draw uml with latex&metauml

I've used and enjoyed the benefits of reversion control system for several years. RCS makes my life a lot easier. And it pushes me to highly prefer text format files over binary files, because text files can be managed by RCS more easily. metauml is a metapost library for creating uml diagrams, in text format.

Here are the steps to use it on ubuntu:

1. install texlive with: sudo apt-get install texlive
2. install metauml containing in metapost for tex: sudo apt-get install texlive-metapost

Texlive is also available for windows.
After all these tools have being installed, we can start our first uml diagram in latex.
Suppose we have following classes, and want to draw class diagram for them.

 1 class Point
 2 {
 3 public:
 4     int x;
 5     int y;
 6 };
 7 
 8 class Shape
 9 {
10     public:
11         virtual int get_circumference() = 0;
12         virtual ~shape();
13 };
14 
15 class Circle : public Shape
16 {
17     private:
18         Point center;
19         int radius;
20     public:
21         int get_circumference();
22 };

We create below metapost file, save it as class_diagram.mp, and use "mpost class_diagram.mp" command to generate a postscript file, class_diagram.1.

 1 input metauml;
 2 beginfig(1);
 3     %define classes
 4     Class.Point("Point")("+x: int", "+y: int")();
 5     Class.Shape("Shape")()("+get_circumference(): int");
 6     Class.Circle("Circle")("-center: Point", "-radius:  int")("+get_circumference(): int");
 7
 8     %layout classes
 9     topToBottom(50)(Point, Circle);
10     leftToRight(50)(Circle, Shape);
11 
12     %draw classes
13     drawObjects(Point, Shape, Circle);
14 
15     %link classes
16     link(inheritance)(Circle.e -- Shape.w);
17     link(composition)(Point.s -- Circle.n);
18 endfig;
19 end
20 

 Then we create below tex file as a container document for the postscript. And use "pdflatex uml.tex" to generate the final pdf file.

 1 \documentclass{article}
 2 
 3 % The following is needed in order to make the code compatible
 4 % with both latex/dvips and pdflatex.
 5 \ifx\pdftexversion\undefined
 6 \usepackage[dvips]{graphicx}
 7 \else
 8 \usepackage[pdftex]{graphicx}
 9 \DeclareGraphicsRule{*}{mps}{*}{}
10 \fi
11 
12 \title{MetaUML example}
13 \author{Raymond Wen}
14 
15 \begin{document}
16 
17 \maketitle
18 
19 \section{Example}
20 \includegraphics{class_diagram.1}
21 
22 \end{document}

A thing worth noticing is the latex document is of A4 size by default, which is not possible to contain a complex uml diagram. We can use "\paperwidth = 1024pt", "\paperheight = 1024pt", "\textheight = 800pt" command to create a document of arbitrary size. Here is more information about latex page layout.
The final diagram is shown below:

The advantages of using tex file to draw uml diagram includes:

1. We can concentrate on the content of the uml, rather than its layout
2. The diagram can be easily version controlled and compared
3. It's easier to make modifications
4. It's totally free
5. The output file format can be easily changed
6. It's possible to use/write tools to generate uml diagram automatically