@conference {FHL15,
	title = {Impact of Version History Metrics on Maintainability},
	booktitle = {Proceedings of the 8th International Conference on Advanced Software Engineering \& Its Applications (ASEA 2015)},
	year = {2015},
	pages = {30{\textendash}35},
	publisher = {IEEE Computer Society},
	organization = {IEEE Computer Society},
	address = {Jeju Island, Korea},
	abstract = {In this study we present how some version control history based metrics affect maintainability of the source code. These metrics cover intensity of modifications, code ownership and code aging. We determine the order of source files based on each analyzed metrics, and compare it with their maintainability based order. As a cross-check we perform a comparison test with post-release defects as well. We performed the analysis on 14 versions of 4 well-known open source software systems. The results show high correlation between the version control metrics and relative maintainability indexes, in each case. The comparison with post-release defects also support the results in most of the cases.},
	keywords = {code aging, code churn, Code ownership, Source code maintainability, version control history metrics},
	doi = {10.1109/ASEA.2015.14},
	url = {http://ieeexplore.ieee.org/document/7433065/},
	author = {Farag{\'o}, Csaba and P Heged{\H u}s and Lad{\'a}nyi, Gergely and Rudolf Ferenc}
}
@conference {LTF15,
	title = {A Software Quality Model for {RPG}},
	booktitle = {Proceedings of the 22nd IEEE International Conference on Software Analysis, Evolution, and Reengineering (SANER 2015)},
	year = {2015},
	month = {mar},
	pages = {91{\textendash}100},
	publisher = {IEEE Computer Society},
	organization = {IEEE Computer Society},
	address = {Montr{\'e}al, Canada},
	abstract = {The IBM i mainframe was designed to manage business applications for which the reliability and quality is a matter of national security. The RPG programming language is the most frequently used one on this platform. The maintainability of the source code has big influence on the development costs, probably this is the reason why it is one of the most attractive, observed and evaluated quality characteristic of all. For improving or at least preserving the maintainability level of software it is necessary to evaluate it regularly. In this study we present a quality model based on the ISO/IEC 25010 international standard for evaluating the maintainability of software systems written in RPG. As an evaluation step of the quality model we show a case study in which we explain how we integrated the quality model as a continuous quality monitoring tool into the business processes of a mid-size software company which has more than twenty years of experience in developing RPG applications.},
	keywords = {Case Study, IBM i mainframe, ISO/IEC 25010, RPG quality model, Software maintainability},
	doi = {10.1109/SANER.2015.7081819},
	url = {http://ieeexplore.ieee.org/document/7081819/},
	author = {Lad{\'a}nyi, Gergely and T{\'o}th, Zolt{\'a}n and Rudolf Ferenc and Keresztesi, Tibor}
}
@conference {LHF14,
	title = {The Connection of the Bug Density and Maintainability of Classes},
	booktitle = {8th International Workshop on Software Quality and Maintainability},
	series = {SQM},
	year = {2014},
	note = {Presentation only},
	month = {feb},
	address = {Antwerp, Belgium},
	abstract = {Measuring software product maintainability is a central issue in software engineering which led to a number of different practical quality models. Besides system level assessments it is also desirable that these models provide technical quality information at source code element level (e.g. classes, methods) to aid the improvement of the software. Although many existing models give an ordered list of source code elements that should be improved, it is unclear how these improvements affect other important quality indicators of the system, e.g. bug density. In this paper we empirically investigate the connection of bug numbers in the classes of different open-source systems and the class level maintainability measures of our ColumbusQM probabilistic quality model using open-access bug datasets. We show that classes with lower maintainability score contain significantly more bugs than more maintainable classes. Moreover, in terms of correctness and completeness, ColumbusQM competes with statistical and machine learning prediction models especially trained on the bug data using product metrics as predictors. This is a great achievement in the light of that our model needs no training and its purpose is different (e.g. to estimate testability, or development costs) than those of the bug prediction models. In summary, we show that improving the maintainability of a software according to the suggestions of our quality model will expectedly also reduce its bug density.},
	keywords = {Bug density, Bug prediction, Class level maintainability, ColumbusQM, ISO/IEC 25010, Software maintainability},
	author = {Lad{\'a}nyi, Gergely and P Heged{\H u}s and Rudolf Ferenc and Istv{\'a}n Siket and Tibor Gyim{\'o}thy}
}
@conference {BHS14,
	title = {{QualityGate SourceAudit}: a Tool for Assessing the Technical Quality of Software},
	booktitle = {Proceedings of the 2014 Software Evolution Week (Merger of the 18th IEEE European Conference on Software Maintenance and Reengineering \& 21st IEEE Working Conference on Reverse Engineering {\textendash} CSMR-WCRE 2014)},
	year = {2014},
	month = {feb},
	pages = {440{\textendash}445},
	publisher = {IEEE Computer Society},
	organization = {IEEE Computer Society},
	address = {Antwerp, Belgium},
	abstract = {Software systems are evolving continuously in order to fulfill the ever-changing business needs. This endless modification, however, decreases the internal quality of the system over time. This phenomena is called software erosion, which results in higher development, testing, and operational costs. The SourceAudit tool presented in this paper helps managing the technical risks of software deterioration by allowing imme-diate, automatic, and objective assessment of software quality. By monitoring the high-level technical quality of systems it is possible to immediately perform the necessary steps needed to reduce the effects of software erosion, thus reaching higher maintainability and lower costs in the mid and long-term. The tool measures source code maintainability according to the ISO/IEC 25010 based probabilistic software maintainability model called ColumbusQM. It gives a holistic view on software quality and warns on source code maintainability decline.},
	keywords = {ColumbusQM, development costs, internal system quality, ISO-IEC 25010 based probabilistic software maintainability, operational costs, QualityGate SourceAudit, software deterioration, Software Erosion, Source code maintainability, technical software quality, testing costs},
	doi = {10.1109/CSMR-WCRE.2014.6747214},
	url = {http://ieeexplore.ieee.org/document/6747214/},
	author = {Tibor Bakota and P Heged{\H u}s and Istv{\'a}n Siket and Lad{\'a}nyi, Gergely 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}
}
