### Question:
WSCXMLKnowledgeBase implements HierarchicalKnowledgeBase, Serializable { public boolean isSubclass(Concept x, Concept y) { return this.subclasses.get(y).contains(x); } WSCXMLKnowledgeBase(InputStream xmlTaxonomyStream);  WSCXMLKnowledgeBase(String xmlTaxonomy);  WSCXMLKnowledgeBase(File xmlTaxonomyFile);  WSCXMLKnowledgeBase(); @Override Concept getConcept(String id); @Override Instance getInstance(String id); @Override Set<Concept> getSubclasses(Concept concept); @Override Set<Concept> getSuperclasses(Concept concept); boolean equivalent(Concept x, Concept y); boolean isSubclass(Concept x, Concept y); boolean isSuperclass(Concept x, Concept y); @Override Concept resolveInstance(Instance instance); Set<Instance> getInstances(Concept concept); Set<Concept> getConcepts(); Set<Instance> getInstances();  }### Answer:
@Test public void testIsSubclass() throws Exception { Concept a = kb.getConcept("con983993996"); Concept b = kb.getConcept("con2025477491"); assertTrue(kb.isSubclass(a,b)); assertFalse(kb.isSubclass(b,a)); }