[ontolog-forum] Intensional relation

[Juan de Nadie <juandenavas@xxxxxxxxx>]

Hi.
I'm reading the Guarino's paper "What is an ontology". The paper is very interesting. 

But I had some troubles in understand some mathematics. I apologize in advance for my question, since I think that it is very basic one. My doubts are regarding the definition 2.3 of the paper (Intensional relation, or conceptual relation), in page 6. In this definition, Guarino says that:  

"An intensional relation (or conceptual relation) ρⁿ of arity n on <D,W> is a total function ρⁿ : W → ₂Dⁿ from the set W into the set of all n-ary (extensional) relations on D"

I don't understand the ₂Dⁿ, mainly this base 2. Why 2? I think that I don't understand very well the mathematical structures underlying this notions.

Can someone help me in this subject?

Thank you in advance.

Best regards.

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