<p>    </p> <p>Social Media Platforms (SMPs) are used by almost 60% of the global population. Along with the ubiquity of SMPs, there are increasing Trust & Safety (T&S) risks that expose users to spam, harassment, abuse, and other harmful content online. <em>T&S Engineering </em>is an emerging area of software engineering striving to mitigate these risks. This study provides the first step in understanding this form of software engineering.</p> <p>This study examines how T&S Engineering is practiced by SMP engineers. I studied two open-source (OSS) SMPs, Mastodon and Diaspora, which comprise 89% of the 9.6 million OSS SMP accounts. I focused on the T&S design process by analyzing T&S discussions within 60 GitHub issues. I applied a T&S discussion model to taxonomize the T&S risks, T&S engineering patterns, and resolution rationales. I found that T&S issues persist throughout a platform’s lifetime, they are difficult to resolve, and engineers favor reactive treatments. To integrate findings, I mapped T&S engineering patterns onto a gen- eral model of SMPs. My findings give T&S engineers a systematic understanding of their T&S risk treatment options. I conclude with future directions to study and improve T&S Engineering, spanning software design, decision-making, and validation. </p>

A deficient safety culture has been implicated in a number of organisational accidents from a range of high hazard industries. Despite its implications for safety, many questions about safety culture remain unanswered. In order to contribute to the literature on this topic, this thesis set out to investigate the role of trust in safety culture. The oil and gas industry was chosen as the context for study due to the hazardous nature of its work, the industry’s focus on continuous improvement in safety performance and the interest shown by oil companies in participating in safety research. Leading models of safety culture have stressed the importance of trust in developing and maintaining patterns of safe behaviours at work. This thesis proposed a new model of safety culture based on dual attitudes about trust. This model states that explicit attitudes about trust are part of safety climate and that implicit attitudes about trust comprise some of the basic underlying assumptions that are the deepest level of safety culture. In order to test this model, this thesis developed a method to measure implicit attitudes about trust in an industrial setting. Using this method, two studies of dual attitudes about trust were conducted at different UK gas plants. In both of these studies, different patterns of results were found for measures of explicit and implicit attitudes about trust for workmates, supervisors and the plant leadership, respectively. These findings support the proposed model suggest that explicit and implicit attitudes about trust are separate constructs that may influence different types of safety behaviours.  Positive relationships were found between measures of explicit attitudes about trust and self-report items about safety behaviours like reporting incidents and challenging unsafe acts.  These findings were taken as a step toward validating the proposed model.