  Divisiveness appears to be increasing in much of the world, leading to
concern about political violence and a decreasing capacity to collaboratively
address large-scale societal challenges. In this working paper we aim to
articulate an interdisciplinary research and practice area focused on what we
call bridging systems: systems which increase mutual understanding and trust
across divides, creating space for productive conflict, deliberation, or
cooperation. We give examples of bridging systems across three domains:
recommender systems on social media, collective response systems, and
human-facilitated group deliberation. We argue that these examples can be more
meaningfully understood as processes for attention-allocation (as opposed to
"content distribution" or "amplification") and develop a corresponding
framework to explore similarities - and opportunities for bridging - across
these seemingly disparate domains. We focus particularly on the potential of
bridging-based ranking to bring the benefits of offline bridging into spaces
which are already governed by algorithms. Throughout, we suggest research
directions that could improve our capacity to incorporate bridging into a world
increasingly mediated by algorithms and artificial intelligence.
