QUB political sociologist Katy Hayward has developed four key analysis areas of what border controls mean for different types of border with the EU.
1. Scale of customs controls on the movement of goods across an EU border, depending on the trade relationship a country has with the EU.
2. What customs controls mean in practice for operators and customs agencies.
3. What technology can do at a border and what is still nonetheless required to enforce a customs border.
4. The possible scenarios for UK/EU, GB/NI and NI/IRL border in light of the UK/EU Joint Report of 8 December.