An object is associated with an identifier which is detectable on the object. The identifier may be an inherent characteristic of the object itself or its packaging, or it may reflect a random or arbitrary value which may then be disposed on the object or its packaging deliberately in a readable form for the purposes of the invention. Additionally, there is disposed a machine readable code comprising a URI incorporating a representation of the object identifier encoded according to one of a number of predefined encoding methods (algorithm and associated parameters), and an encoding identifier, specifying the encoding method used. A reader can read the machine readable code, decode it according to specified encoding method, and prepare a representation of it for comparison with the characteristic reflecting the object identifier. The machine readable code and the characteristic reflecting the object identifier may be readable for example by optical, tactile, radio, olfactive or acoustic mechanisms. The URI may additionally be defined to call a local resource adapted to process the code. The URI may additionally be defined to specify a web site.