Sustainable digitization of factories (and especially IoT) requires all data related to “things” (products, equipment, but also informational objects) to be stored for later reference in a so-called digital shadow. This paper addresses an identity question: “which data should be stored as a so-called digital shadow of an object?” and identifies two opposing principles, Single Source of the Truth vs Local Autonomy. The first principle keeps data objects small and uses links to other data objects. It expands object’s life time. The second principle advices to keep objects large, reduces linkages but limits object’s life time. The paper analyses these two principles for physical objects as well as for related informational objects. Some guidelines for application are given.