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There are many standards, protocols and existing solutions in the area of IoT. There is and most likely will be no single kind of identifier. Identifier (see a There is no special identifier for IoT. And there won't be one kind of Identifier.
mapping and discovery become important services of larger IoT deployments. Let's give an example: A street lamp might have a field bus address consisting of 2 bytes. It is connected with a gateway. Within the gateway the lamp is mapped to "lamp 123". A lamp management system can switch on and off "lamp123". Via a REST interface the lamp management system exposes the lamp for example as oneM2M "application entity". So other management systems can switch the lamp by sending messages to a specific oneM2M URL. In this example a thing (lamp) is identified with different identifiers that are maped to each other.
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