▁Material ▁Buck ling ▁in ▁nuclear ▁react ors ▁ ▁See ▁also ▁ ▁Buck le ▁( disambiguation ) ▁ ▁Sun ▁k ink ▁of ▁railway ▁rails <0x0A> </s> ▁R DF a ▁( or ▁Resource ▁Description ▁Framework ▁in ▁Att ributes ) ▁is ▁ ▁a ▁W 3 C ▁Re comm end ation ▁that ▁adds ▁a ▁set ▁of ▁attribute - level ▁extensions ▁to ▁HTML , ▁X HTML ▁and ▁various ▁XML - based ▁document ▁types ▁for ▁embedding ▁rich ▁metadata ▁within ▁Web ▁documents . ▁The ▁R DF ▁data - model ▁mapping ▁enables ▁its ▁use ▁for ▁embedding ▁R DF ▁subject - pred icate - object ▁expressions ▁within ▁X HTML ▁documents . ▁It ▁also ▁enables ▁the ▁extra ction ▁of ▁R DF ▁model ▁tri ples ▁by ▁comp li ant ▁user ▁agents . ▁ ▁The ▁R DF a ▁community ▁runs ▁a ▁w iki ▁website ▁to ▁host ▁tools , ▁examples , ▁and ▁tutorials . ▁ ▁History ▁ ▁R DF a ▁was ▁first ▁proposed ▁by ▁Mark ▁Bir beck ▁in ▁the ▁form ▁of ▁a ▁W 3 C ▁note ▁entitled ▁X HTML ▁and ▁R DF , ▁which ▁was ▁then ▁presented ▁to ▁the ▁Sem antic ▁Web ▁Interest ▁Group ▁at ▁the ▁W 3 C ' s ▁ 2 0 0 4 ▁Techn ical ▁Pl en ary . ▁Later ▁that ▁year ▁the ▁work ▁became ▁part ▁of ▁the ▁sixth ▁public ▁Working ▁D raft ▁of ▁X HTML ▁ 2 . 0 . ▁Although ▁it ▁is ▁generally ▁assumed ▁that ▁R DF a ▁was ▁originally ▁intended ▁only ▁for ▁X HTML ▁ 2 , ▁in ▁fact ▁the ▁purpose ▁of ▁R DF a ▁was ▁always ▁to ▁provide ▁a