▁specify ▁the ▁mean ings ▁of ▁the ▁domain ▁ont ology ▁entities ▁can ▁be ▁merged ▁with ▁less ▁effort . ▁There ▁are ▁studies ▁on ▁generalized ▁techniques ▁for ▁mer ging ▁ont ologies , ▁but ▁this ▁area ▁of ▁research ▁is ▁still ▁on going , ▁and ▁it ' s ▁a ▁recent ▁event ▁to ▁see ▁the ▁issue ▁sid este pped ▁by ▁having ▁multiple ▁domain ▁ont ologies ▁using ▁the ▁same ▁upper ▁ont ology ▁like ▁the ▁O BO ▁Found ry . ▁ ▁Upper ▁ont ology ▁▁ ▁An ▁upper ▁ont ology ▁( or ▁foundation ▁ont ology ) ▁is ▁a ▁model ▁of ▁the ▁common ▁relations ▁and ▁objects ▁that ▁are ▁generally ▁applicable ▁across ▁a ▁wide ▁range ▁of ▁domain ▁ont ologies . ▁It ▁usually ▁emp lo ys ▁a ▁core ▁gl oss ary ▁that ▁contains ▁the ▁terms ▁and ▁associated ▁object ▁descri ptions ▁as ▁they ▁are ▁used ▁in ▁various ▁relevant ▁domain ▁ont ologies . ▁ ▁Standard ized ▁upper ▁ont ologies ▁available ▁for ▁use ▁include ▁B FO , ▁BO RO ▁method , ▁Dublin ▁Core , ▁G FO , ▁Cy c , ▁SUM O , ▁U MB EL , ▁the ▁Un ified ▁Found ational ▁Ont ology ▁( U FO ), ▁and ▁D OL CE . ▁Word Net ▁has ▁been ▁considered ▁an ▁upper ▁ont ology ▁by ▁some ▁and ▁has ▁been ▁used ▁as ▁a ▁lingu istic ▁tool ▁for ▁learning ▁domain ▁ont ologies . ▁ ▁Hy brid ▁ont ology ▁ ▁The ▁G ell ish ▁ont ology ▁is ▁an ▁example ▁of ▁a ▁combination ▁of ▁an ▁upper ▁and ▁a ▁domain ▁ont ology . ▁ ▁Visual ization ▁ ▁A ▁survey ▁of ▁ont ology ▁visual ization ▁methods