Many of the innovative proposals for blockchain technology reach their potential by leveraging what is commonly called a “smart contract”, a programmable contract which can be executed and enforced automatically on a distributed ledger. Using a ledger simply as a record of ownership does not capture the full potential of distributed ledgers; in their most useful incarnation, this software can automate transactions with programmable ownership. A ledger can only achieve sophisticated transaction logic and automation through smart contracts, which can create robust conditions for execution specific to certain actors. 

http://r3cev.com/blog/2016/2/16/the-problem-with-the-problem-with-oracles