CS 47/147 Advanced Object-Oriented Programming - Caltech

Book Example: File SystemFileDir?• “parent” is a relation betweendirectories.– Formally, parent ⊆ Dir×Dir.– Draw as arrow from Dir to Dir.– “children” is its inverse:(e,d) ∈ children iff(d,e) ∈ parent.*parent (~children)• An important constraint:– For d ∈ Dir,∃ ≤ 1 e with (d,e) ∈ parent.– Indicate multiplicities on endsof arrow:? = at most 1; ! = exactly 1;+ = at least 1; * = any number15