2007/2/13, Calum Benson <[EMAIL PROTECTED]>:
On Mon, 2007-01-29 at 12:51 +0100, Mikkel Kamstrup Erlandsen wrote: > 2007/1/29, Jean-Francois Dockes <[EMAIL PROTECTED]>: > Mikkel Kamstrup Erlandsen writes: > > Hi All, > > > > I put together a first take on formalizing an end user > search language. > > > > http://wiki.freedesktop.org/wiki/WasabiUserSearchLanguage > > - Which of OR and AND has priority ? (does (A AND B OR C) mean > ((A AND B) OR C) or (A AND (B OR C)) ? > > I guess it is standard that AND takes precedence over OR, but maybe it > makes sense to reverse that in our case. This is a perennial problem with designing boolean query UIs for average (i.e. non-mathematically-trained) users-- they expect "and", "or" and "not" to mean the same as they do in everyday language, but often they don't. E.g.: - User asks for a list of "blue things and red things", and gets back a list of things that are both blue AND red (which in many contexts is an empty list). - User asks for a list of things that are "not blue or green", and gets back a list of things that are every colour except blue (including green). FWIW, this is why I personally prefer something like the eBay search "language" to Google's-- I always find it easier to remember how to construct more complex queries, and they never involve typing "and" or "or" :) (But of course, I'm not really your "average user" either.)
I was not familiar with the eBay search language. I must say that I'm not really thrilled at they way they use braces - ie. they are not subexpressions. Also - you have to read the language spec to know what they do. Also, I must say that I've got cold feet with regards to let OR have precedence over AND. Is it not safe to assume that people that use logical operators (which I'm willing to bet is a minority) knows that AND usually takes precedence over OR? An alternative could be to let whitespace be a SAND="Strong AND" that takes precedence over normal AND. That way your "blue things and red things" would find the expected. This may have unwanted consequences though, I haven't really thought it through. Cheers, Mikkel
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