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< bigwig > A Programming Language for Developing Interactive Web Services

< bigwig > A Programming Language for Developing Interactive Web Services. Claus Brabrand. BRICS , University of Aarhus, Denmark. Plan. Introduction Runtime Model Dynamic Documents PowerForms Conclusion. Plan. Introduction Runtime Model Dynamic Documents PowerForms Conclusion.

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< bigwig > A Programming Language for Developing Interactive Web Services

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  1. <bigwig>A Programming Languagefor DevelopingInteractive Web Services Claus Brabrand BRICS, University of Aarhus, Denmark Microsoft Research <bigwig> March 20, 2000

  2. Plan • Introduction • Runtime Model • Dynamic Documents • PowerForms • Conclusion Microsoft Research <bigwig> March 20, 2000

  3. Plan • Introduction • Runtime Model • Dynamic Documents • PowerForms • Conclusion Microsoft Research <bigwig> March 20, 2000

  4. What is <bigwig>? • A domain-specific high-level programming language for developing interactive Web services. HTML JavaScript Service Specification <bigwig> CGI Scripts HTTP Auth. Java Applets Microsoft Research <bigwig> March 20, 2000

  5. A collection of DSLs • C-like skeleton language with • Runtime system • Concurrency control • Database • Dynamic documents: DynDoc • Input validation language: PowerForms • Security • Cryptographic security • Syntactic-level macros Microsoft Research <bigwig> March 20, 2000

  6. A collection of DSLs • C-like skeleton language with • Runtime system (briefly) • Concurrency control (briefly) • Database • Dynamic documents: DynDoc • Input validation language: PowerForms • Security • Cryptographic security • Syntactic-level macros Microsoft Research <bigwig> March 20, 2000

  7. DSL vs. GPL • DSL ::= Domain Specific Language • GPL ::= General Purpose Language • DSL? • Targeted for specific problem domain • Abstraction level match problem domain • Examples: Lex/Yacc, LaTeX Microsoft Research <bigwig> March 20, 2000

  8. DSL vs. GPL • DSL ::= Domain Specific Language • GPL ::= General Purpose Language • DSL? • Targeted for specific problem domain • Abstraction level match problem domain • Examples: Lex/Yacc, LaTeX, <bigwig> Microsoft Research <bigwig> March 20, 2000

  9. DSL Advantages(vs. GPL + library) • Syntax • Design (and restrict) expressibility • Syntax conveys nature of constructs • Analysis • Analyze domain specific aspects • Implementation • Efficient implementation • Rely on syntax restrictions and analysis information Microsoft Research <bigwig> March 20, 2000

  10. Goals • Lower development time (= cost): • Targeted at Web services • Low-level  high-level • Increase functionality: • Compiler does “the dirty work” • Increase reliability: • Catch errors during development • Runtime errors  Compile-time errors Microsoft Research <bigwig> March 20, 2000

  11. Assumptions • “Rules of engagement”: • Lowest common denominator • Any browser/Web server combination • Only include basic primitives • Syntactic macro language does the rest Microsoft Research <bigwig> March 20, 2000

  12. Target Audience • Programmers! • No expert Web knowledge required • No multiple choice questionnaires “Reduce Web service development to a standard programming task.” Microsoft Research <bigwig> March 20, 2000

  13. Core Language Features • C-like to minimize syntactic burdens • Not C-like features: • Garbage collection • Relations, vectors, tuples • Strong type checking Microsoft Research <bigwig> March 20, 2000

  14. People • 1x Michael I. Schwartzbach • 1x Post Doc. • 5x Ph.D. students • 2x Programmers • 2x Testers • 1x External contributor Microsoft Research <bigwig> March 20, 2000

  15. Plan • Introduction • Runtime Model • Dynamic Documents • PowerForms • Conclusion Microsoft Research <bigwig> March 20, 2000

  16. Plan • Introduction • Runtime Model • Dynamic Documents • PowerForms • Conclusion Microsoft Research <bigwig> March 20, 2000

  17. 3 Approaches Script-centered Perl/CGI Microsoft Research <bigwig> March 20, 2000

  18. 3 Approaches ASP, PHP Page-centered Script-centered Perl/CGI Microsoft Research <bigwig> March 20, 2000

  19. 3 Approaches Mawl, <bigwig> Session-centered ASP, PHP Page-centered Script-centered Perl/CGI Microsoft Research <bigwig> March 20, 2000

  20. Script-Centered A script A script A page A page A script A page Microsoft Research <bigwig> March 20, 2000

  21. Page-Centered A page A page A page Microsoft Research <bigwig> March 20, 2000

  22. Page-Centered “Service code embedded in tags and interpreted by specialized Web server” • Increased level of abstraction • Easy to add dynamics to static pages • Scalability Microsoft Research <bigwig> March 20, 2000

  23. Script- vs. Page-Centered • As the service complexity increases: • Page-centered  Script-centered • Script-centered: • default programming, escape printing. • Page-centered: • default printing, escape programming. Microsoft Research <bigwig> March 20, 2000

  24. (Fundamental) Problems • Interpretation-based: • Typically no static checks • (Efficiency) • Not domain specific: • Cannot check Web related issues • Implicit control-flow: • A service = A collection of scripts/pages! Microsoft Research <bigwig> March 20, 2000

