: 2 0 0 1 ▁death s ▁Category : Play ers ▁of ▁American ▁football ▁from ▁Illinois ▁Category : American ▁football ▁ends ▁Category : Miss iss ippi ▁State ▁Bul ld ogs ▁football ▁players ▁Category : New ▁York ▁Gi ants ▁players ▁Category : American ▁military ▁personnel ▁of ▁World ▁War ▁II ▁Category : S ports people ▁from ▁Chicago <0x0A> </s> ▁In ▁computer ▁science , ▁a ▁U - form ▁is ▁an ▁abstract ▁data ▁type ▁compr ising ▁a ▁collection ▁of ▁attribute - value ▁pairs ▁associated ▁with ▁a ▁univers ally - unique ▁identifier ▁( U UID ). ▁ ▁A ▁U - form ▁essentially ▁compr ises ▁an ▁associ ative ▁array ▁augment ed ▁with ▁a ▁U UID ▁and ▁with ▁keys ▁limited ▁to ▁strings . ▁ ▁The ▁U UID ▁that ▁is ▁associated ▁with ▁a ▁u - form ▁is ▁imm utable , ▁however ▁all ▁data ▁" cont ained " ▁in ▁the ▁u - form ▁are ▁mutable ▁( including ▁the ▁keys / names ). ▁ ▁The ▁mut ability ▁of ▁contained ▁data ▁combined ▁with ▁an ▁imm utable ▁identifier ▁make ▁implementations ▁of ▁fully ▁mutable , ▁rep lic able ▁digital ▁objects ▁possible . ▁This ▁has ▁applications ▁in ▁distributed ▁computing , ▁non - rel ational ▁database ▁systems , ▁information ▁visual ization , ▁and ▁knowledge ▁representation ▁systems . ▁ ▁N avig ational ▁databases , ▁Entity ▁and ▁associ ative ▁entity ▁relationships ▁can ▁be ▁implemented ▁by ▁using ▁a ▁U UID , ▁or ▁multiple ▁U UID s , ▁as ▁attribute ▁values . ▁ ▁The ▁u - form ' s ▁design ▁goals ▁center ▁around ▁supporting ▁an ▁open , ▁extens ible ▁distributed ▁information ▁space