Expected value for the author property

Maybe this is an oversight on my part that I didn't notice it before 
this week or maybe this is a recent change, but I noticed that on the 
schema.org/Review page as well as on other pages, the expected value for 
the author property is Person or Organization.  For a long time, the 
author's name was simply declared with text, and the examples that exist 
on schema.org as well as in Google's rich snippet guidelines all show 
the value of the author property as text.  So is this a new standard, 
and when using the author property, is the expected value now a Person 
or Organization?  And will declaring the author simply with text no 
longer suffice?

Also interesting is the author property's definition: /The author of 
this content. Please note that author is special in that HTML 5 provides 
a special mechanism for indicating authorship via the rel tag. That is 
equivalent to this and may be used interchangeably./  If I understand 
this correctly, it would seem that this is stating that the author could 
be declared by using the rel=author tag.  But could someone please 
explain this definition a little more as well as how the author property 
could/should be declared moving forward, either with or without the rel 
tag?  Maybe some examples would be nice.  :-)

Thanks in advance.

David