Increasingly, digital libraries are being defined that collect pointers to World-Wide Web based resources rather than hold the resources themselves. Maintaining these collections is challenging due to distributed document ownership and high fluidity. Typically a collection's maintainer has to assess the relevance of changes with little system aid. In this paper, we describe the Walden's Paths Path Manager, which assists a maintainer in discovering when relevant changes occur to linked resources. The approach and system design was informed by a study of how humans perceive changes of Web pages. The study indicated that structural changes are key in determining the overall change and that presentation changes are considered irrelevant.