1. A method of assisting a user in browsing in an electronic catalog of media items, the method comprising: (a) obtaining access to co-concurrency metric values derived from a knowledge base of mediasets associated with the electronic catalog; wherein the metric values reflect a level of co-concurrency for each of the pairs of media items within the knowledge base of mediasets and the co-concurrency metric values are independent of the content of the media items; and further wherein the co-concurrency metric values indicate, for each pair of media items (i,j), how many times item i and item j appear together within any of the mediasets of the knowledge base, so that the co-concurrency metric values are not affected by any descriptor, characteristic, rating, classification or attribute of the media items' content; (b) receiving from the user an initial selection of at least one media item from the catalog to define an initial input media set; (c) for each item of the initial input media set, generating at least one navigation list based on the co-concurrency metric values; (d) communicating the generated navigation list to the user; (e) receiving from the user an instruction to edit the navigation list; (f) editing the navigation list as instructed by the user to define a new input set; (g) for each item of the new input media set, generating a new navigation list based on the co-concurrency metric values; and (h) communicating the new navigation list to the user.