptyDictionary. At this point, it may be
> nothing more than a tax which has to be paid every time someone touches the
> data dictionary. EmptyDictionary is part of the storeless implementation of
> Derby which was apparently introduced in order to let people use the Derby
> parser to validate SQL syntax without actually running queries. That, at
> least, is the motivation described by
> http://mail-archives.apache.org/mod_mbox/db-derby-user/200612.mbox/%3C45704D0E.9030102@apache.org%3E
> and https://issues.apache.org/jira/browse/DERBY-2164. There are other
> solutions to that problem which have received more uptake in the community.
> See, for instance, https://issues.apache.org/jira/browse/DERBY-3946
> Hope this explanation is useful,
> -Rick
> On 12/14/15 2:59 PM, Igor Wiese wrote:
>> 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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