Graphs, as a model of computation and as a means of interaction and authorship, have found success in specific domains such as shader programming and signal processing. In these systems, computation is often expressed on nodes of specific types, with edges representing the flow of information. This is a powerful and general-purpose model, but it incentivises a closed-world environment where both node and edge types are decided at design-time. By choosing an alternate topology where computation is represented by edges, the incentive for a closed environment disappears. Scoped Propagators are a programming model designed to be embedded within existing environments and user interfaces.