user82585: In most of the conventional blockchains, blocks are validated instead of transactions. Why cant' transactions validated directly?
The structure of basic blockchains are linked lists, by having DAGs, is it possible to have a graph-chain of transactions?

user15715: Some transactions cannot be fully validated outside of blocks.
If you use OP_CLTV, a transaction can be valid only after a certain block height, and not before ; if you don't know which block it's in, there's no way to know if it is valid or not.

user26481: To be more precise, blocks are timestamped, transactions in a block are validated. Timestamping creates a timeline so that it says B pays C can happen, since A pays B has been timestamped
Its perfectly fine to have one transaction per block if your network is used by you and your few friends. But, this is not scalable to be used by the whole world, since we only get 1block every 10 minutes

82585: <p>In most of the conventional blockchains, blocks are validated instead of transactions. Why cant' transactions validated directly?
The structure of basic blockchains are linked lists, by having DAGs, is it possible to have a graph-chain of transactions?</p>
 15715: <p>Some transactions cannot be fully validated outside of blocks.</p>

<p>If you use <a href="https://github.com/bitcoin/bips/blob/master/bip-0065.mediawiki" rel="nofollow noreferrer">OP_CLTV</a>, a transaction can be valid only after a certain block height, and not before ; if you don't know which block it's in, there's no way to know if it is valid or not.</p>
 26481: <p>To be more precise, blocks are <em>timestamped</em>, transactions in a block are validated. Timestamping creates a timeline so that it says <em>B pays C</em> can happen, since <em>A pays B</em> has been timestamped</p>

<p>Its perfectly fine to have one transaction per block if your network is used by you and your few friends. But, this is not scalable to be used by the whole world, since we only get 1block every 10 minutes</p>
