public boolean contains(
String term,
String scheme)
throws IRISyntaxException {
List<Category> categories = getCategories();
IRI catscheme = getScheme();
IRI uri = (scheme != null) ?
new IRI(scheme) : catscheme;
for (Category category : categories) {
String t = category.getTerm();
IRI s = (category.getScheme() != null) ?
category.getScheme() : catscheme;
if (t.equals(term) &&
((uri!=null)? uri.equals(s) : s == null))
return true;
}