Due to the rapid growth in the number of mobile applications (apps) in the past few years, succeeding in mobile app markets has become ruthless. Online app markets, such as Google Play Store, let users rate apps on a five-star scale and leave feedback. Given the importance of high star-ratings to the success of an app, it is crucial to help developers find the key topics of user-reviews that are significantly related to star-ratings of a given category. Having considered the key topics of user-reviews, app developers can narrow down their effort to the user-reviews that matter to be addressed for receiving higher star-ratings. We study 4,193,549 user-reviews of 623 Android apps that were collected from Google Play Store in ten different categories. The results show that few key topics commonly exist across categories, and each category has a specific set of key topics. We also evaluated the identified key topics with respect to the changes that are made to each version of the apps for 19 months. We observed, for 77 percent of the apps, considering the key topics in the next versions shares a significant relationship with increases in star-ratings.

GitHub facilitates software development practices that encourage collaboration and communication. Part of GitHub's model includes forking, which enables users to make changes on a copy of the base repository. The process of forking opens avenues of communication between the users from the base repository and the users from the forked repositories. Since forking on GitHub is a common mechanism for initiating repositories, we are interested in how communication between a repository and its forks (forming a software family) relates to stars. In this paper, we study communications within 385 software families comprised of 13,431 software repositories. We find that the fork depth, the number of users who have contributed to multiple repositories in the same family, the number of followers from outside the family, familial pull requests, and reported issues share a statistically significant relationship with repository stars. Due to the importance of issues and pull requests, we identify and compare common topics in issues and pull requests from inside the repository (via branching) and within the family (via forking). Our results offer insights into the importance of communication within a software family, and how this leads to higher individual repository star counts.

When a user looks for an Android app in Google Play Store, a number of apps appear in a specific rank. Mobile apps with higher ranks are more likely to be noticed and downloaded by users. The goal of this work is to understand the evolution of ranks and identify the variables that share a strong relationship with ranks. We explore 900 apps with a total of 4,878,011 user-reviews in 30 app development areas. We discover 13 clusters of rank trends. We observe that the majority of the subject apps (i.e., 61%) dropped in the rankings over the two years of our study. By applying a regression model, we find the variables that statistically significantly explain the rank trends, such as the number of releases. Moreover, we build a mixed effects model to study the changes in ranks across apps and various versions of each app. We find that not all the variables that common-wisdom would deem important have a significant relationship with ranks. Furthermore, app developers should not be afraid of a late entry into the market as new apps can achieve higher ranks than existing apps. Finally, we present the findings to 51 developers. According to the feedback, the findings can help app developers to achieve better ranks in Google Play Store.

The number of mobile apps and the number of mobile devices have increased considerably in the past few years. To succeed in the competitive market of mobile apps, such as Google Play Store, developers should improve the user-perceived quality of their apps. In this paper, we investigate the relationship between mobile device attributes and the user-perceived quality of Android apps. We observe that the user-perceived quality of apps varies across devices. Device attributes, such as the CPU and the screen resolution, share a significant relationship with the user-perceived quality. However, having a better characteristic of an attribute, such as a higher display resolution, does not necessarily share a positive relationship with the user-perceived quality. App developers should not only consider the app attributes but also consider the device attributes of the available devices to deliver high-quality apps. The original paper is published in the Empirical Software Engineering journal communicated by Lin Tan.