@book {1591,
	title = {Code Review Analytics: WebKit as Case Study},
	series = {IFIP Advances in Information and Communication TechnologyOpen Source Software: Mobile Open Source Technologies. 10th IFIP WG 2.13 International Conference on Open Source Systems, OSS 2014, San Jos{\'e}, Costa Rica, May 6-9, 2014. Proceedings},
	volume = {427},
	year = {2014},
	pages = {1 - 10},
	publisher = {Springer Berlin Heidelberg},
	organization = {Springer Berlin Heidelberg},
	address = {Berlin, Heidelberg},
	abstract = {During the last years, most of the large free / open source software projects have included code review as an usual, or even mandatory practice for changes to their code. In many cases it is implemented as a process in which a developer proposing some change needs to ask for a review by another developer before it can enter the code base. Code reviews, therefore, become a critical process for the project, which could cause delays in contributions being accepted, and risk to become a bottleneck if not enough reviewers are available. In this paper we present a methodology designed to analyze the code review process, to determine its main characteristics and parameters, and to detect potential problems with it. We also present how we have applied this methodology to the WebKit project, learning about the main characteristics of how code review works in their case.},
	isbn = {978-3-642-55128-4},
	issn = {1868-422X},
	doi = {10.1007/978-3-642-55128-4_1},
	author = {Gonz{\'a}lez-Barahona, Jes{\'u}s M. and Izquierdo-Cort{\'a}zar, Daniel and Gregorio Robles and Mario Gallegos},
	editor = {Corral, Luis and Sillitti, Alberto and Succi, Giancarlo and Vlasenko, Jelena and Wasserman, Anthony I.}
}
@conference {Robles:2014:EDE:2597073.2597107,
	title = {Estimating Development Effort in Free/Open Source Software Projects by Mining Software Repositories: A Case Study of OpenStack},
	booktitle = {Proceedings of the 11th Working Conference on Mining Software Repositories},
	series = {MSR 2014},
	year = {2014},
	pages = {222{\textendash}231},
	publisher = {ACM},
	organization = {ACM},
	address = {New York, NY, USA},
	abstract = {Because of the distributed and collaborative nature of free / open source software (FOSS) projects, the development effort invested in a project is usually unknown, even after the software has been released. However, this information is becoming of major interest, especially ---but not only--- because of the growth in the number of companies for which FOSS has become relevant for their business strategy. In this paper we present a novel approach to estimate effort by considering data from source code management repositories. We apply our model to the OpenStack project, a FOSS project with more than 1,000 authors, in which several tens of companies cooperate. Based on data from its repositories and together with the input from a survey answered by more than 100 developers, we show that the model offers a simple, but sound way of obtaining software development estimations with bounded margins of error.
},
	keywords = {effort estimation, free software, mining software repositories, open source, openstack},
	isbn = {978-1-4503-2863-0},
	doi = {10.1145/2597073.2597107},
	url = {http://doi.acm.org/10.1145/2597073.2597107},
	attachments = {https://flosshub.org/sites/flosshub.org/files/robles_0.pdf},
	author = {Gregorio Robles and Gonz{\'a}lez-Barahona, Jes{\'u}s M. and Cervig{\'o}n, Carlos and Capiluppi, Andrea and Izquierdo-Cort{\'a}zar, Daniel}
}
@proceedings {1458,
	title = {Do More Experienced Developers Introduce Fewer Bugs?},
	volume = {378},
	year = {2012},
	note = {"Some Mozilla Foundation projects have been the selected case of study for this paper. The analysis is based on the Mercurial repository which offers a list of repositories that can be easily cloned. As a summary, 19 projects were analyzed, with more than 100,000 commits, more than 2,500 authors and around 4 years of history up to June 2011."},
	month = {09/2012},
	pages = {268-273},
	publisher = {IFIP AICT,  Springer},
	abstract = {Developer experience is a common matter of study in the software maintenance and evolution research literature. However it is still not well understood if less experienced developers are more prone to introduce errors in the source code than their more experienced colleagues. This paper aims to study the relationships between experience and the bug introduction ratio using the Mozilla community as case of study.
