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A preorder that is antisymmetric no longer has cycles; it is a partial order, and corresponds to a directed acyclic graph. A preorder that is symmetric is an equivalence relation; it can be thought of as having lost the direction markers on the edges of the graph.
Conversely, a strict partial order < on may be converted to a non-strict partial order by adjoining all relationships of that form; that is, := < is a non-strict partial order. Thus, if ≤ {\displaystyle \leq } is a non-strict partial order, then the corresponding strict partial order < is the irreflexive kernel given by a < b if a ≤ b and a ...
Many important examples of directed sets can be defined using these partial orders. For example, by definition, a prefilter or filter base is a non-empty family of sets that is a directed set with respect to the partial order and that also does not contain the empty set (this condition prevents triviality because otherwise, the empty set would ...
A total order is a total preorder which is antisymmetric, in other words, which is also a partial order. Total preorders are sometimes also called preference relations . The complement of a strict weak order is a total preorder, and vice versa, but it seems more natural to relate strict weak orders and total preorders in a way that preserves ...
A preorder is a reflexive and transitive relation. The difference between a preorder and a partial-order is that a preorder allows two different items to be considered "equivalent", that is, both and hold, while a partial-order allows this only when =.
The Dedekind–MacNeille completion may be exponentially larger than the partial order it comes from, [12] and the time bounds for such algorithms are generally stated in an output-sensitive way, depending both on the number n of elements of the input partial order, and on the number c of elements of its completion.
While between partial orders it is usual to consider order-preserving functions, the most important type of functions between prefix orders are so-called history preserving functions. Given a prefix ordered set P , a history of a point p ∈ P is the (by definition totally ordered) set p − = { q | q ≤ p }.
The "induced concept lattice is isomorphic to the cut completion of the partial order that belongs to the minimal decomposition (,,) of the relation ." Particular cases are considered below: E {\displaystyle E} total order corresponds to Ferrers type, and E {\displaystyle E} identity corresponds to difunctional, a generalization of equivalence ...