UML Diagrams

You can use Graphviz's Dot package to create UML diagrams.

Examples

Simple Class

You can make a simple class UML diagram like this:

<graphviz> digraph G { rankdir="LR" node [shape=record]; Arches [shape=record,label="<f0> Arches | <f1> problemSetup() : void \\ \lscheduleInitialize() : void \\ \linitialize() : void \\ \lscheduleComputeStableTimestep() : void \\ \lcomputeStableTimestep() : void \\ \lscheduleTimeAdvance() : void \\ \ltimeAdvance() : void \\ | \\ <f2> sharedState_ : SimulationState \\ \lmyMaterial_ : Material \\ "]; } </graphviz>

<graphviz> digraph G { rankdir="LR" node [shape=record]; Arches [shape=record,label="<f0> Arches | <f1> problemSetup() : void \\ \lscheduleInitialize() : void \\ \linitialize() : void \\ \lscheduleComputeStableTimestep() : void \\ \lcomputeStableTimestep() : void \\ \lscheduleTimeAdvance() : void \\ \ltimeAdvance() : void \\

\\ <f2> sharedState_ : SimulationState \\ \lmyMaterial_ : Material \\ "]; } </graphviz>

Inheritance Diagram

Class inheritance can be illustrated with a UML diagram with a black arrow pointing from the child to the parent.

This code: <graphviz> digraph G { node [shape=record]; BaseClass [shape=record,label="{<f0> BaseClass \\ | <f1> + doSomething() : void \\ }"]; DerivedClass [shape=record,label="{<f0> ScalarEqn \\ | <f1> + doSomethingDerived() : void \\ }"]; BaseClass->DerivedClass [dir=back]; } </graphviz>

Makes this diagram: <graphviz> digraph G { node [shape=record]; BaseClass [shape=record,label="{<f0> BaseClass \\

<f1> + doSomething() : void \\ }"]; DerivedClass [shape=record,label="{<f0> ScalarEqn \\

<f1> + doSomethingDerived() : void \\ }"]; BaseClass->DerivedClass [dir=back]; } </graphviz>

Composition & Aggregation

Composition

Composition is a strong relationship between two entities, usually linked strongly by lifecycle. To say "an instance of class A MUST have an instance of class B" means that B composes A. It is a 1-to-1 (or 1-to-N) relationship. Think of a situation where you call class A's constructor, and class A's constructor calls class B's constructor; and vice-versa with the destructor (A's destructor calls B's destructor).

A concrete example would be a car and an engine. The two are related by composition: there is a strong lifecycle dependency between the two, and the relationship is 1-to-1.

Composition can be illustrated in a UML diagram as follows:

<graphviz> digraph G { node [shape=record]; Car [shape=record,label="Car"]; Engine [shape=record,label="Engine"]; Car->Engine [dir=back]; } </graphviz> </graphviz>

<graphviz> digraph G { node [shape=record]; Car [shape=record,label="Car"]; Engine [shape=record,label="Engine"]; Car->Engine [dir=back,arrowtail="diamond"]; } </graphviz>

And if you want you can even describe the relationship by adding head and tail labels, following http://en.wikipedia.org/wiki/Class_diagram :

<graphviz> digraph G { node [shape=record]; Car [shape=record,label="Car"]; Engine [shape=record,label="Engine"]; Car->Engine [dir=back,arrowtail="diamond"]; } </graphviz>

<graphviz> digraph G { node [shape=record]; Car [shape=record,label="Car"]; Engine [shape=record,label="Engine"]; Car->Engine [dir=back,arrowtail="diamond",headlabel="1..1",label=" ",taillabel="1..1"]; } </graphviz>

Aggregation

Aggregation is a weaker, many-to-many relationship: for example, ducks and ponds. There is not necessarily a strong lifecycle dependency between the two classes, and it represents a relationship best described as "is part of": "class B is part of class A".

<graphviz> digraph G { node [shape=record]; Duck [shape=record,label="Duck"]; Pond [shape=record,label="Pond"]; Duck->Pond [dir=back,arrowtail="odiamond"]; } </graphviz>

<graphviz> digraph G { node [shape=record]; Duck [shape=record,label="Duck"]; Pond [shape=record,label="Pond"]; Duck->Pond [dir=back,arrowtail="odiamond"]; } </graphviz>

And again modifying the head and tail to show more information about the relationship is possible:

<graphviz> digraph G { node [shape=record]; Duck [shape=record,label="Duck"]; Pond [shape=record,label="Pond"]; Duck->Pond [dir=back,arrowtail="odiamond",taillabel="1..*",label=" ",headlabel="1..*"]; } </graphviz>

<graphviz> digraph G { node [shape=record]; Duck [shape=record,label="Duck"]; Pond [shape=record,label="Pond"]; Duck->Pond [dir=back,arrowtail="odiamond",taillabel="1..*",label=" ",headlabel="1..*"]; } </graphviz>