As in SAX, features are boolean; properties have object values.
Features and properties are named by URIs.
All features are false by default.
Properties aren't used much.
    public void setFeature(String name, boolean state) 
     throws XmlPullParserException;
    public boolean getFeature(String name);
    public void setProperty(String name, Object value)
     throws XmlPullParserException;
    public Object getProperty(String name);