Allow for empty elements

In the next example we will write our grammar to permit empty elements. For example, this input should yield an empty <Date> element:

"Many Lives, Many Masters"/Brian L. Weiss, M.D.//0-671-65786-0/Simon & Schuster Inc.

<Book>

<Title>"Many Lives, Many Masters"</Title>

<Author>Brian L. Weiss, M.D.</Author>

<Date/>

<ISBNɬ-671-65786-0</ISBN>

<Publisher>Simon & Schuster Inc.</Publisher>

</Book>

In the next example we will write our grammar to permit empty elements. For example, this input should yield an empty <Date> element: