Standards, resources, including free implementations for the SRU effort.
SRU: the protocol – SearchRetrieve Operation: Binding for SRU 2.0 (draft)
CQL: The Contextual Query Language – CQL: The Contextual Query Language (draft)
The website reports that standardization is to be completed soon. And the available drafts date from 2010.
However, if you follow known servers you will find only thirteen (13) known servers as of 12 December 2010.
Standards can be written prior to wide spread adoption but before spending too much effort on this protocol and query language, I think we need to watch its adoption curve closely.