Service Combinators

• Formalism to retrieve web pages [Cardelli & Davies 97]

• Examples:

  • Page retrieval primitives:
    • getpage(url)
    • postpage(url, parameters, …)
  • Conditional execution: S ? T
  • Parallel execution: S | T
  • Timeout: timeout(sec, S)
  • Repetition until success: repeat(S)

repeat( (getpage(“http://a”) | getpage(“http://b”))

?

(sleep(60) ; fail)

)

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