Ratz Dratman

I work at a post-secondary institute in Canada and we are developing an educational application using a 3D virtual environment. For copyright and proprietary reasons, we cannot use existing viewers and we are in the process of creating an interface design from scratch that will act as an effective viewer but with the functionality required for our courses. One thing I have noticed though, is that many of the viewers - both from SL as well as 3rd party - seem to have many commonalities such as tabs along the top and bottom, inventory tab on the bottom right, left click on the mouse for some interactions, right click for others....roll forward for mouseview etc... Can anyone here describe the reasoning and logic behind their viewer decisions and whether there is any type of research that explains why certain tabs and functions are the way they are? Thanks