Thanks for providing this document. I still wading my way through it but it's nice to have such in-depth information. Thanks also to Damien for including it in squeak-dev, which is shaping up very nicely! However, I have a problem which may or may not be related but it seemed to appear after I installed OB. On opening "image browser" or indeed "class browser" I get "MessageNotUnderstood: Array>>similarSpeciesInstance:". As far as I can tell "similarSpeciesInstance:" was added some time ago but I suspect also that other things I have installed may have removed/over-written it. Any tips on how this problem has arisen and what to do about it?