Hi,
I've been working in following project related to editing UML diagrams from web (this project is mainly aimed at wiki)
you can find more info from: http://carlosmanzanares.com/blog/?cat=3 (contains videos/screenshots/distributable)
direct link to running Web20 application: http://www.carlosmanzanares.com/uml/sandbox/uml.html
regards,
--Carlos--
p.s.: @Nicola: it seems I should have checked these forums earlier, I only noticed now that you have been doing something quite similar (not sure what is the progress of your app)

Hi Carlos, I temporarily
Hi Carlos,
I temporarily stopped my work on the "diagramming tool" because I'm writing another widget in which I will try to integrate it
You find a first work in progress at:
http://nicolarizzo.altervista.org/trunk/demos/gfx/dojoUml.html
Regards,
nic
References
Hi Nic,
I'm building a UI which will require some similar functionality (i.e. connecting shapes with arrows). Can you point me to any references, tutorials or examples that you found helpful in building your UML tool?
Thanks.
Hi Abe, my diagram is based
Hi Abe,
my diagram is based on the "circles demo". I wrote the other functionalities from scratch.
You can download it if you want; I'm writing another widget now, but I'll work on the blockdiagram as soon as possible.
Regards,
nic
Hi Nic, I would love to
Hi Nic,
I would love to download it but I can't figure out where to get it from. I stumbled across your website but couldn't find a download there or at the altervista site. Can you please send me a link? Thank so much.
zipped source
http://www.nicolarizzo.com/gamesroom/downloads/diagram_dojo043.zip
Tell me if you need help.
nic
I'll make a zip file
I'll make a zip file containing dojo0.4.3+blockdiagram tomorrow, ok?
You can write your own blocks and connectors (they are widgets) using my block diagram: a connector can have less than 100 lines of code, via inheritance.
I release my code under GPL.
nic