  25. Language Requirements • Compilation-based: • Static checks • (Efficiency) • Domain specific: • Check Web related issues • Explicit control-flow: • A clear service specification Microsoft Research <bigwig> March 20, 2000

  26. Language Requirements • Compilation-based: • Static checks • (Efficiency) • Domain specific: • Check Web related issues • Explicit control-flow: • A clear service specification Microsoft Research <bigwig> March 20, 2000

  27. Session-Centered client: server: e show show e one service program Internet Microsoft Research <bigwig> March 20, 2000

  28. Hello World service { session Hello() { html D = <html>Hello World!</html>; show D; } } Microsoft Research <bigwig> March 20, 2000

  29. Hello World service { session Hello() { show <html>Hello World!</html>; } } Microsoft Research <bigwig> March 20, 2000

  30. A Page Counter service { session Access() { sharedint counter; string name; show EnterName receive [name=name]; counter = counter + 1; show AccessDoc <[counter = counter]; } } Microsoft Research <bigwig> March 20, 2000

  31. A Page Counter  if (counter == 100) { counter = 0; show Congratulations <[name = name]; } else { counter = counter + 1; show AccessDoc <[counter = counter]; }  Microsoft Research <bigwig> March 20, 2000

  32. CGI Shortcomings • Stateless protocol • Session model requires state • No bookmarking • CGI URL bookmarked, not HTML URL • Back-button problem • “Step-back-in-time” does not make sense • Long response times • Clients get impatient Microsoft Research <bigwig> March 20, 2000

  33. Our Solution • Runtime System (based on CGI) • “Any browser/Web server combination” • Problems: Solutions: • Stateless protocol • No bookmarking • Back-button problem • Long response times Microsoft Research <bigwig> March 20, 2000

  34. Our Solution • Runtime System (based on CGI) • “Any browser/Web server combination” • Problems: Solutions: • Stateless protocol connector process • No bookmarking • Back-button problem • Long response times Microsoft Research <bigwig> March 20, 2000

  35. Our Solution • Runtime System (based on CGI) • “Any browser/Web server combination” • Problems: Solutions: • Stateless protocol connector process • No bookmarking use html reply file • Back-button problem • Long response times Microsoft Research <bigwig> March 20, 2000

  36. Our Solution • Runtime System (based on CGI) • “Any browser/Web server combination” • Problems: Solutions: • Stateless protocol connector process • No bookmarking use html reply file • Back-button problem use html reply file • Long response times Microsoft Research <bigwig> March 20, 2000

  37. Our Solution • Runtime System (based on CGI) • “Any browser/Web server combination” • Problems: Solutions: • Stateless protocol connector process • No bookmarking use html reply file • Back-button problem use html reply file • Long response times + refresh + timeout Microsoft Research <bigwig> March 20, 2000

  38. Runtime System • Availability: • in <bigwig> compiler • as stand-alone package • Underway... • Specialized runtime system: • CGI  Specialized Web server • efficiency, scalability Microsoft Research <bigwig> March 20, 2000

  39. Concurrency Control • Problem: • Parallel service processes. • Access shared resources. • Require synchronization. • Example: counter = counter + 1; Microsoft Research <bigwig> March 20, 2000

  40. Counter Example  counter = counter + 1;  Microsoft Research <bigwig> March 20, 2000

  41. Counter Example …add checkpoints  waitA; counter = counter + 1; waitB;  Microsoft Research <bigwig> March 20, 2000

  42. Counter Example …and constraints (“M2L-Str” logic) t,t’’: A(t)  A(t’’)  t<t’’  t’: t<t’<t’’  B(t’)  waitA; counter = counter + 1; waitB;  Microsoft Research <bigwig> March 20, 2000

  43. Counter Example “Ensure that service obeys constraints” t,t’’: A(t)  A(t’’)  t<t’’  t’: t<t’<t’’  B(t’)  waitA; counter = counter + 1; waitB;  Exclusive access Microsoft Research <bigwig> March 20, 2000

  44. Compilation Process t,t’’: A(t)  A(t’’)  t<t’’  t’: t<t’<t’’  B(t’) Mona DFA: Microsoft Research <bigwig> March 20, 2000

  45. In practice... service { session Access() { sharedint counter;  counter = counter + 1;  } } Microsoft Research <bigwig> March 20, 2000

  46. Syntax Macros service { session Access() { regionsharedint counter;  exclusive (counter) { counter = counter + 1; } } } Microsoft Research <bigwig> March 20, 2000

  47. Demo Example: Mutex labelA, B; t,t’’: A(t)  A(t’’)  t<t’’  t’: t<t’<t’’  B(t’) Microsoft Research <bigwig> March 20, 2000

  48. Demo Example: Mutex labelA, B; t,t’’: A(t)  A(t’’)  t<t’’  t’: t<t’<t’’  B(t’) session A() { while (!quit) { waitA; show Passed_A; } } Microsoft Research <bigwig> March 20, 2000

  49. Demo Example: Mutex labelA, B; t,t’’: A(t)  A(t’’)  t<t’’  t’: t<t’<t’’  B(t’) session A() { while (!quit) { waitA; show Passed_A; } } session B() { while (!quit) { waitB; show Passed_B; } } Microsoft Research <bigwig> March 20, 2000

  50. Plan • Introduction • Runtime Model • Dynamic Documents • PowerForms • Conclusion Microsoft Research <bigwig> March 20, 2000

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