We propose an approach to content-based Distributed Information Retrieval based on the periodic and incremental centralisation of full-content indices of widely dispersed and autonomously managed document sources. Inspired by the success of the Open Archive Initiative's protocol for metadata harvesting, the approach occupies middle ground between content crawling and distributed retrieval. As in crawling, some data moves towards the retrieval process, but it is statistics about the content rather than content itself; this grants more 1