in a specific order. For example, a program might specify that the ticket
must first contain travel from New York to Tokyo. However, a ticket with
the itinerary of New York–Los Angeles–Honolulu–Tokyo would still
qualify for the commission. Because the commission program did not
specifically exclude this travel, the ticket must qualify for the commis-
sion. The job of sequentially processing the itinerary (the ticket must
still include travel from New York to Tokyo) but allowing for oppor-
tunistic rule firings (recognizing that the additional travel to Los Ange-
les and Honolulu is acceptable) was a sizable task. By using a set of con-
trol facts for both the ticket and commission program information, the
knowledge base was able to procedurally step through such conditions
and still tolerate some deviation. The commission audit knowledge base
also has to cope with occasional missing or inconsistent data from the
electronic transmissions. If the data can be interpreted in more than
one way, all possibilities are explored to determine whether the ticket
satisfies the conditions. As long as one possibility satisfies the condition,
the ticket is still eligible for the commission.
Once the knowledge base completes the audit process, all eligible
commissions for the ticket are output to a C
program. This program
then updates the database and notes any discrepancy between the com-
mission amount determined by the knowledge base and the amount
claimed by the travel agent. All discrepancies are reviewed before any
action is taken.
Implementation
The criteria for choosing an expert system shell specified that the shell
must (1) be rule based, (2) run on a Sun platform, (3) operate in
batch mode, (4) handle text manipulation, (5) be a production release
(no alpha or beta test versions were considered), and (6) be supported
by an established company. The package that best fit these criteria was
ART (automated reasoning tool), an expert system tool by Inference
Corporation. Because ART allows suppression of the graphic user inter-
face, it facilitated the batch implementation of the knowledge bases.
The text-manipulation requirements of fare audit required extensive
string manipulation in Lisp. ART allowed for simple function calls to na-
tive Lisp to format text messages for output.
The auditing functions that the knowledge bases perform are not
limited to tickets sold by Northwest Airlines. Without any modification
of the knowledge bases, the system can audit anyother airline’s passen-
ger tickets. The fare audit knowledge base can audit tickets from any
airline that files its fares with ATPCO. Because commission programs
are specific to a given airline and are not public information, the
8VALLES AND
VAN
LOY