Multi-layer software configuration: Empirical study on wordpress

Software can be adapted to different situations and platforms by changing its configuration. However, incorrect configurations can lead to configuration errors that are hard to resolve or understand, especially in the case of multi-layer architectures, where configuration options in each layer might contradict each other or be hard to trace to each other. Hence, this paper performs an empirical study on the occurrence of multi-layer configuration options across Wordpress (WP) plugins, WP, and the PHP engine. Our analyses show that WP and its plugins use on average 76 configuration options, a number that increases across time. We also find that each plugin uses on average 1.49% to 9.49% of all WP database options, and 1.38% to 15.18% of all WP configurable constants. 85.16% of all WP database options, 78.88% of all WP configurable constants, and 52 PHP configuration options are used by at least two plugins at the same time. Finally, we show how the latter options have a larger potential for questions and confusion amongst users.