very nicely done! And fun.
- thomas
Shinji,
Great piece of work! Did I miss that bit in the AQL specs, or are you supporting some functions of your own, such as devide?
Hi Seref and Thomas,
This is a piece of work of Prof Subash Bhalla Laboratory in Aizu
university in Japan.
http://www.u-aizu.ac.jp/e-intro/e-faculty/e-undergraduate/e-undergraduate3/e-bhalla.html
They use Scala with Java library.(not Ruby 
I can refer you to them anytime.
Cheers,
Shinji
One quick piece of feedback - any free-text field probably should not
just have = / != operators but a matching operator like %, or 'contains'
or 'matches' with a regular expression as the argument.
- thomas