Listing 4: Subscription filter used by the healthcare application
1	function evaluate(XMLdocument) {
2	importPackage(javax.xml.xpath);
3	var XPath = XPathFactory.newInstance().newXPath();
4	if((XPath.evaluate(“⫽observable[uri=‘/location’ and unit=‘title’]”,
5	XMLdocument, XPathConstants.NODESET).length == 0) &&
6	(XPath.evaluate(“⫽observation[uri=‘/pollution-level’ and unit=‘AQI’]”,
7	XMLdocument, XPathConstants.NODESET).length == 0)) {
8	return false;
9	}
10	if((XPath.evaluate(“⫽QoCIndicator[@id=‘17’ and
11	QoCCriterion[@id=‘[17.1]’]/QoCMetricDefinition[@id=‘17.1’] and QoCMetricValue[@name=‘High’]]”,
12	XMLdocument, XPathConstants.NODESET).length == 0) ) {
13	return false;
14	}
15	return true;
16	}