When harmonizing devices communicating using different technologies, the question of complexity arises. If you have only two technologies, only one bridge is required. If you need to bridge three technologies, three bridges would be required. But how about four technologies? Do you need to create six bridges? Or 10 bridges between five technologies? 15 bridges for six technologies? For N technologies, you would need N(N - 1) / 2 bridges, at least if you bridge them directly between each other, as is shown in the following image. This process has an order of complexity of N2, which is clearly not maintainable as technologies grow. If somebody introduces a new technology, either that party needs to create bridges to every other technology that exists, or each technology provider needs to create a bridge to the new technology:

A more fruitful method is to create an abstraction layer that can act as an intermediary between each technology. In such a case, the complexity of the system would be linear. Any technology provider would only have to provide a bridge to that abstraction layer, to be able to participate in the harmonized network, as is shown in the following image: