Finding a plumber. Typically you start with your own experience, or a referral from a friend, or maybe by an online search. Type in "Plumber" and your zip code and a list appears - quantity and with refinement, the possibility of some type of quality assessment. What if you work for a large organization and you are interested in locating an in-house corrosion control engineer. You probably would follow the same trail as your search for a plumber.
The internal database might be problem. To date, most such systems are centrally managed efforts and that's a problem. The typical setup identifies and catalogs experts in a searchable directory or database that includes descriptions of the experts knowledge and experience, and sometimes links to samples of their work, such as research reports.
Two primary problems are embedded in this approach. The first is the system is not dynamic and does not capture the constant changing credentials and role of the experts. Second, users of these systems need more than a list of who knows what among employees. They also need to gauge the experts' "softer" qualities such as - trustworthiness, communication skills, willingness to help, experience, currency of knowledge, awareness of other resources, and extent of knowledge. It isn't easy for a centrally managed database to offer opinions in these areas without crossing delicate political and cultural boundaries. You basically end up with a system where workers in search of expertise within their own organization often don't know where to turn.
New systems, so called expertise-locator systems, are search systems that apply social-computing tools such as internal blogs, wikis, and social networks. A search engine that mines internal blogs, for example, where workers post updates and field queries about their work, will help searchers judge for themselves who is an expert in a given field. Blog mining can provide the extent of knowledge (from posts), trustworthiness (through communications), communication skills (written), and willingness to help (signaled through interactions via feedback via commenting mechanisms). Social network sites demonstrate trustworthiness (through shared ties) and awareness of other resources (through network structure). Wiki sites, because they involve collaborative work, suggest extent of knowledge (through contributions), trustworthiness (through collaboration), communication skills (written), and a willingness to help (signaled through collaboration). Tags and key words, which are posted by employees and serve as flags for search engines, can reveal work experience, currency of knowledge, and extent of knowledge (mostly self-reported).