Now defunct.[47] photo.net An online photography resource and community, designed and founded by Philip Greenspun.[48] Greenspun released the software behind photo.net as a free open-source toolkit for building community websites, the ArsDigita Community System.[49] Principia Cybernetica Probably the first complex, collaborative knowledge system, sporting a hierarchical structure, index, map, annotations, search, plenty of hyperlinks, etc.