Parallel Inheritance

There are two(+) associated classes A, B, and every sub type of A is associated with a (different?) sub type of B. e.g ProductEditor provides UI for a Product. Curtains and Books are different type of Products. CurtainEditor provides UI for Curtain. BookEditor provides UI for Book. And so on. Is this a CodeSmell?

If there is duplicate parallel relationship child classes, managing the duplicate relationship can be a problem.

class Product
{
}

class Book extends Product
{
}

class ProductEditor
{
  private Product product;
  public void setProduct(Product prd)
  {
    this.product = prd;
  }
}

class BookEditor extends ProductEditor
{
  // need to be careful?
  private Book book;

  public void setProduct(Book book)
  {
    this.product = prd; // need to call super also
  }
}


BookEditor bookEditor = ...;
Product product = new Book(...);
bookEditor.setProduct(product); // calls base class method.
Book book = new Book(...);
bookEditor.setProduct(product); // calls chile class methods.


Adding duplicate relationship for convenience is bad. Apart for code duplication, if not done correctly, there could be dangling/spurious references.
How ever I don't think this is a code smell (due to its -ve meaning).In fact relation ships among parallel inheritance hiearchies is common in many frameworks (is a good smell?). Are not these relations cornerstone for template methods?When such relation ships exist,

• Document them and advise against duplicate relations.
• If needed provide a controlled relation ship managers for setting relations among the participant Objects (do we need a DIP for this?)