is
If the guid element has an attribute named isPermaLink with a value of true, the reader may assume that it is a permalink to the item, that is, a url that can be opened in a Web browser, that points to the full item described by the <item> element.
An example:
<guid isPermaLink="true">http://inessential.com/2002/09/01.php#a2</guid>Content copied to clipboard
isPermaLink is optional, its default value is true. If its value is false, the guid may not be assumed to be a url, or a url to anything in particular.