17. The system of claim 13 , wherein the query language accepts both local backreferences and remote backreferences, wherein each local backreference is limited to retrieving a captured substring of a string matching a regular expression that is within the same condition as the local backreference.
17. The system of claim 13 , wherein the query language accepts both local backreferences and remote backreferences, wherein each local backreference is limited to retrieving a captured substring of a string matching a regular expression that is within the same condition as the local backreference. 18. The system of claim 17 , wherein when the query language provides for local and remote backreferences in the query to be numbered with a same sequential numbering system.