=====Reflexive relations===== Abbreviation: **RefRel** ====Definition==== A \emph{reflexive relation} is a structure $\mathbf{X}=\langle X,R\rangle$ such that $R$ is a \emph{binary relation on $X$} (i.e. $R\subseteq X\times X$) that is reflexive: $xRx$ ==Morphisms== Let $\mathbf{X}$ and $\mathbf{Y}$ be reflexive relations. A morphism from $\mathbf{X}$ to $\mathbf{Y}$ is a function $h:A\rightarrow B$ that is a homomorphism: $xR^{\mathbf X} y\Longrightarrow h(x)R^{\mathbf Y}h(y)$ ====Definition==== ====Examples==== Example 1: ====Basic results==== ====Properties==== Feel free to add or delete properties from this list. The list below may contain properties that are not relevant to the class that is being described. ^[[Classtype]] |variety | ^[[Equational theory]] |decidable | ^[[First-order theory]] | | ^[[Locally finite]] |yes | ^[[Residual size]] | | ^[[Congruence distributive]] |no | ^[[Congruence modular]] |no | ^[[Congruence $n$-permutable]] | | ^[[Congruence regular]] | | ^[[Congruence uniform]] | | ^[[Congruence extension property]] | | ^[[Definable principal congruences]] | | ^[[Equationally def. pr. cong.]] | | ^[[Amalgamation property]] | | ^[[Strong amalgamation property]] | | ^[[Epimorphisms are surjective]] | | ====Finite members==== $\begin{array}{lr} f(1)= &1\\ f(2)= &\\ f(3)= &\\ f(4)= &\\ f(5)= &\\ \end{array}$ $\begin{array}{lr} f(6)= &\\ f(7)= &\\ f(8)= &\\ f(9)= &\\ f(10)= &\\ \end{array}$ ====Subclasses==== ====Superclasses==== [[Directed graphs]] supervariety ====References==== [(Lastname19xx> F. Lastname, \emph{Title}, Journal, \textbf{1}, 23--45 [[MRreview]] )]