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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 System Dynamic Documents PowerForms Conclusion. Plan. Introduction Runtime System 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 Datalogforeningen <bigwig> December 7, 1999

  2. Plan • Introduction • Runtime System • Dynamic Documents • PowerForms • Conclusion Datalogforeningen <bigwig> December 7, 1999

  3. Plan • Introduction • Runtime System • Dynamic Documents • PowerForms • Conclusion Datalogforeningen <bigwig> December 7, 1999

  4. What is <bigwig>? • A domain-specific high-level programming language for developing interactive Web services. HTML JavaScript Service Specification <bigwig> CGI HTTP Auth. Java Applets Datalogforeningen <bigwig> December 7, 1999

  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 Datalogforeningen <bigwig> December 7, 1999

  6. 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 Datalogforeningen <bigwig> December 7, 1999

  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 Datalogforeningen <bigwig> December 7, 1999

  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> Datalogforeningen <bigwig> December 7, 1999

  9. DSL Advantages …vs. GPL + library • Syntax • Analysis • Implementation Datalogforeningen <bigwig> December 7, 1999

  10. Goals • Lower development time (= cost): • Targeted at Web services • Low-level  high-level • Increase functionality: • Compiler does “the dirty work” • Reliability: • Catch errors during development • Runtime errors  Compile-time errors Datalogforeningen <bigwig> December 7, 1999

  11. Assumptions • “Rules of engagement”: • Lowest common denominator • Any browser/Web server combination • Only include basic primitives • Syntactic macro language does the rest Datalogforeningen <bigwig> December 7, 1999

  12. Target Audience • Programmers! • No expert Web knowledge required • No multiple choice questionnaires or drag’n’drop “Reduce Web service development to a standard programming task.” Datalogforeningen <bigwig> December 7, 1999

  13. Core Language Features • C-like to minimize syntactic burdens • Features: • Garbage collection • Relations, vectors, tuples • Strong type checking Datalogforeningen <bigwig> December 7, 1999

  14. People • 1x Michael I. Schwartzbach • 1x Post Doc. • 3x Ph.D. students • 2x Programmers • 2x Testers • 1x External contributor Datalogforeningen <bigwig> December 7, 1999

  15. Plan • Introduction • Runtime System • Dynamic Documents • PowerForms • Conclusion Datalogforeningen <bigwig> December 7, 1999

  16. Plan • Introduction • Runtime System • Dynamic Documents • PowerForms • Conclusion Datalogforeningen <bigwig> December 7, 1999

  17. 3 Approaches Script-centered Perl/CGI Datalogforeningen <bigwig> December 7, 1999

  18. 3 Approaches Script-centered Perl/CGI ASP, PHP Page-centered Datalogforeningen <bigwig> December 7, 1999

  19. 3 Approaches Script-centered Perl/CGI ASP, PHP Page-centered Mawl, <bigwig> Session-centered Datalogforeningen <bigwig> December 7, 1999

  20. Script-Centered A script A script A page A page A script A page Datalogforeningen <bigwig> December 7, 1999

  21. Page-Centered A page A page A page Datalogforeningen <bigwig> December 7, 1999

  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 Datalogforeningen <bigwig> December 7, 1999

  23. Script / Page-Centered • As the service complexity increases: • Page-centered  Script-centered • Script-centered: • default programming, escape printing. • Page-centered: • default printing, escape programming. Datalogforeningen <bigwig> December 7, 1999

  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! Datalogforeningen <bigwig> December 7, 1999

  25. Language Requirements • Compilation-based: • Static checks • (Efficiency) • Domain specific: • Check Web related issues • Explicit control-flow: • A clear service specification Datalogforeningen <bigwig> December 7, 1999

  26. Session-Centered client: server: N show show N Internet Datalogforeningen <bigwig> December 7, 1999

  27. Hello World service { session Hello() { html D = <html>Hello World!</html>; show D; } } Datalogforeningen <bigwig> December 7, 1999

