How will sharding differ from federated sidechains?

Question

I suppose sharding will be implemented in the future, and there will be many mini-islands that hold only parts of the blockchain.

Does it mean that local nodes will mostly support local TX? If I live in Paris for example, then most of the nodes will hold records of the local transactions to speed things up? And what if I want to send money to Buenos Aires for Example? Will I need to find a node that will link me to the main chain and then another node that will store my transaction on the Buenos Aires Shard? Sending my transaction to another Shard will force all the nodes on my current Shard to download and hold the relevant blocks?

I understand it doesn't have to be a _geo-shard and that sharding can also take place between companies or other entities.

And how will it differ from the (proposed) federated sidechains?

Answer 1

Because it's completely integrated into the protocol and all interoperable. Side chains imply that there isn't really a consensus underneath that binds the two, it's sort of hacked together. Shards all operate under the exact same consensus structure.

Answer 2

Also have a look at https://github.com/ethereum/wiki/wiki/Sharding-FAQ#how-does-plasma-state-channels-and-other-layer-2-technologies-fit-into-the-trilemma and https://github.com/ethereum/wiki/wiki/Sharding-FAQ#could-sharded-blockchains-do-a-better-job-of-dealing-with-network-partitions for more information.