The effects of such feedback loops can be powerfully transformative, as shown in the work of historian Philip J. Ethington, a pioneer in incorporating spatial and temporal data into library records (Hunt and Ethington 1997). For more than a decade, Ethington has undertaken an intellectual journey towards what he calls ‘the cartographic imagination’.7 Beginning with the insight that spatial and temporal markers are crucial components of any data record, he conceived a number of digital projects in which meaning is built not according to a linear chain of A following B (a form typical of narrative history) but according to large numbers of connections between two or more networks layered onto one another. He writes in the highly influential website and essay, ‘Los Angeles and the Problem of Urban Historical Knowledge’, that the key element ‘is a space-time phenomenology wherein we take historical knowledge in its material presence as an artifact and map that present through indices of correlation within the dense network of institutions, which themselves are mappable’ (2000: 11).