Terminology

Question

How do terms like "stream" and "stream items" map to blocks and challenges?
What happens (under the hood) when I publish an item on a stream?
- does it get verified?
- can I see who was the first to verify it?
How is integrity maintained? (typically, the hash of an entire block is made and used in the calculation of the hash of a new block)
- is it the same for items in a stream?

Answer 1

A stream item is published in a transaction like any other blockchain transaction, and it gets verified in the usual way, as part of a block of transactions built by a "miner", which then enters a chain in which other "miners" participate. You can think of it as a transaction which is all metadata, and no asset, because under the hood that's what it really is. But from a security perspective it behaves like any other transaction.

Comments

That does not answer all my questions.
How can I (which API command) get the information on which node verified a given stream-item?

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If you pass true for the 'verbose' parameter for any API for retrieving stream items, such as liststreamitems, you will see a 'blockhash' field. This is the identifier of the block in which the item was confirmed. You can then use the getblock API with this hash to get information about that block, including the 'miner' field which gives the address that was used to sign the block. Assuming you're not sharing private keys between nodes, this will also identify the node.