The spatial operators DWithin and Beyond test whether the value of a geometric property is within or beyond a specified distance of the specified literal geometric value. Distance values are expressed using the <Distance> element. The content of the <Distance> element represents the magnitude of the distance and the units attribute is used to specify the units of measure. The units attribute is of type anyURI so that it may be used to reference a units dictionary. For example, the following XML fragment:
<Distance unit="http://www.uomdict.com/uom.html#meters">10</Distance>
encodes a distance value of 10 meters. The units of measure dictionary should be encoded in GML.