Definition:Inverse Relation/Class Theory
Definition
Let $V$ be a basic universe.
Let $A$ and $B$ be subclasses of $V$.
Let $\RR \subseteq A \times B$ be a relation on $A \times B$.
The inverse relation to (or of) $\RR$ is defined as the class of all ordered pairs $\tuple {b, a}$ such that $\tuple {a, b} \in \RR$:
- $\RR^{-1} := \set {\tuple {b, a}: \tuple {a, b} \in \RR}$
Also known as
An inverse relation is also seen as converse relation.
In the context of orderings, the term dual ordering can also be seen.
However, do not confuse this with a dual relation.
Some sources use the notation $\RR^t$, for example T.S. Blyth: Set Theory and Abstract Algebra.
Others use $\breve \RR$, for example Alfred Tarski: Introduction to Logic and to the Methodology of Deductive Sciences (2nd ed.) and 1940: Garrett Birkhoff: Lattice Theory.
Still others use $\RR^\gets$, for example Seth Warner: Modern Algebra.
Also see
- Results about inverse relations can be found here.
Sources
- 2010: Raymond M. Smullyan and Melvin Fitting: Set Theory and the Continuum Problem (revised ed.) ... (previous) ... (next): Chapter $6$: Order Isomorphism and Transfinite Recursion: $\S 1$ A few preliminaries