These are two programs to build a "semacarte" (a mindmap). Though they provide more flexibility they may take more time to use than other programs with graphical interfaces.
Poseidon is for mindmaps in general, while Apollo focuses on writing code.

Skip the learning curve and "just model" with Poseidon

Don't lose the advantage of clarity and simplicity to an overly complicated tool - the Poseidon for UML software line lets you get down to work without entanglements in your development environment.  Powerful features such as round trip engineering and documentation generation have been intelligently implemented without the overhead common to so many other UML tools on the market today.

Download here: http://www.gentleware.com/downloadcenter.html

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