Sometimes the answer is not missing; the route to the person who knows it is missing. An expert directory provides that route. It records areas of experience and a way to approach the people who hold them.
An expertise-location system differs from a library of answers. It helps someone find a person who can interpret an unfamiliar situation, ask clarifying questions, or explain knowledge that has not been written down.
Find the right kind of experience
Suppose a network of community gardens wants advice about negotiating access to land. A directory that lists “gardening” beside every member is not enough. Someone’s experience obtaining a temporary lease may be more relevant than another person’s extensive horticultural expertise. Concrete descriptions of projects and situations make the directory useful.
Finding a name does not entitle the searcher to that person’s time. Contact preferences, availability, and limits on what someone can help with prevent the directory from becoming an unmanaged stream of requests to a few generous members. Where a direct approach would be awkward, an introduction by a mutual contact can provide a more personal route in.
Entries also need renewal. A title may outlive someone’s interest or competence, while quiet newcomers may possess valuable experience that remains unlisted. The directory works best as an invitation to make relevant knowledge discoverable, not as a permanent ranking of who deserves to be called an expert.