@staticmethod
def findValueInRDF(prop, prefixPath, ns, tag):
    """Find a value in RDF : first as an element then as an attribute."""
    path = prefixPath + '/' + ns + tag
    value = prop.find(path)
    if value is not None:
        return value.text
    value = prop.find(prefixPath).attrib.get(ns + tag, None)
    if value and value is not None:
        return value
    return None
