File pofi_index.doc.<DATE>  Version 2.1  7/16/92

    CONTENTS OF PRINCIPLES OF INTERPRETATION IN "POFI.DOC"


  Section  Contents
  1        General Principles
  1.1        Only reasonable interpretations will be used
  1.2        Context can rule out interpretations
  1.3        Each interpretation = 1 SQL statement
  1.4        All interpretations will be used
  1.5        Attributes transfer along relational lines
  1.6        Some queries are considered unanswerable
  1.7        Interpretations may incorporate prior context
| 1.8        Constraints from context should be minimized
  2        Specific Principles
  2.1        Requests for Enumeration (tabular)
  2.2        Flights
  2.2.1        Between X and Y = from X to Y
  2.2.2        Definition of "itinerary"
  2.2.3        Stops
  2.2.3.1        Stops = intermediate stops only
  2.3.3.2        Stop info from flight table or flight_stops table
  2.3.3.3        "Stopover" usually means "stop"
  2.2.4        Property transference of multi-leg flights
  2.2.5        References to legs are ambiguous
  2.2.6        Definition of "red-eye flight"
  2.2.7        "Overnight" = "red-eye"
  2.2.8        Location = airport
  2.2.9        "Schedule" = arr. and dep. times for all legs
  2.2.10       Temporal modifiers of flights default to departure time
  2.2.11       "What/where are the stops?" is ambiguous
  2.2.12       "Times for those/that flight(s)"
  2.2.13       "Return on same day" not evaluable

  2.3        Fares
  2.3.1        Definition of "one-way"
  2.3.2        Definition of "round-trip"
  2.3.3        Definition of "cheapest fare"
  2.3.4        Definition of classes of fares
  2.3.5        Definition of rank of fares
  2.3.6        Definition of "discounted fare"
  2.3.7        Definition of "excursion" and "special" fares
  2.3.8        Definition of "cheap" fare
  2.3.9        Fares = fares (+ flights)
  2.3.10       Restrictions are not to be applied implicitly
  2.4        Time
  2.4.1        Time = time of day
  2.4.2        Days = list of day_name fields
  2.4.3        T < 1300 ambiguous between A.M. and P.M.
  2.4.4        Periods of the day (tabular)
  2.4.5        Definition of "earliest"
  2.4.6        Interval endpoints (tabular)
  2.4.7        Definition of "noon"
  2.4.8        Definition of "arriving on X"
  2.4.9        "Wednesday night" begins on Wednesday
  2.4.10       Date of utterance means today, not a year from today
  2.5        Units = units in database
  2.6        Meals
  2.6.1        Snack = a meal
  2.6.2        Types of meal = one tuple per meal
  2.7        "With" clauses (table joins)
  2.8        "Class" = class_of_service.booking_class
  2.9        Meaning Requests
  2.9.1        Defined codes (tabular)
  2.9.2        "Define X", "explain X" = "What does X mean?"
  2.9.3        "More information/everything" = all columns
  2.9.4        "What kind of X is Y?" = "What does Y mean?"
  2.10       Meaning/enumeration ambiguity.
  2.11       Yes/no questions
  2.11.1       Ambiguous between yes/no- and wh-question
  2.11.2       "Is there a difference ..."
  2.11.3       Presupposition failures
  2.11.4       Some yes, some no gives table of "yes"'s only
  2.12       "Near" and "nearby"
  2.13       "American"
  2.14       "The city", "downtown" ambiguous
  2.15       References to aircraft type ambiguous
  2.16       Arithmetic queries not interpretable
  2.17       Tolerances (tabular)
  2.18       Flights, fares, and time/class constraints
  2.19       Prices,costs = fares
  2.20       "Difference"
  2.21       Calendar queries not interpretable
  2.22       Allowable references to Holidays
  2.23       Tuples showing count of 0 optional
  2.24       Airplane size measure is seating capacity.
  2.25       Presupposition of number of answers ignored.
  2.26       "Ticket" may = "fare" or "flight"
  2.27       "Dallas Ft. Worth" and "Baltimore Washington"
  2.28       "What is code Y?" only slightly ambiguous
| 2.29       Requests for "departures" or "arrivals"