Storage of Placement Data
   3 types of fields
      multi-valued fields:  temporary placement for CS, statistics, math  
      numeric data:  ACT, SAT, semesters taken
      enumerated types:  standardized scores, grades
   'unknown' always a possible value

Processing Data Values
   numeric data:  simple comparison (=, !=, <=, <, >=, >)
   enumerated types:  translate to underlying code, then compare
   multi-valued fields:  check if specific value present

Rules
   analysis of standard scores follows simple table
   remaining analysis based on qualification rules
   
Rule Structure
   hierarchical (directed graph, no cycles)
   standard scores depend upon SAT, ACT, SAT II
   tentative math placement depends upon standard scores, math taken
   math placement selects highest tentative math placement
   tentative CS or stat placement depends upon 
       standard scores, cs, stat, math placements
   cs, stat placements select highest tentative cs, stat placements
   
Inference Engine
   Basic algorithm:
      goals in array
      for each goal in array
          for each rule in rule base
              if rule might meet goal
                  if rule already tried, skip rule
                  else for each condition
                      if condition known, 
                          check if true
                      else
                          find rule to meet goal and check recursively
                  when all conditions checked or some fail
                      mark rule has been tried
                          (e.g., prop[rule] = "checked")
                  if result holds
                      record result in prop array
                      break from goal search
                         
   Example:  Apply approach to sample student for CS placement