Knowledge is hard to acquire from specialists. The difficulties stem from a number of factors. First, specialists are not good at recalling and explaining everything they know. They have what is termed tacit knowledge which operates at a subconscious level and is thus hard, if not impossible, to explain. Second, specialists have different experiences and opinions. Third, specialists develop particular conceptualizations and mental shortcuts that are not easy to communicate. Fourth, specialists use jargon and assume most other people understand the terminology they use. In addition to these difficulties are other problems associated with representing and storing knowledge, such as the grain size of the knowledge and the representation formalism.