Attached Link: Kerkythea

*"Anyone can tell me where I can find skp file format specification or documentation?"*

You might check with the Kerkythea folks. Someone there wrote a SketchUp to Kerkythea plugin for SketchUp. Don't know how much help that might be for a standalone or a Poser plugin though if that's what you have in mind.

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken