Version Space

Add structured variables  (did 1988)
Add internal disjunction or negation
Add linear variables (closing interval)  (did 1989)
Add language for n independent  object descriptions (structure)  (did 1990)
Add language for kDNF, kCNF, or other somesuch language

ID3

make n category (did 1988)
eliminate null leaves (did 1990)
change selection criteria (gain ratio, did 1989)
add numerical features
make iterative
enlarge search (i.e. keep track of more than the best, beam search)
handle noise  (chi-square, post pruning, no-chi)
handle missing (most-common, change gain)

AQ

Add tolereances to the LEF
Add ability to do disjoint covers
Add internal disjunction, negation, structured vars, linear vars etc.
Add some good LEF criteria
Change matching of rule to instance to be more probabilistic
