In the setting of The Integers and the Rational Numbers, with the Natural Numbers and the Integers Identified with Subsets of the Rationals , let < < < be the strict relation of the order ≤ \le ≤ of Q \mathbb{Q} Q , and let C C C be the class of those subsets x x x of Q \mathbb{Q} Q , that is, elements of the power set P ( Q ) \mathcal{P}(\mathbb{Q}) P ( Q ) , such that x ≠ ∅ x\neq\emptyset x = ∅ , x ≠ Q x\neq\mathbb{Q} x = Q , every v ∈ Q v\in\mathbb{Q} v ∈ Q with v < u v<u v < u for some u ∈ x u\in x u ∈ x lies in x x x , and every u ∈ x u\in x u ∈ x has some v ∈ x v\in x v ∈ x with u < v u<v u < v . Let ≤ C \le_{C} ≤ C be the class of pairs ( x , y ) (x,y) ( x , y ) in the Cartesian product C × C C\times C C × C with x ⊆ y x\subseteq y x ⊆ y . For u ∈ Q u\in\mathbb{Q} u ∈ Q and x , y ∈ C x,y\in C x , y ∈ C let
u ∗ = { v ∈ Q : v < u } , x ⊕ y = { w ∈ Q : ∃ u ∃ v ( u ∈ Q ∧ v ∈ Q ∧ u ∈ x ∧ v ∈ y ∧ w = u + v ) } , u^{*}=\{v\in\mathbb{Q}:v<u\},\qquad x\oplus y=\{w\in\mathbb{Q}:\exists u\,\exists v\,(u\in\mathbb{Q}\wedge v\in\mathbb{Q}\wedge u\in x\wedge v\in y\wedge w=u+v)\}, u ∗ = { v ∈ Q : v < u } , x ⊕ y = { w ∈ Q : ∃ u ∃ v ( u ∈ Q ∧ v ∈ Q ∧ u ∈ x ∧ v ∈ y ∧ w = u + v )} ,
⊖ x = { u ∈ Q : ∃ v ( v ∈ Q ∧ 0 < v ∧ − u − v ∉ x ) } , \ominus x=\{u\in\mathbb{Q}:\exists v\,(v\in\mathbb{Q}\wedge0<v\wedge-u-v\notin x)\}, ⊖ x = { u ∈ Q : ∃ v ( v ∈ Q ∧ 0 < v ∧ − u − v ∈ / x )} ,
x ⊙ y = 0 ∗ ∪ { w ∈ Q : ∃ u ∃ v ( u ∈ Q ∧ v ∈ Q ∧ u ∈ x ∧ v ∈ y ∧ 0 ≤ u ∧ 0 ≤ v ∧ w = u ⋅ v ) } . x\odot y=0^{*}\cup\{w\in\mathbb{Q}:\exists u\,\exists v\,(u\in\mathbb{Q}\wedge v\in\mathbb{Q}\wedge u\in x\wedge v\in y\wedge0\le u\wedge0\le v\wedge w=u\cdot v)\}. x ⊙ y = 0 ∗ ∪ { w ∈ Q : ∃ u ∃ v ( u ∈ Q ∧ v ∈ Q ∧ u ∈ x ∧ v ∈ y ∧ 0 ≤ u ∧ 0 ≤ v ∧ w = u ⋅ v )} .
¶ C C C is a set.
¶ ≤ C \le_{C} ≤ C is a total order on C C C .
¶ u ∗ ∈ C u^{*}\in C u ∗ ∈ C for every u ∈ Q u\in\mathbb{Q} u ∈ Q .
¶ x ⊕ y ∈ C x\oplus y\in C x ⊕ y ∈ C for all x , y ∈ C x,y\in C x , y ∈ C .
¶ ⊖ x ∈ C \ominus x\in C ⊖ x ∈ C for every x ∈ C x\in C x ∈ C .
¶ For every x ∈ C x\in C x ∈ C , 0 ∗ ⊆ x 0^{*}\subseteq x 0 ∗ ⊆ x or 0 ∗ ⊆ ⊖ x 0^{*}\subseteq\ominus x 0 ∗ ⊆ ⊖ x .
¶ If x , y ∈ C x,y\in C x , y ∈ C , 0 ∗ ⊆ x 0^{*}\subseteq x 0 ∗ ⊆ x and 0 ∗ ⊆ y 0^{*}\subseteq y 0 ∗ ⊆ y , then x ⊙ y ∈ C x\odot y\in C x ⊙ y ∈ C and 0 ∗ ⊆ x ⊙ y 0^{*}\subseteq x\odot y 0 ∗ ⊆ x ⊙ y .