[...] altcoins are interesting for research, but not in foreseeable practice - what I am saying get *something* useable in bitcoin, get people hooked, once scalability issues inevitably show up, transition to altchain.
This ignores the benefits of monetary diversity. Bitcoin might be here to stay, but in the future altchains will be most commonly used as they can be tailored to specific environments, and thus provide the most benefit to a community.
Diversity applies between equal players, otherwise it's just treehugger underdog-loving bullshit. Capitalism hates diversity if there is no (obvious, short term) profit in it. Thats what humans are. Technically, you need something to sustain the volume for things to work.
Really? Because that's what Marketcoin is trying to do, and it's not that simple. Maybe if you have two altchains designed to work together... but I'm not aware of a way to do that yet. Care to provide an example?
In bitcoin chain, you create the transaction as usual, but keep it secret until counterparty shows you it's altchain transaction. You send only it's hash (txid) to counterparty on altchain for that purpose. There, transaction has special input opcode 'bitcointxid'. This opcode evaluates to true *only* if the txid is seen actually included in bitcoin blockchain. Naturally, altchain client needs to consult bitcoin blockchain during validation as well (but you need bitcoin anyway for other reasons, even SPV will suffice if you replace txid with hash(txid)). Thus, both transactions become valid only if both parties transmit them on network.
(taken from
https://github.com/bitcoinx/colored-coin-tools/wiki/crosschain-p2ptrade )
Equivalent scheme can be used for OT as well (smart contract which needs bitcoin oracle).