Clonal sets of a binary relation
Published in International Journal of General Systems, 2018
Lemnaouar Zedam, Raúl Pérez-Fernández, Hassane Bouremel, Bernard De Baets
A (non-empty) poset is called a lattice if any two elements x and y have a greatest lower bound, denoted by and called the infimum of x and y, and a smallest upper bound, denoted by and called the supremum of x and y. Similarly, a lattice is called complete if every subset A of L has both a greatest lower bound, denoted by and called the infimum of A, and a smallest upper bound, denoted by and called the supremum of A. A lattice is called bounded if it has a smallest and a greatest element, respectively denoted by 0 and 1. A non-empty subset M of a lattice is called a sublattice of L if, for any , it holds that and . A complemented lattice is a bounded lattice in which any element x has a complement, i.e. there exists an element such that and . The relevant notions of distributivity and modularity of a lattice are characterized by means of the lattices and illustrated in Figure 5. In particular, a lattice is modular if and only if it has no sublattice of the form , and distributive if and only if it has no sublattice of the form or . For more details, we refer to Davey and Priestley (2002).