Generalized transaction

The mempool (and, accordingly, blocks) consist of "generalized transactions"; this could be "proper" transactions (transferring funds) but also other kinds of things such as update proposals, delegations, etc.

" Validated " transaction or block

The ledger defines how to validate transactions and blocks. It's possible the type before and after validation may be distinct (eg Alonzo transactions), which originally motivated this family.

We also gain the related benefit that certain interface functions, such as those that reapply blocks, can have a more precise type now. TODO

Similarly, the Node-to-Client mini protocols can explicitly indicate that the client trusts the blocks from the local server, by having the server send Validated blocks to the client. TODO

Note that validation has different implications for a transaction than for a block. In particular, a validated transaction can be " reapplied " to different ledger states, whereas a validated block must only be " reapplied " to the exact same ledger state (eg as part of rebuilding from an on-disk ledger snapshot).

Since the ledger defines validation, see the ledger details for concrete examples of what determines the validity (wrt to a LedgerState) of a transaction and/or block. Example properties include: a transaction's claimed inputs exist and are still unspent, a block carries a sufficient cryptographic signature, etc.