TypeInstanceHomonym

For those who care for stuff like this:

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...
In the first sentence 'book' refers to a literary work, one that's been with us for over a hundred years. In the second sentence 'book' now refers to a physical object that's probably been around for a lot less. I can easily destroy the latter in my fire, but the former isn't touched by my flames and will doubtless last longer than I will. I can put the former on my hard disk with many siblings that collectively weigh less than the latter.
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First-class relationships in an object-oriented language

By Gavin Bierman and Alisdair Wren

"In this paper we investigate the addition of first-class relationships to a prototypical object-oriented programming language (a “middleweight” fragment of Java). We provide language-level constructs to declare relationships between classes and to manipulate relationship instances. We allow relationships to have attributes and provide a novel notion of relationship inheritance. ..."
http://homepages.inf.ed.ac.uk/wadler/fool/program/final/4/4_Paper.pdf