I'd like to know what are some specific actual real world use cases

Visit "Implementing first Industry 4.0 Use Cases with IOTA DAG Tangle — Machine Tagging for Digital Twins" to read about an actual use case by Innogy SE (energy company based in Germany, a subsidiary of the German energy company RWE).

To quote briefly from the article:

In this blogpost my preferred industry 4.0 use case will be described as a first example where the IOTA protocol can be applied in practice today: IOTA for tagging of physical machines in a digital twin architecture (proof-of-concept). This use case combines some very important decentral technologies such as IPFS, IPLD and BigchainDB for file storage and database layer with the DAG (directed acyclic graph) tangle as well.

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