As results, statistical differences among developers with different levels of experience has not been observed, when the expected result would have been the opposite1.},
	keywords = {mercurial, mozilla, scm, source code analysis},
	author = {Izquierdo-Cort{\'a}zar, Daniel and Gregorio Robles and Gonz{\'a}lez-Barahona, Jes{\'u}s M.}
}
@article {1418,
	title = {Effort estimation of FLOSS projects: a study of the Linux kernel},
	journal = {Empirical Software Engineering},
	year = {2011},
	pages = {1-29},
	abstract = {Empirical research on Free/Libre/Open Source Software (FLOSS) has shown that developers tend to cluster around two main roles: {\textquotedblleft}core{\textquotedblright} contributors differ from {\textquotedblleft}peripheral{\textquotedblright} developers in terms of a larger number of responsibilities and a higher productivity pattern. A further, cross-cutting characterization of developers could be achieved by associating developers with {\textquotedblleft}time slots{\textquotedblright}, and different patterns of activity and effort could be associated to such slots. Such analysis, if replicated, could be used not only to compare different FLOSS communities, and to evaluate their stability and maturity, but also to determine within projects, how the effort is distributed in a given period, and to estimate future needs with respect to key points in the software life-cycle (e.g., major releases). This study analyses the activity patterns within the Linux kernel project, at first focusing on the overall distribution of effort and activity within weeks and days; then, dividing each day into three 8-hour time slots, and focusing on effort and activity around major releases. Such analyses have the objective of evaluating effort, productivity and types of activity globally and around major releases. They enable a comparison of these releases and patterns of effort and activities with traditional software products and processes, and in turn, the identification of company-driven projects (i.e., working mainly during office hours) among FLOSS endeavors. The results of this research show that, overall, the effort within the Linux kernel community is constant (albeit at different levels) throughout the week, signalling the need of updated estimation models, different from those used in traditional 9am{\textendash}5pm, Monday to Friday commercial companies. It also becomes evident that the activity before a release is vastly different from after a release, and that the changes show an increase in code complexity in specific time slots (notably in the late night hours), which will later require additional maintenance efforts.},
	keywords = {complexity, effort estimation, Effort models, mining software repositories, open source software},
	issn = {1573-7616},
	doi = {10.1007/s10664-011-9191-7},
	url = {http://www.springerlink.com/content/612r616k8t52m867/fulltext.html},
	author = {Capiluppi, Andrea and Izquierdo-Cort{\'a}zar, Daniel}
}
@conference {599,
	title = {4th International Workshop on Public Data about Software Development},
	booktitle = {OSS2009: Open Source Ecosystems: Diverse Communities Interacting (IFIP 2.13)},
	series = {IFIP Advances in Information and Communication Technology },
	volume = {299/2009},
	year = {2009},
	month = {2009///},
	pages = {351 - 352},
	publisher = {Springer},
	organization = {Springer},
	chapter = {31},
	abstract = {Libre (free, open source) projects offer publicly available data sources. The research community is starting to produce, use and exchange large data sets of information. These data sets have to be retrieved, purged, described, and can be published for public consumption by other groups. Their availability allows for the decoupling of research activities, the reproducibility of research results, and even the collaboration (and competition) in the analysis of data. This activity is frequently presented at workshops and conferences, but since the focus of these conferences is not specific to the use of public data, discussions of techniques and experiences are not as deep and fruitful as they could be. This workshop is once again (for the fourth year in a row) such a place. We will host discussions specifically about these sorts of public data sets about software development, how they are retrieved, how they can be analyzed and mined, how they can be exchanged and extended.
