Just in order to wrap my head around what you propose: 
Properties:
id|A/V-pairs
-----------------
 0|colour:red
 1|colour:green
 2|material:metal
 3|colour:blue
 4|material:wood
 5|surface:rough
And then our thing db: 
things:
bitmap|thing
012345|name
-----------------
101011|red-metal-wood-rough-Thing
001101|metal-blue-rough-Thing
01    |green-Thing

Right?? So far so good, now fetching records: 
sub getBits {
  # lookup: colour:red -> is id/bitposition:0
  # lookup: material:wood -> is id/bitposition:4
}

my $bits = getBits('red-wood'); # $bits is 10001
my $nBits = unpack '%32b*', $bits; # http://docstore.mik.ua/orelly/per
+l/prog/ch03_182.htm : "efficiently counts the number of set bits in a
+ bit vector"

for my $straw ( @haystack ){ # loop over all records and compare
    my $similarity = unpack '%32b*', $straw & needle; # compute a delt
+a
    print "Percentage similarity %f\n", $similarity / $nBits * 100; # 
+delta in relation to nbits benchmark ("distance")
}

# then, sort by similarity

[download]
Questions:
- Did I get that right?
- Let's assume we've got millions of records, is that looping+comparing efficient?
- Any suggestions for a storage backend to implement that? Might be, there's one that offers bitmap-comparisons

In reply to Re^4: What is the best way to store and look-up a "similarity vector"? by isync
in thread What is the best way to store and look-up a "similarity vector" (correlating, similar, high-dimensional vectors)? by isync

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