Extending Dia

[Fermín Galán Márquez <fermin galan agora-2000 com>]

Hello,

This is a quite devel question, so I don't know if this list is the 
right place. That case, please forgive me :).

I'm planning extending Dia with an additional diagram type (like the 
ones for flow charts or UML). I would like to know if there is an API, 
interface or similar for extending dia with new diagramas types (in that 
case, any information about how to use it it's really welcome). In 
addition, I would like to know a bit more about the XML Dia file format 
(due to the extension that I'm planning will need to store information 
associated to the drawing attributes, in a similar way that UML does). 
Is there any DTD or XML Schema for that?

Thanks in advance and Merry Christmas!

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Fermín