What data is available to Ethereum smart contracts? I'm wondering - what data is available to the Ethereum smart contracts? I stumbled upon some tutorials on how to write the contracts that give some indication as to a few examples of the data is available, but a more comprehensive list / wiki page would be useful to have for reference.
I'm not sure if this is actually complete, but the solidity language runtime exposes most of the useful stuff:

https://github.com/ethereum/wiki/wiki/Solidity-Tutorial#block-and-transaction-properties

So basically, only existing state and new data entered as arguments from new signed transactions. This means "real world" data mostly has to come from some kind of oracle mechanism.