there are three basic types of queries supported by this interface

simple tokens:

openid

this is the most common type of query. it searches for the indicated string in the text and selected attributes (e.g. title and alt) in a case insensitive manner.

tokens match on word boundaries, and can not contain spaces. if multiple tokens are specified, each must be present in the entry in any order.

regular expressions:

/mash[-\s]?up/

regular expressions must begin and end with a forward slash, and the search is done in the same areas of the entry as simple tokens. seach is done in a case insensitive manner, but if you want to enforce word boundaries, you must put \b at the beginning and end of your expression

multiple regular expressions are possible, separated by whitespace. in fact, regular expressions and simple tokens may be mixed. if you want to match whitespace characters in your regular expression use \s.

xpath expressions:

//xhtml:img[contains(@src,'flickr.com')]

xpath expressions have acess to the full, normalized, atom 1.0 entry, and can access any element or attribute. if the xpath expression matches any node in an entry, then the entire entry is returned.

xpath expressions may make use of the following namespace prefixes:

prefix	namespace
atom	http://www.w3.org/2005/atom
mathml	http://www.w3.org/1998/math/mathml
planet	http://planet.intertwingly.net/
svg	http://www.w3.org/2000/svg
xhtml	http://www.w3.org/1999/xhtml
xlink	http://www.w3.org/1999/xlink/