=====Directed partial orders===== Abbreviation: **DPO** ====Definition==== A \emph{directed partial order} is a poset $\mathbf{P}=\langle P,\leq \rangle $ that is \emph{directed}, i.e. every finite subset of $P$ has an upper bound in $P$, or equivalently, $P\ne\emptyset$, $\forall xy\exists z (x\le z$ and $y\le z)$. ==Morphisms== Let $\mathbf{P}$ and $\mathbf{Q}$ be directed partial orders. A morphism from $\mathbf{P}$ to $\mathbf{Q}$ is a function $f:Parrow Q$ that is order preserving: $x\le y\Longrightarrow f(x)\le f(y)$ ====Examples==== Example 1: ====Basic results==== ====Properties==== ^[[Classtype]] |first-order | ^[[Amalgamation property]] | | ^[[Strong amalgamation property]] | | ^[[Epimorphisms are surjective]] | | ====Finite members==== $\begin{array}{lr} f(1)= &1\\ f(2)= &1\\ f(3)= &2\\ f(4)= &\\ f(5)= &\\ f(6)= &\\ \end{array}$ ====Subclasses==== [[Directed complete partial orders]] ====Superclasses==== [[Partially ordered sets]] ====References==== [(Ln19xx> )]