Does the CONOP definition exclude pruning branches from its node definition?

Question

Paul Sztorc in his post Measuring Decentralization defined CONOP as

For this section, the cost of the option to create a full node will be referred to as the “cost of node-option” or “CONOP”.

The implication is that the more full nodes that are being run in a decentralized manner the better.

Monero controls the growth of its blockchain (and thereby the cost to run a node) with an adaptive blocksize that scales based on demand. Riccardo Spagni elaborated on this during his Dynamic Block Size Cap presentation

We know that it is possible to prune Monero (because it is being done already in a Monero fork called Aeon) and that pruning may further reduce the cost of running a node. However, do pruning branches fail to meet the node definition of CONOP as defined by Paul Sztorc? How can Monero balance the security advantages of a network with primarily full nodes with the possibility than pruning might decrease the cost to run a node and lead to more usage?

Answer 1

By definition pruning branches cannot be considered full nodes because they are missing the data that has been pruned. Pruning branches are not full nodes according to the definition of CONOP.

This explanation explains why full nodes (in addition to pruning branches) are necessary.

Pruning data makes a node unable to supply the pruned data to other syncing nodes. That data is necessary to fully validate the blockchain in a trustless manner, so while a client may decide to trust a pruned node, there should be at least a few "full data" nodes on the network, keeping the entirety of the blockchain, in order to keep the ability to re-verify the whole thing from scratch.