},
	issn = {978-3-642-02031-5},
	doi = {http://dx.doi.org/10.1007/978-3-642-02032-2_31},
	attachments = {https://flosshub.org/sites/flosshub.org/files/4the\%20International\%20Workshop\%20on\%20Public\%20Data.pdf},
	author = {Gonz{\'a}lez-Barahona, Jes{\'u}s and Squire, Megan and Izquierdo-Cort{\'a}zar, Daniel}
}
@conference {1809,
	title = {On the Analysis of Contributions from Privileged Users in Virtual Open Communities},
	booktitle = {2009 42nd Hawaii International Conference on System Sciences},
	year = {2009},
	pages = {1 - 10},
	publisher = {IEEE},
	organization = {IEEE},
	address = {Waikoloa, Hawaii, USA},
	abstract = {Collaborative projects built around virtual communities on the Internet have gained momentum over the last decade. Nevertheless, their rapid growth rate rises some questions:which is the most effective approach to manage and organize their content creation process? Can these communities scale, controlling their projects as their size continues to grow over time? To answer these questions, we undertake a quantitative analysis of privileged users in FLOSS development projects and in Wikipedia. From our results, we conclude that the inequality level of user contributions in both types of initiatives is remarkably distinct, even though both communities present almost identical patterns regard-ing the number of distinct contributors per file (in FLOSS  projects) or per article (in Wikipedia). As a result, totally open projects like Wikipedia can effectively deal with faster growing rates, while FLOSS projects may be affected by bottlenecks on committers who play critical roles.},
	isbn = {978-0-7695-3450-3},
	doi = {10.1109/HICSS.2009.328},
	author = {Ortega, Felipe and Izquierdo-Cort{\'a}zar, Daniel and Gonz{\'a}lez-Barahona, Jes{\'u}s M. and Gregorio Robles}
}
@conference {1812,
	title = {Measuring the performance of open source development communities: The QualOSS approach},
	booktitle = {MetriKon 2009 - Praxis der Software-Messung : Tagungsband des DASMA Software Metrik Kongresses},
	year = {2009},
	abstract = {Free and Open Source Software (F/OSS) has an increasing importance for the software industry. Similar to traditional (closed) software acquisition, F/OSS acquisition requires an assessment of whether its quality is sufficient for the intended purpose, and of whether the chances of being maintained and supported in the future, as well as of keeping certain quality standards over time, are sufficiently high. The first one of these aspects is strictly product related, and can be assessed using techniques that are not specific to F/OSS. The last two aspects, however, are related to the community developing the software, and require novel approaches to be evaluated properly.
In this paper, we present an approach toward a comprehensive measurement framework for F/OSS projects, developed in the EU project QualOSS. Although this approach takes into account product quality as well as process maturity and sustainability of the underlying F/OSS community, we concentrate here on its community-related aspects. After describing our quality model and assessment techniques in some detail, we close with a description of our ongoing evaluation effort and a discussion of lessons learned.},
	url = {http://publica.fraunhofer.de/documents/N-117870.html},
	author = {Soto, Martin and Izquierdo-Cort{\'a}zar, Daniel and Ciolkowski, Marcus}
}
@article {1814,
	title = {Relationship between size, effort, duration and number of contributors in large FLOSS projects},
	journal = { 7th BElgian-NEtherlands software eVOLution workshop - BENEVOL 2008},
	year = {2008},
	abstract = {This contribution presents initial results in the study of the relationship between size,
effort, duration and number of contributors in eleven evolving Free/Libre Open Source
Software (FLOSS) projects, in the range from approx. 650,000 to 5,300,000 lines of
code. Our initial motivation was to estimate how much effort is involved in achieving
a large FLOSS system. Software cost estimation for proprietary projects has been an
active area of study for many years (e.g. [1][2][3]). However, to our knowledge, no previous
similar research has been conducted in FLOSS effort estimation. This research
can help planning the evolution of future FLOSS projects and in comparing them with
proprietary systems. Companies that are actively developing FLOSS may benefit from
such estimates [4]. Such estimates may also help to identify the productivity {\textquoteright}baseline{\textquoteright}
for evaluating improvements in process, methods and tools for FLOSS evolution},
	url = {http://oro.open.ac.uk/27317/1/},
	author = {Ramil, J.F. and Izquierdo-Cort{\'a}zar, Daniel and Mens, Tom}
}
