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Point 2: Hide Everything From the User
Except Functions

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• The user does not care about the formal semantics...or even concurrency!
• The user just wants to run some Web Services!
• What level of abstraction should the user focus on Web Services on?
• The answer is just the functions: as in functional programming.
• Which are easily formalized in the λ calculus.
• The user invokes a function and the Web does all the composition until the function is received.
• Example of "Safe Withdrawal": Check money is in an account before withdrawal - decomposes into checking balance after transaction, if true that balance is above zero, then commit transaction.