Pipelined XPath Query Based on Cost Optimization

Table 2

Syntax of XPath subset.

Expression name	Syntax
Path expression	Path::= Step(‘/’ Step)
Query step	Step:: = Axis Tag | Axis Tag ‘[’ Pred ‘]’
Axis	Axis::= PA | CH | AN | DS | AT | PS | FS | PP | FF
Tag for node test	Tag::= String |
Predicate	Pred::= Path | Pred ‘or’ Pred | Pred ‘and’ Pred | ‘not’ ‘(’ Pred ‘)’ | Num