diff --git a/doc/.gitignore b/doc/.gitignore
new file mode 100644
index 00000000..24600083
--- /dev/null
+++ b/doc/.gitignore
@@ -0,0 +1 @@
+!Makefile
diff --git a/doc/Makefile b/doc/Makefile
new file mode 100644
index 00000000..7c515864
--- /dev/null
+++ b/doc/Makefile
@@ -0,0 +1,4 @@
+all: class-diagram.png collaboration.png communication-sequence-normal.png
+%.png: %.dia
+	dia -e $@ $<
+	-optipng $@ -out tmp$@ && mv tmp$@ $@
diff --git a/doc/class-diagram.png b/doc/class-diagram.png
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index 00000000..6bd09b89
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diff --git a/doc/collaboration.png b/doc/collaboration.png
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index 00000000..7049ea3d
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diff --git a/doc/communication-sequence-normal.png b/doc/communication-sequence-normal.png
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index 00000000..8d6d2374
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