Commas are not part of the query language. I think I may have been wrong about double-quoting being exact phrase searches... playing with it a little bit it looks like a search for "dc motor" (with quotes) is the same as dc motor (without quotes) and dc AND motor (without quotes).
[Checking code now...] It's been a while since I wrote that stuff after checking the code I see that actually strip out lots of punctuation that could be used to try to change the logic of the query (so, it will ignore double-quotes, single-quotes, parenthesis, and commas) and also the words AND and OR. It turns out that a two-word query will be "expanded" into an OR search that ranks documents that have all of the words better than those with only some of them.
Well, I just took a look at the code and at queries that people have run and I'm definitely not going to define a complex search grammar. What I can easily do is detect the case of a multi-term query that is entirely quoted and then run that as a true phrase search. (Not released yet, but done.) If I had more time I'm sure something better could be done but it won't be any time soon.
I just swapped to a new tab (in IE7) and did an 'advance search' with google for dc motor within CR4. It seemed to churn out plenty. It's not exactly the point being addressed, but may be of use. My knowledge of search methods is very basic, but the method looked viable. The advance search in google can certainly be used to restrict search to within CR4, and hence Google's search parameters can be used. I guess people not using tabbed browsing could open a second browser window. Another long shot is the possibility for interested users to build their own custom Google Gadget - again, it's something I know little of ( my knowledge gaps seem to be expanding !), so I'm not sure if that can be done.
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