The relation relation between technical debt and corrective maintenance in PHP web applications

Context: Technical Debt Management (TDM) refers to activities that are performed to prevent the accumulation of Technical Debt (TD) in software. The state-of-research on TDM lacks empirical evidence on the relationship between the amount of TD in a software module and the interest that it accumulates. Considering the fact that in the last years, a large portion of software applications are deployed in the web, we focus this study on PHP applications. Objective: Although the relation between debt amount and interest is well-defined in traditional economics (i.e., interest is proportional to the amount of debt), this relation has not yet been explored in the context of TD. To this end, the aim of this study is to investigate the relation between the amount of TD and the interest that has to be paid during corrective maintenance. Method: To explore this relation, we performed a case study on 10 open source PHP projects. The obtained data have been analyzed to assess the relation between the amount of TD and two aspects of interest: (a) corrective maintenance (i.e., bug fixing) frequency, which translates to interest probability and (b) corrective maintenance effort which is related to interest amount. Results: Both interest probability and interest amount are positively related with the amount of TD accumulated in a specific module. Moreover, the amount of TD is able to discriminate modules that are in need of heavy corrective maintenance. Conclusions: The results of the study confirm the cornerstone of TD research, which suggests that modules with a higher level of incurred TD, are costlier in maintenance activities. In particular, such modules prove to be more defect-prone and consequently require more (corrective) maintenance effort. (C) 2017 Elsevier B.V. All rights reserved.