Listing 2: Subscription filter used by the context processing entity
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	and value=‘48,52 .* N, 2,18 .* E’
6	XMLdocument, XPathConstants.NODESET).length == 0) &&
7	(XPath.evaluate(“⫽observation[uri=‘/pollution/carbon-monoxide’ and unit=‘ppm’]”,
8	XMLdocument, XPathConstants.NODESET).length == 0)) {
9	return false;
10	}
11	if((XPath.evaluate(“⫽QoCIndicator[@id=‘10’ and
12	QoCCriterion[@id=‘[10.1]’]/QoCMetricDefinition[@id=‘10.1’]]”,
13	XMLdocument, XPathConstants.NODESET).length == 0) &&
14	(XPath.evaluate(“⫽QoCIndicator[@id=‘7’ and
15	QoCCriterion[@id=‘[7.1]’]/QoCMetricDefinition[@id=‘7.1’]]”,
16	XMLdocument, XPathConstants.NODESET).length == 0) &&
17	( (XPath.evaluate(“⫽QoCIndicator[@id=‘15’ and
18	QoCCriterion[@id=‘[15.1]’]/QoCMetricDefinition[@id=‘15.1’]]”,
19	XMLdocument, XPathConstants.NODESET).length == 0) ‖
20	(XPath.evaluate(“⫽QoCIndicator[@id=‘18’ and
21	QoCCriterion[@id=‘[18.1]’]/QoCMetricDefinition[@id=‘18.1’]]”,
22	XMLdocument, XPathConstants.NODESET).length == 0) ) {
23	return false;
24	}
25	return true;
26	}