Abstract system -- exemplary interface

library 



  p = new person();
  b = new book();
  p = b->borrower;
  s = p->books;
  tf = b->inlibrary();
  b->borrow(p);
  p->allocate(b);
  p->deallocate(b);
  b->_return(p);

For person* p; book* b; set<book>* s; bool tf;

slide: The library system