Low risk of duplication and redundancy. In contrast to automatic index searching, selective human-compiled lists will not normally throw up multiple hits for the same work. Standard library classification schemes offer the benefits of greater consistency and widespread recognition and acceptance. Listings with annotations or descriptive entries provide more information about the resources listed and increase their potential for usefulness. Entries may be formally structured and use a standard list of fields, much like a library catalogue entry.
Most directories incorporate a search facility which searches just their database of entries.
Subject gateways Taking the work of information professionals in taming the Internet information jungle a step further are the services which bring subject expertise to bear on the selection, classification and description of resources. These services, subject gateways , select, classify and describe quality resources in a specified subject area. They effectively fill the role of information broker for information seekers in that subject. If successful, they can be relied on to identify useful quality online resources, and to be an important resource for anyone working in a field in which there is a significant mass of online source material.