Extract the relationship between entities and answer the following sentences by separating the entities with commas.
This paper introduces a  system for categorizing unknown words . The  system  is based on a  multi-component architecture  where each  component  is responsible for identifying one class of  unknown words . The focus of this paper is the  components  that identify  names  and  spelling errors . Each  component  uses a  decision tree architecture  to combine multiple types of  evidence  about the  unknown word . The  system  is evaluated using data from  live closed captions  - a genre replete with a wide variety of  unknown words .