Transitive relation


Transitive relation

In mathematics, a binary relation "R" over a set "X" is transitive if whenever an element "a" is related to an element "b", and "b" is in turn related to an element "c", then "a" is also related to "c". Transitivity is a key property of both partial order relations and equivalence relations.

Examples

For example, "is greater than," "is at least as great as," and "is equal to" (equality) are transitive relations:

: whenever A > B and B > C, then also A > C: whenever A ≥ B and B ≥ C, then also A ≥ C: whenever A = B and B = C, then also A = C

For some time, economists and philosophers believed that preference was a transitive relation however there are now mathematical theories which demonstrate that preferences and other significant economic results can be modelled without resorting to this assumption.

On the other hand, "is the mother of" is not a transitive relation, because if Alice is the mother of Brenda, and Brenda is the mother of Claire, then Alice is not always the mother of Claire. What is more, it is antitransitive: Alice can "never" be the mother of Claire.

Then again, in biology we often need to consider motherhood over an arbitrary number of generations: the relation "is a matrilinear ancestor of". This "is" a transitive relation. More precisely, it is the transitive closure of the relation "is the mother of".

More examples of transitive relations:
* "is a subset of" (set inclusion)
* "divides" (divisibility)
* "implies" (implication)

Closure properties

The converse of a transitive relation is always transitive: e.g. knowing that "is a subset of" is transitive and "is a superset of" is its converse, we can conclude that the latter is transitive as well.

The intersection of two transitive relations is always transitive: knowing that "was born before" and "has the same first name as" are transitive, we can conclude that "was born before and also has the same first name as" is also transitive.

The union of two transitive relations is not always transitive. For instance "was born before or has the same first name as" is not generally a transitive relation.

The complement of a transitive relation is not always transitive. For instance, while "equal to" is transitive, "not equal to" is only transitive on sets with at most two elements.

Properties of transitivity

For a transitive relation the following are equivalent:
*irreflexivity
*asymmetry
*being a strict partial order

Other properties that require transitivity

* preorder - a reflexive transitive relation
* partial order - an antisymmetric preorder
* total preorder - a total preorder
* equivalence relation - a symmetric preorder
* strict weak ordering - a strict partial order in which incomparability is an equivalence relation
* total ordering - a total, antisymmetric transitive relation

Counting transitive relations

Unlike other relation properties, no general formula that counts the number of transitive relations on a finite set OEIS|id=A006905 is known. [Steven R. Finch, [http://algo.inria.fr/csolve/posets.pdf "Transitive relations, topologies and partial orders"] , 2003.] However, there is a formula for finding the number of relations which are simultaneously reflexive, symmetric, and transitive – in other words, equivalence relations – OEIS|id=A000110, those which are symmetric and transitive, those which are symmetric, transitive, and antisymmetric, and those which are total, transitive, and antisymmetric. Pfeiffer [Götz Pfeiffer, " [http://www.cs.uwaterloo.ca/journals/JIS/VOL7/Pfeiffer/pfeiffer6.html Counting Transitive Relations] ", "Journal of Integer Sequences", Vol. 7 (2004), Article 04.3.2.] has made some progress in this direction, expressing relations with combinations of these properties in terms of each other, but still calculating any one is difficult. See also [Gunnar Brinkmann and Brendan D. McKay," [http://cs.anu.edu.au/~bdm/papers/topologies.pdf Counting unlabelled topologies and transitive relations] "] .

ee also

* transitive closure
* transitive reduction
* intransitivity
* reflexive relation
* symmetric relation
* quasitransitive relation
* relations on sets of two elements and less
*

External links

* [http://www.cut-the-knot.org/triangle/remarkable.shtml Transitivity in Action] at cut-the-knot

References

* "Discrete and Combinatorial Mathematics" - Fifth Edition - by Ralph P. Grimaldi ISBN 0-201-19912-2


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Transitive Relation — Zwei transitive und eine nicht transitive Relation, als gerichtete Graphen dargestellt Die Transitivität einer zweistelligen Relation R auf einer Menge ist gegeben, wenn aus x R y und y R z stets x R z folgt. Man nennt R dann transitiv. Die… …   Deutsch Wikipedia

  • transitive relation — /trænzətɪv rəˈleɪʃən/ (say tranzuhtiv ruh layshuhn) noun Mathematics, Logic a relation which, if it is valid between x and y and between y and z, is also valid between x and z; if …   Australian English dictionary

  • RELATION — Le concept de relation apparaît comme l’un des concepts fondamentaux du discours rationnel. Il semble lié à la pratique de l’analyse, qui constitue elle même l’un des aspects essentiels de la démarche discursive. L’analyse décompose les unités… …   Encyclopédie Universelle

  • Relation transitive — ● Relation transitive relation binaire qui, si elle est vérifiée pour les éléments a et b, ainsi que pour b et c, l est aussi pour a et c …   Encyclopédie Universelle

  • Transitive closure — In mathematics, the transitive closure of a binary relation R on a set X is the smallest transitive relation on X that contains R .For example, if X is a set of airports and xRy means there is a direct flight from airport x to airport y , then… …   Wikipedia

  • Transitive Hülle — Die transitive Hülle bzw. der transitive Abschluss einer (zweistelligen) Relation ist eine Erweiterung dieser Relation, die – vereinfacht gesagt – zusätzlich alle indirekt erreichbaren Paare enthält (und damit transitiv ist). Die transitive Hülle …   Deutsch Wikipedia

  • Transitive reduction — In mathematics, the transitive reduction of a binary relation R on a set X is a minimal relation R on X such that the transitive closure of R is the same as the transitive closure of R . If the transitive closure of R is antisymmetric and finite …   Wikipedia

  • transitive law — Property of relationship that states that if A is in a given relation to B and B is in the same relation to C, then A is also in that relation to C. Equality, for example, is a transitive relation. * * * ▪ logic and mathematics       in… …   Universalium

  • transitive — adjective Etymology: Late Latin transitivus, from Latin transitus, past participle of transire Date: 1590 1. characterized by having or containing a direct object < a transitive verb > < a transitive construction > 2. being or relating to a… …   New Collegiate Dictionary

  • transitive — ● transitif, transitive adjectif (bas latin transitivus, du latin classique transitum, de transire, aller au delà) Se dit d un verbe qui est construit avec un complément d objet direct (transitif direct : « il mange une pomme ») ou un complément… …   Encyclopédie Universelle


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.