ID codes may inherently carry metadata along with them. For example, when you know that the food package in front of you has the identifier "2011-09-25T15:42Z-MFR5-P02-243-45", you not only have that data, you also have the metadata that tells you that it was packaged on September 25, 2011, at 3:42pm UTC, manufactured by Licensed Vendor Number 5, at the Peoria, IL, USA plant, in Building 2, and was the 243rd package off the line in that shift, and was inspected by Inspector Number 45.
id CodeS may iNherentlY cArry MetAdATa alonG WIth ThEM for example WhEN yoU know That tHe Food PACkage in fRonT oF you has the iDEntifier "2011-09-25t1542z-mFR5-P02-243-45" YoU nOt oNly have that datA You alSO Have tHe metadAta that tELLs you tHaT It wAs packaged on sEpteMbeR 25 2011 at 342pM Utc mAnuFactuRed by LIceNSeD veNdOr numbeR 5 at the peoria Il Usa PLanT IN buIlDIng 2 and WAS ThE 243rD pacKagE off ThE line IN That shIFT and wAs inSpeCtEd by inSpEctor numbEr 45