▁has ▁also ▁been ▁defined ▁more ▁recently ▁in ▁terms ▁of ▁us ability ; ▁what ▁must ▁a ▁data ▁grid ▁be ▁able ▁to ▁do ▁in ▁order ▁for ▁it ▁to ▁be ▁useful ▁to ▁the ▁scientific ▁community . ▁Pro ponents ▁of ▁this ▁theory ▁arrived ▁at ▁several ▁criteria . ▁One , ▁users ▁should ▁be ▁able ▁to ▁search ▁and ▁discover ▁applicable ▁resources ▁within ▁the ▁data ▁grid ▁from ▁amongst ▁its ▁many ▁datasets . ▁Two , ▁users ▁should ▁be ▁able ▁to ▁locate ▁datasets ▁within ▁the ▁data ▁grid ▁that ▁are ▁most ▁suitable ▁for ▁their ▁requirement ▁from ▁amongst ▁numerous ▁rep lic as . ▁Three , ▁users ▁should ▁be ▁able ▁to ▁transfer ▁and ▁move ▁large ▁datasets ▁between ▁points ▁in ▁a ▁short ▁amount ▁of ▁time . ▁Four , ▁the ▁data ▁grid ▁should ▁provide ▁a ▁means ▁to ▁manage ▁multiple ▁copies ▁of ▁datasets ▁within ▁the ▁data ▁grid . ▁And ▁finally , ▁the ▁data ▁grid ▁should ▁provide ▁security ▁with ▁user ▁access ▁controls ▁within ▁the ▁data ▁grid , ▁i . e . ▁which ▁users ▁are ▁allowed ▁to ▁access ▁which ▁data . ▁ ▁The ▁data ▁grid ▁is ▁an ▁evol ving ▁technology ▁that ▁continues ▁to ▁change ▁and ▁grow ▁to ▁meet ▁the ▁needs ▁of ▁an ▁expand ing ▁community . ▁One ▁of ▁the ▁earliest ▁programs ▁begun ▁to ▁make ▁data ▁gr ids ▁a ▁reality ▁was ▁fund ed ▁by ▁the ▁Def ense ▁Advanced ▁Research ▁Project s ▁Agency ▁( D AR PA ) ▁in ▁ 1 9 9 7 ▁at ▁the ▁University ▁of ▁Chicago . ▁This ▁research ▁spawn ed ▁by ▁D AR PA ▁has ▁continued ▁down ▁the ▁path ▁to ▁creating ▁open ▁source ▁tools ▁that ▁make ▁data ▁gr