Cheers - will have a search around rigging/skeleton/degrees of freedom and see what I can find. (I think 'rigging' was the word I was looking for, although I want a simple 2d case and inthe case of ambiguity as to how the skeleton moves when I drag one of the joints, I do not care so much how this is resolved so long as it "feels" natural.
I suppose one way to address the ambiguity alvinpenner mentioned would be to pick some (fairly arbitrary) direction along which "gravity" is applied. Which brings me back to a 2D physics engine, I think).
I am just trying to write an Inkscape extension for drawing crochet diagrams (!), and there is a use case where you might have a "string" of stitches laid out into some particular shape an you want to adjust this shape, keeping the string (and stitches) the same length and size - that is, each stitch has a fixed size an each stitch is connected to the stitch next to it. I had the idea of representing the pattern where the stitches are nodes along a path (that way not only do I get the shape all the stitches together should make, but the use of a path with nodes gives me the *order* the stitches are done in so that I can generate a word pattern from a diagram).