▁data , ▁de - ident ification ▁is ▁sometimes ▁required ▁and ▁often ▁used ▁for ▁data ▁priv acy ▁when ▁users ' ▁personal ▁data ▁are ▁collected ▁by ▁companies ▁or ▁third - party ▁organizations ▁who ▁will ▁analyze ▁it ▁for ▁their ▁own ▁personal ▁usage . ▁ ▁In ▁smart ▁cities , ▁de - ident ification ▁may ▁be ▁required ▁to ▁protect ▁the ▁priv acy ▁of ▁residents , ▁workers ▁and ▁visitors . ▁Without ▁strict ▁reg ulation , ▁de - ident ification ▁may ▁be ▁difficult ▁as ▁sens ors ▁can ▁collect ▁information ▁without ▁consent . ▁ ▁Lim its ▁When ever ▁a ▁person ▁particip ates ▁in ▁gen et ics ▁research ▁the ▁don ation ▁of ▁a ▁bi ological ▁spec imen ▁often ▁results ▁in ▁the ▁creation ▁of ▁a ▁large ▁amount ▁of ▁personal ized ▁data . ▁Such ▁data ▁is ▁uniqu ely ▁difficult ▁to ▁de - ident ify . ▁ ▁An onym ization ▁of ▁gen etic ▁data ▁is ▁particularly ▁difficult ▁because ▁of ▁the ▁huge ▁amount ▁of ▁gen ot yp ic ▁information ▁in ▁b ios pec im ens , ▁the ▁t ies ▁that ▁spec im ens ▁often ▁have ▁to ▁medical ▁history , ▁and ▁the ▁advent ▁of ▁modern ▁bio in format ics ▁tools ▁for ▁data ▁min ing . ▁There ▁have ▁been ▁demonstr ations ▁that ▁data ▁for ▁individuals ▁in ▁aggregate ▁collections ▁of ▁gen ot yp ic ▁data ▁sets ▁can ▁be ▁tied ▁to ▁the ▁ident ities ▁of ▁the ▁spec imen ▁don ors . ▁ ▁Some ▁research ers ▁have ▁suggested ▁that ▁it ▁is ▁not ▁reasonable ▁to ▁ever ▁promise ▁participants ▁in ▁gen et ics ▁research ▁that ▁they ▁can ▁retain ▁their ▁an onym ity ,