Descriptive adjectives answer the question, What quality does it have?, whereas classificatory (also known as relational) adjectives answer the question, What kind is it?
Ex: My cat is a Siamese cat. [+Classificatory]
Check out this page: ADJECTIVE PHRASE, and additional examples here (Scroll down to 9.) There's also this paper, Relational adjectives and the property of kinds by Louise McNally (2004), which is cited in this paper (Scroll down to section 2.1 on page 3).