  28. Hello World service { session Hello() { show <html>Hello World!</html>; } } Datalogforeningen <bigwig> December 7, 1999

  29. A Page Counter service { session Access() { globalint counter; string name; show EnterName receive [name=name]; counter = counter + 1; show AccessDoc <[counter = counter]; } } Datalogforeningen <bigwig> December 7, 1999

  30. A Page Counter  if (counter == 100) { show Congratulations <[name = name]; counter = 0; } else { show EnterName receive [name=name]; }  Datalogforeningen <bigwig> December 7, 1999

  31. CGI Shortcomings • Stateless protocol • Session model requires state • No bookmarking • CGI, not HTML URL • Back-button problem • “Step-back-in-time” does not make sense Datalogforeningen <bigwig> December 7, 1999

  32. CGI Shortcomings • Stateless protocol • No bookmarking • Back-button problem Datalogforeningen <bigwig> December 7, 1999

  33. CGI Shortcomings • Stateless protocol • No bookmarking • Back-button problem Datalogforeningen <bigwig> December 7, 1999

  34. Components client CGI HTML Internet HTTP server CGI HTML restore ; compute ; save program database Datalogforeningen <bigwig> December 7, 1999

  35. Adding a ”Connector” client CGI HTML Internet HTTP server CGI HTML redirect connector CGI HTML restore ; compute ; save program database Datalogforeningen <bigwig> December 7, 1999

  36. CGI Shortcomings • Stateless protocol • No bookmarking • Back-button problem Datalogforeningen <bigwig> December 7, 1999

  37. CGI Shortcomings • Stateless protocol • No bookmarking • Back-button problem Datalogforeningen <bigwig> December 7, 1999

  38. Components client CGI HTML Internet HTTP server CGI HTML connector CGI HTML program database Datalogforeningen <bigwig> December 7, 1999

  39. Adding an HTML “Reply File” client CGI jump Internet HTTP server CGI jump connector CGI done! HTML reply file program HTML database Datalogforeningen <bigwig> December 7, 1999

  40. CGI Shortcomings • Stateless protocol • No bookmarking • Back-button problem Datalogforeningen <bigwig> December 7, 1999

  41. CGI Shortcomings • Stateless protocol • No bookmarking • Back-button problem Datalogforeningen <bigwig> December 7, 1999

  42. Components client CGI jump Internet HTTP server CGI jump connector CGI done! HTML reply file program HTML database Datalogforeningen <bigwig> December 7, 1999

  43. Components client CGI jump Internet HTTP server CGI jump connector same URL CGI done! HTML reply file program HTML database Datalogforeningen <bigwig> December 7, 1999

  44. CGI Shortcomings • Stateless protocol • No bookmarking • Back-button problem Datalogforeningen <bigwig> December 7, 1999

  45. Additional Problems Datalogforeningen <bigwig> December 7, 1999

  46. Additional Problems Datalogforeningen <bigwig> December 7, 1999

  47. What is going on? • Error? • Package Lost, Service Crash, Connection down? • Ok? • Searching Database, Long Computation, Waiting for a Resource? • Would like to explain delays: • “searching database, please wait...” Datalogforeningen <bigwig> December 7, 1999

  48. Components client CGI jump Internet HTTP server CGI jump connector CGI done! HTML reply file program HTML database Datalogforeningen <bigwig> December 7, 1999

  49. Adding a Connector Timeout client CGI jump Internet HTTP server CGI jump connector Timeout CGI done HTML reply file program update database Datalogforeningen <bigwig> December 7, 1999

  50. Concurrency Control • Problem: Parallel service processes. • Access shared resources. • Require synchronization. • Solution: • Specification of checkpoints & constraints • Synthesize centralized safety controller • Ensures that service obeys constraints. Datalogforeningen <bigwig> December 7, 1999

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