And because the resources are human-selected, there is likely to be a better chance of locating quality information than with a search engine. The disadvantage of this approach is that you cannot always predict how a subject will be classified. Thus your descent through the hierarchy may lead to a dead-end. When searching a classified directory, however, it is important to remember you are searching the catalogue record created for that resource, not the full text of the resource itself. Some classified directories also include abstracts or reviews, which can be very useful in sifting through long lists of resources.
Subject gateways are simply classified directories that are devoted to one specific subject.
Selected resources Selectivity may well compensate for lack of comprehensiveness in some cases, for instance, in searching for a standard or classic work in a subject area. Improved chance of finding quality resources Even though many items may be self-selected by their authors, many will also have been selected for inclusion because they have been found useful by others. In contrast to automatic index searching, selective human-compiled lists will not normally throw up multiple hits for the same work. Subject organization One disadvantage of using a classified directory is that you cannot always predict how a subject will be classified. Standard library classification schemes offer the benefits of greater consistency and widespread recognition and acceptance.