Expert Systems Questions and Answers

Answer: C

Rete compiles the rule conditions into a network that stores partial matches, so only the consequences of a change are recomputed rather than every rule being retested. It trades memory for speed and made large production systems practical. A star, unification and resolution belong to search and to logical inference. The insight that working memory changes slowly between cycles is what the whole design exploits. Working one numerical case through both cases side by side fixes the distinction better than any rule of thumb.

Answer: D

Temporal redundancy means most facts survive from one cycle to the next, so rebuilding every match from scratch repeats almost all of the previous work. Rete stores the partial matches and updates them incrementally. Relative sizes, sort order and confirmation status are not what the algorithm depends on. Naming the property rather than the network is what lets you predict when Rete will and will not help. The quantity that varies and the quantity that does not are worth naming before any substitution is attempted.

Answer: A

A frame collects the attributes of a concept as slots, each able to carry a value, a default, a type restriction or an attached procedure. Frames support inheritance along an is-a hierarchy, which rules do not. Decision tables and certainty factors serve different purposes entirely. Frames and rules are usually combined rather than opposed, with frames holding the objects and rules holding the reasoning about them. A single measurement chosen to respond to the one asymmetry beats several that respond to shared behaviour.

Answer: B

A default fills the slot with a typical value that later evidence may override, which is how frames express stereotypes economically. Demons are attached procedures, facets are the sub-fields describing a slot, and inheritance is the mechanism by which a default is often obtained. The ability to override a default is what makes frame reasoning non-monotonic in the same way that human expectations are. A single measurement chosen to respond to the one asymmetry beats several that respond to shared behaviour.

Answer: C

A demon is procedural knowledge attached to a slot, triggered when the slot is read, written or needed, and it is how frames compute values instead of merely storing them. If-needed and if-added demons are the standard varieties. Defaults, facets and restrictions are declarative features. Attaching procedures to data was the frame system's answer to the question of where computation belongs in a declarative representation. Working one numerical case through both cases side by side fixes the distinction better than any rule of thumb.

Answer: D

A semantic network draws concepts as nodes and relations as labelled directed arcs, with is-a arcs carrying inheritance. It is the ancestor of both frames and description logics. Production systems, blackboards and truth maintenance address control, cooperation and belief revision respectively. The network's weakness, that arc labels have no fixed semantics, is exactly what description logics were later designed to repair. The quantity that varies and the quantity that does not are worth naming before any substitution is attempted.

Answer: A

A blackboard holds an evolving solution that independent knowledge sources inspect and extend whenever they can contribute, coordinated by a control component. It suits problems with no fixed solution path, such as speech understanding, where HEARSAY-II introduced it. Chaining, shells and hierarchies are different concerns. The metaphor of specialists round a shared board is the clearest statement of the idea. Most errors here come from carrying a result across from a neighbouring case where it does not hold.

Answer: B

MYCIN advised on bacterial infections of the blood and on antibiotic therapy, using about six hundred backward-chaining rules and certainty factors. It was never deployed clinically but established the architecture, the explanation facility and the shell idea. DENDRAL handled chemistry, XCON configured computers and PROSPECTOR assessed ore bodies. Knowing which system did what is standard examination material in this topic. Reading the definition literally, rather than recalling a formula, is the reliable route through questions of this shape.

Answer: C

EMYCIN is MYCIN with the medical knowledge removed, leaving the inference engine, the explanation facility and the acquisition tools for use in any domain. It demonstrated that the architecture, not the knowledge, was the reusable part. TEIRESIAS, NEOMYCIN and GUIDON were other MYCIN descendants, aimed at acquisition, teaching strategy and tutoring. The shell concept is the single most influential product of the whole project. The shared properties explain why these belong to one family, and the differences explain why more than one exists.

Answer: D

XCON, also called R1, configured VAX orders for Digital Equipment Corporation and is the standard example of a commercially successful expert system. It chained forward, matching the task's data-driven character, and grew to thousands of rules. MYCIN, DENDRAL and INTERNIST addressed medicine and chemistry. XCON is also the standard example of the maintenance burden a large rule base eventually imposes. The shared properties explain why these belong to one family, and the differences explain why more than one exists.