XML Signature Streaming Profile of XPath 1.0
http://www.w3.org/2008/xmlsec/Drafts/xmldsig-xpath/ In general I don't think it is good idea to create yet another XPath subset. Proliferation of XPath subsetting prevents using standalone XPath libraries when implementing various subsets of the language. If streaming is necessary then effort should be derived from XSLT 3.0 which provides streaming facilities.