How to build a XQuery for extracting values from XML

Hi,

I think the best FME Transfomer for such type of extractions is the "XMLXQueryExtractor", but I do not know how to build the query.

The XML is contained within an attribute and could be something like this:

"<?xml version="1.0" encoding="UTF-16"?><value xmlns="http://spec.tn-its.eu/schemas/"> <gml:measure uom="kph" xmlns:gml="http://www.opengis.net/gml/3.2">50</gml:measure> </value>"

For that particular case, I wanted to extract that "50" value from that XML.

Thanks!