Attributes are in key-value form, and if there's no value provided for an attribute, a NotAvailableValueError will be raised.

Methods
N
Attributes
[R] attribute
[R] tag
[R] value
Class Public methods
new(tag, value, attribute=nil)

Source: show 

# File lib/rss/rss.rb, line 153
def initialize(tag, value, attribute=nil)
  @tag, @value, @attribute = tag, value, attribute
  message = "value <#{value}> of "
  message << "attribute <#{attribute}> of " if attribute
  message << "tag <#{tag}> is not available."
  super(message)
end