+-----------------+       +--------+           +--------------------+
| markdown source |------>| ppp    |------*--->| pröcessed markdown |
+-----------------+       +--------+      |    +--------------------+
                              |           \--->| image files        |
                    +------------------+       +--------------------+
                    | diagram creation |
                    +------------------+
                    | ditaa/dot/rdfdot |
                    +------------------+
