The RVs have been shown on the BKB as a dotted oval, however in the actual BKB there is no explicit representation of components. In a BKB, a support node with no parents is called a root support. Banks, Darwin O. Acquiring consistent Knowledge for Bayesian Forests . MS thesis, Air Force Institute of Technology, March 1995. This allows it to accommodate incomplete as well as uncertain knowledge.
Any knowledge representation is of little use without a means of knowledge acquisition.
MACK supports an incremental knowledge acquisition philosophy, allowing the knowledge engineer freedom in constructing the knowledge base. In simpler terms, inferencing results in an assessment of the most probable state of the partial world defined by the evidence and the look beyond factor. This occurs due to a conflict between strict adherence to probabilistic semantics and a lack of information. To overcome this problem, a type of default reasoning is invoked. Banks, Darwyn O. Acquiring Consistent Knowledge for Bayesian Forests .