XPointer specifies complex Links like bi-directional links and allows the location of a specific part of XML document. Any fragment identifier that points into an XML resource must be an Xpointer. Both these languages need to navigate an XML document and hence the navigation part was extracted out as a separate language Xpath. XPath gets its name from the use of a path notation as in URLs for navigating through the hierarchical structure of an XML document. It uses a compact, non-XML syntax to facilitate it s use within URIs and XML attribute values and operates on the abstract, logical structure of an XML document, rather than its surface syntax.
Expression evaluation occurs with respect to a context.
XSLT and XPointer specify how the context is determined for XPath expressions used in XSLT and XPointer respectively. We decided to use a tool that required minimum efforts to set up the testing tool. XT is a Java utility that needs two input files - a .xml file containing XML document and .xsl file containing XSLT intructions with embedded Xpath instructions. No compiling or elaborate coding is necessary to test the various navigational combinations. And here is an example of .xsl file with embedded Xpath instructions.