or ▁real ▁world ▁object ). ▁T ables ▁are ▁known ▁as ▁collections ▁in ▁Small world ▁parl ance . ▁▁▁ ▁# ▁all _ rw os ▁hold ▁all ▁the ▁rows ▁in ▁the ▁database ▁and ▁is ▁heter ogeneous ▁▁ ▁all _ rw os ▁<< ▁my _ application . r wo _ set () ▁▁▁▁ ▁# ▁val ve _ collection ▁holds ▁the ▁val ve ▁collection ▁▁ ▁val ves ▁<< ▁all _ rw os . select (: collection , ▁{: val ve }) ▁▁ ▁number _ of _ val ves ▁<< ▁val ves . size ▁ ▁Qu eries ▁are ▁built ▁up ▁using ▁predicate ▁objects : ▁▁▁ ▁# ▁find ▁' open ' ▁val ves . ▁▁ ▁open _ val ves ▁<< ▁val ves . select ( pred icate . eq (: oper ating _ status , ▁" open ")) ▁▁ ▁number _ of _ open _ val ves ▁<< ▁open _ val ves . size ▁▁▁ ▁_ for ▁val ve ▁_ over ▁open _ val ves . elements () ▁▁ ▁_ loop ▁▁▁▁ ▁write ( val ve . id ) ▁▁ ▁_ end loop ▁ ▁Jo ins ▁are ▁implemented ▁as ▁methods ▁on ▁the ▁parent ▁R W O . ▁For ▁example , ▁a ▁manager ▁might ▁have ▁several ▁employees ▁who ▁report ▁to ▁him : ▁▁▁ ▁# ▁get ▁the ▁employee ▁collection . ▁▁ ▁employees ▁<< ▁my _ application . database . collection (: g is , ▁: emp loy ees ) ▁▁▁ ▁# ▁find ▁a ▁manager ▁called ▁' Ste ve ' ▁and ▁get ▁the ▁first ▁matching ▁element ▁▁ ▁ste ve ▁<< ▁employees .