@article {FHV14,
	title = {Connection Between Version Control Operations and Quality Change of the Source Code},
	journal = {Acta Cybernetica},
	volume = {21},
	number = {4},
	year = {2014},
	pages = {585{\textendash}607},
	abstract = {Software erosion is a well-known phenomena, meaning that software quality is continuously decreasing due to the ever-ongoing modifications in the source code. In this research work we investigated this phenomena by studying the impact of version control commit operations (add, update, delete) on the quality of the code. We calculated the ISO/IEC 9126 quality attributes for thousands of revisions of an industrial and three open-source software systems with the help of the Columbus Quality Model. We also collected the cardinality of each version control operation type for every investigated revision. We performed Chisquared tests on contingency tables with rows of quality change and columns of version control operation commit types. We compared the results with random data as well. We identified that the relationship between the version control operations and quality change is quite strong. Great maintainability improvements are mostly caused by commits containing Add operation. Commits containing file updates only tend to have a negative impact on the quality. Deletions have a weak connection with quality, and we could not formulate a general statement.},
	keywords = {Case Study, ISO/IEC 9126, Software Erosion, Software maintainability, Source Code Version Control},
	issn = {0324-721X},
	url = {http://publicatio.bibl.u-szeged.hu/8394/},
	author = {Farag{\'o}, Csaba and P Heged{\H u}s and V{\'e}gh, {\'A}d{\'a}m Zolt{\'a}n and Rudolf Ferenc}
}
@conference {FHF14,
	title = {The Impact of Version Control Operations on the Quality Change of the Source Code},
	booktitle = {Proceedings of the 14th International Conference on Computational Science and Its Applications (ICCSA 2014)},
	series = {Lecture Notes in Computer Science (LNCS)},
	volume = {8583},
	year = {2014},
	month = {jun},
	pages = {353{\textendash}369},
	publisher = {Springer-Verlag},
	organization = {Springer-Verlag},
	address = {Guimar{\~a}es, Portugal},
	abstract = {The number of software systems under development and maintenance is rapidly increasing. The quality of a system{\textquoteright}s source code tends to decrease during its lifetime which is a problem because maintaining low quality code consumes a big portion of the available efforts. In this research we investigated one aspect of code change, the version control commit operations (add, update, delete). We studied the impact of these operations on the maintainability of the code. We calculated the ISO/IEC 9126 quality attributes for thousands of revisions of an industrial and three open-source software systems. We also collected the cardinality of each version control operation type for every investigated revision. Based on these data, we identified that operation Add has a rather positive, while operation Update has a rather negative effect on the quality. On the other hand, for operation Delete we could not find a clear connection to quality change.},
	keywords = {Case Study, ISO/IEC 9126, Software Erosion, Software maintainability, Source Code Version Control},
	doi = {10.1007/978-3-319-09156-3_26},
	url = {https://link.springer.com/chapter/10.1007\%2F978-3-319-09156-3_26},
	author = {Farag{\'o}, Csaba and P Heged{\H u}s and Rudolf Ferenc}
}
@article {HBL13,
	title = {A Drill-Down Approach for Measuring Maintainability at Source Code Element Level},
	journal = {Electronic Communications of the {EASST}},
	volume = {60},
	year = {2013},
	pages = {1{\textendash}21},
	abstract = {Measuring source code maintainability has always been a challenge for software engineers. To address this problem, a number of metrics-based quality models have been proposed by researchers. Besides expressing source code maintainability in terms of numerical values, these models are also expected to provide explicable results, i.e. to give a detailed list of source code fragments that should be improved in order to reach higher overall quality. In this paper, we propose a general method for drilling down to the root causes of a quality rating. According to our approach, a relative maintainability index can be calculated for each source code element for which metrics are calculated (e.g. methods, classes). The index value expresses the source code element{\textquoteright}s contribution to the overall quality rating. We empirically validated the method on the jEdit open source tool, by comparing the results with the opinions of software engineering students. The case study shows that there is a high, 0.68 Spearman{\textquoteright}s correlation, which suggests that relative maintainability indices assigned by our method express the subjective feelings of humans fairly well.},
	keywords = {ISO/IEC 9126, Method level maintainability, Metrics-based quality model, Relative maintainability index},
	issn = {1863-2122},
	doi = {10.14279/tuj.eceasst.60.852},
	url = {https://journal.ub.tu-berlin.de/eceasst/article/view/852},
	author = {P Heged{\H u}s and Tibor Bakota and Lad{\'a}nyi, Gergely and Farag{\'o}, Csaba and Rudolf Ferenc}
}
@conference {HBL13b,
	title = {A Drill-Down Approach for Measuring Maintainability at Source Code Element Level},
	booktitle = {Proceedings of the 7th International Workshop on Software Quality and Maintainability (SQM 2013)},
	year = {2013},
	month = {mar},
	pages = {20{\textendash}29},
	address = {Genova, Italy},
	abstract = {Measuring source code maintainability has always been a challenge for software engineers. To address this problem, a number of metrics-based quality models have been proposed by researchers. Besides expressing source code maintainability in terms of numerical values, these models are also expected to provide explicable results, i.e. to give a detailed list of source code fragments that should be improved in order to reach higher overall quality. In this paper, we propose a general method for drilling down to the root causes of a quality rating. According to our approach, a relative maintainability index can be calculated for each source code element for which metrics are calculated (e.g. methods, classes). The index value expresses the source code element{\textquoteright}s contribution to the overall quality rating. We empirically validated the method on the jEdit open source tool, by comparing the results with the opinions of software engineering students. The case study shows that there is a high, 0.68 Spearman{\textquoteright}s correlation, which suggests that relative maintainability indices assigned by our method express the subjective feelings of humans fairly well.},
	keywords = {ISO/IEC 9126, Method level maintainability, Metrics-based quality model, Relative maintainability index},
	author = {P Heged{\H u}s and Tibor Bakota and Lad{\'a}nyi, Gergely and Farag{\'o}, Csaba and Rudolf Ferenc}
}
