▁that ▁these ▁are ▁not ▁limited ▁to ▁the ▁standards ▁for ▁ISO , ▁Microsoft , ▁or ▁D CE ▁U UID s ▁though ▁those ▁are ▁examples ▁of ▁acceptable ▁sources ▁of ▁U UID s . ▁ ▁Attribute ▁names ▁are ▁case - fold ed ▁and ▁normal ized ▁strings ▁of ▁Unicode ▁characters ▁ ▁Val ues ▁are ▁arbitrary - length ▁arrays ▁of ▁bytes ▁( B LOB s , ▁though ▁not ▁necessary ▁" large ") ▁ ▁Each ▁attribute ▁has ▁only ▁one ▁value ▁( though ▁the ▁bytes ▁may ▁be ▁interpreted ▁to ▁represent ▁a ▁vector ▁of ▁data ) ▁ ▁The ▁number ▁of ▁attribute - value ▁pairs ▁is ▁arbitrary ▁and ▁extens ible ▁at ▁any ▁time ▁ ▁The ▁attribute - value ▁pairs ▁are ▁treated ▁as ▁a ▁set ▁( i . e ., ▁they ▁are ▁un ordered ) ▁ ▁Copy ing ▁vs ▁Rep lication ▁▁ ▁An ▁important ▁characteristic ▁of ▁u - forms , ▁of ▁significance ▁to ▁distributed ▁database ▁systems , ▁is ▁that ▁they ▁support ▁a ▁clear ▁distinction ▁between ▁copying ▁and ▁rep lication ▁of ▁data ▁objects . ▁Copy ing ▁a ▁u - form ▁involves ▁the ▁creation ▁of ▁a ▁new ▁u - form ▁( i . e ., ▁one ▁with ▁a ▁different ▁U UID ), ▁but ▁with ▁all ▁attribute - value ▁pairs ▁identical ▁to ▁those ▁of ▁the ▁original ▁u - form . ▁▁ ▁Rep lic ating ▁a ▁u - form ▁involves ▁creating ▁a ▁new ▁instance ▁of ▁the ▁u - form ▁with ▁the ▁same ▁U UID ▁as ▁the ▁original . ▁▁ ▁Note ▁that ▁in ▁a ▁distributed ▁system , ▁two ▁instances ▁of ▁the ▁same ▁u - form ▁may ▁be ▁incons