Listing 1: Advertisement filter used by the bus stations
1	function evaluate(XMLdocument) {
2	importPackage(javax.xml.xpath);
3	var XPath = XPathFactory.newInstance().newXPath();
4	if((XPath.evaluate(“⫽observable[uri=‘/location’ and unit=‘WGS84’]”,
5	XMLdocument, XPathConstants.NODESET).length == 0) &&
6	(XPath.evaluate(“⫽observation[uri=‘/pollution/carbon-monoxide’ and unit=‘ppm’]”,
7	XMLdocument, XPathConstants.NODESET).length == 0)) {
8	return false;
9	}
10	if((XPath.evaluate(“⫽QoCIndicator[@id=‘10’ and
11	QoCCriterion[@id=‘[10.1]’]/QoCMetricDefinition[@id=‘10.1’]]”,
12	XMLdocument, XPathConstants.NODESET).length == 0) &&
13	(XPath.evaluate(“⫽QoCIndicator[@id=‘7’ and
14	QoCCriterion[@id=‘[7.1]’]/QoCMetricDefinition[@id=‘7.1’] and QoCMetricValue[@value<=‘50’]]”,
15	XMLdocument, XPathConstants.NODESET).length == 0) &&
16	(XPath.evaluate(“⫽QoCIndicator[@id=‘15’ and
17	QoCCriterion[@id=‘[15.1]’]/QoCMetricDefinition[@id=‘15.1’] and QoCMetricValue[@value<=‘30’]]”,
18	XMLdocument, XPathConstants.NODESET).length == 0)) {
19	return false;
20	}
21	return true;
22	}