AbstractOver the past decade, research has explored managing the availability of shared personal online data, with particular focus on longitudinal aspects of privacy. Yet, there is no taxonomy that takes user perspective and technical approaches into account. In this work, we systematize research on longitudinal privacy management of publicly shared personal online data from these two perspectives: user studies capturing users' interactions related to the availability of their online data and

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... echnical proposals limiting the availability of data. Following a systematic approach, we derive conflicts between these two sides that have not yet been addressed appropriately, resulting in a list of challenging open problems to be tackled by future research. While limitations of data availability in proposed approaches and real systems are mostly time-based, users' desired models are rather complex, taking into account content, audience, and the context in which data has been shared. Our systematic evaluation reveals interesting challenges broadly categorized by expiration conditions, data co-ownership, user awareness, and security and trust.