grammar for search strings?

[Mike Norman]

I have some search strings that I'm passed to Google's AJAX search
API:

http://ajax.googleapis.com/ajax/services/search/web?v=1.0&q="+keyword+"+site%3A"+site

where "keyword" can be:

cost+reduce+OR+reduction+OR+saving

meaning: search for "cost" and ("reduce" OR "reduction" OR "saving")

Example of the most complex search term:

ecosystem+OR+%22value+network%22+OR+%22value+constellation%22+OR+
%22multiple+partners%22+OR+%22external+contributor%22+OR+%22external
+source%22


Is there a grammar for this? Or is all I need is a lexer

Any advice would be greatly appreciated,

Mike Norman