http://xmlgraphics.apache.org/fop/: Apache FOP (Formatting Objects Processor) is the world's first print formatter driven by XSL formatting objects (XSL-FO) and the world's first output independent formatter. It is a Java application that reads a formatting object (FO) tree and renders the resulting pages to a specified output. Output formats currently supported include PDF, PCL, PS, AFP, TIFF, PNG, SVG, XML (area tree representation), Print, AWT and TXT. The primary output target is PDF. (Apache Software Foundation) 
public interface org.apache.fop.layoutmgr.ElementListObserver$Observer
  minor version: 0
  major version: 59
  flags: flags: (0x0601) ACC_PUBLIC, ACC_INTERFACE, ACC_ABSTRACT
  this_class: org.apache.fop.layoutmgr.ElementListObserver$Observer
  super_class: java.lang.Object
{
  public abstract void observe(java.util.List, java.lang.String, java.lang.String);
    descriptor: (Ljava/util/List;Ljava/lang/String;Ljava/lang/String;)V
    flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT
    MethodParameters:
             Name  Flags
      elementList  
      category     
      id           
}
SourceFile: "ElementListObserver.java"
NestHost: org.apache.fop.layoutmgr.ElementListObserver
InnerClasses:
  public abstract Observer = org.apache.fop.layoutmgr.ElementListObserver$Observer of org.apache.fop.layoutmgr.ElementListObserver