ology ▁Library ▁maintain s ▁a ▁legacy ▁of ▁ont ologies ▁in ▁DA ML . ▁ ▁Ont ology ▁Design ▁Pattern s ▁portal ▁is ▁a ▁w iki ▁repository ▁of ▁re usable ▁components ▁and ▁practices ▁for ▁ont ology ▁design , ▁and ▁also ▁maintain s ▁a ▁list ▁of ▁exempl ary ▁ont ologies . ▁▁ ▁Pro t ég é ▁Ont ology ▁Library ▁contains ▁a ▁set ▁of ▁O W L , ▁Frame - based ▁and ▁other ▁format ▁ont ologies . ▁ ▁Sch ema Web ▁is ▁a ▁directory ▁of ▁R DF ▁sch em ata ▁expressed ▁in ▁R DF S , ▁O W L ▁and ▁DA ML + O IL . ▁ ▁The ▁following ▁are ▁both ▁directories ▁and ▁search ▁engines . ▁ ▁O BO ▁Found ry ▁is ▁a ▁suite ▁of ▁inter oper able ▁reference ▁ont ologies ▁in ▁bi ology ▁and ▁bi om edic ine . ▁ ▁Bi oport al ▁( ont ology ▁repository ▁of ▁NC BO ) ▁ ▁On to Select ▁Ont ology ▁Library ▁offers ▁similar ▁services ▁for ▁R DF / S , ▁DA ML ▁and ▁O W L ▁ont ologies . ▁ ▁Ont aria ▁is ▁a ▁" search able ▁and ▁brow s able ▁directory ▁of ▁semantic ▁web ▁data " ▁with ▁a ▁focus ▁on ▁R DF ▁voc ab ular ies ▁with ▁O W L ▁ont ologies . ▁( NB ▁Project ▁" on ▁hold " ▁since ▁ 2 0 0 4 ). ▁ ▁S wo ogle ▁is ▁a ▁directory ▁and ▁search ▁engine ▁for ▁all ▁R DF ▁resources ▁available ▁on ▁the ▁Web , ▁including ▁ont ologies . ▁ ▁Open ▁Ont ology ▁Re pository ▁initi