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There are many standards, protocols and solutions in the area of IoT. There is and most likely will be no single kind of identifier. 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.
Policy controled mapping
The mapping process consists of different steps. In every step can be controlled by access policies. This way its possible to control whether an identifier is visible or not or who can "see" a certain thing or not. In our example the policy check could be implemented in the lamp management system or with the REST API.
Mapping and discovery mechanisms and DNS
In most cases DNS (Domain Name Service) can't be used directly. DNS was designed to map between IP-addresses and human readable domain names. DNS is not able to handle identifier from various IoT protocols. It is also not possible to propagate changes in a very short time.But DNS has a outstanding governance process that ensures unique identifiers. So DNS is at least part of most mapping processes. In our example DNS might be used to find the company domain of the lamp management or the address of the REST API.
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