Developing S-Shaped Reliability Growth Model for Open Source Software by Considering Change-Point

V.B. Singh, P.K. Kapur, and R. Kumar (India)


Open source software (OSS), reliability assessment, software reliability growth model, bug tracking system, change-point.


A paradigm shift has taken place in the field of software development during the last decade due to the advancement in the computer networks and internet technologies. Today, we are moving from closed source, i.e. proprietary software to an era of concurrent distributed development environment called open source software. During our study on various open source software development websites and literature, we observe: (i) more instructions execution and code coverage taking place with respect to time, (ii) release early, release often (iii) frequent addition of patches (iv) heterogeneity in fault density and effort expenditure (v) frequent release activities seem to have changed the bug dynamics significantly (vi) Bug reporting on bug tracking system drastically increases and decreases. Due to this the bug reported on bug tracking system keeps an irregular state and fluctuations. In open source software fault detection/removal process can not be smooth and may be changed at some time point called change-point due to varying nature of bug reporting on bug tracking system and frequent releases. When we plotted cumulative number of faults over time, most of the reliability growth curves are represented by either concave or the S-shaped. In this paper, an S-shaped software reliability growth model has been developed by considering number of instruction executed and change point in order to cater to the diverse and huge user profile, irregular state of bug tracking system and heterogeneity in fault distribution. Moreover, we have analyzed actual software failure count data to show numerical examples of software reliability assessment for the OSS.

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