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The Jakarta Tool Suite

The Jakarta Tool Suite. Don Batory Department of Computer Sciences University of Texas at Austin . Introduction. Central problems in Software Engineering stem from one fact: Complaints about the lack of: quality, performance, reliability, maintainability, evolvability.

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The Jakarta Tool Suite

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  1. The Jakarta Tool Suite Don Batory Department of Computer Sciences University of Texas at Austin

  2. Introduction • Central problems in Software Engineering stem from one fact: • Complaints about the lack of: • quality, performance, reliability, maintainability, evolvability software is written by hand

  3. Quality of Software • Function of: • basic design • “build it several times to get it right” • designs improved with experience • programming staff • How can we do better? • to exploit previous experiences? • to improve quality of programmers?

  4. Future of Software Engineering • Automated production of rote software • major improvements in: performance, reliability, quality… • Domain-specific component technologies • engineering approach that standardizes: • designs (programming problems) • implementations (programming solutions)

  5. Generators • Generators are tools that: • transform component compositions into code • validate compositions automatically • automatic customizations and optimizations • Software quality improved • use good designs, expert programmers • expect good performance & reliability, easier maintenance, extensibility

  6. What are Generators? • Generators are compilers for: • domain-specific languages • general-purpose programming languages with domain-specific extensions • Problem: • generators are hard to build • programming infrastructure is lacking • 60% of effort focuses on infrastructure

  7. The Jakarta Tool Suite (JTS) • for building component technologies and generators in Java • based on experiences in building multiple generators • compiler tools (POPART, Dialect, TXL), MS’s IP • for language extensibility • creates preprocessors for domain-specific languages (DSLs) or embedded DSLs • for architectural optimizations needed for self-adaptive software

  8. Language Extensibility isn’t new... • LISP macros & CLOS meta-object protocols • Language extensibility of JTS based on different packaging architectural extensibility • same techniques used in avionics, network protocols, database systems were applied to programming languages • unit of extensibility is a “layer” or “building block” of a family of programming languages

  9. This Presentation... • Jak Language • open, extensible version of Java • its basic features • Bali Generator • of customized dialects of Jak • (product-line of dialects of Java) • Adaptive Software • demo • Status Report and Conclusions

  10. The Jak Language open, extensible superset of Java examine “base” extension

  11. Support for Metaprogramming • Extends Java with: • AST constructors • represent and manipulate programs as data • adds LISP quote/unquote to Java • AST traversals, manipulation • arbitrary program transformations • Generation scoping • variant of hygienic macros

  12. AST Constructors • Added constructors for code fragments of different types (expression, statement, …) • similar to LISP quote AST_Exp e = exp{ 7 + x*8 }exp; AST_Stm s = stm{ if (y>4) return r; }stm; e.unparse( ); // outputs “7 + x*8” s.unparse( ); // outputs “if (y>4) return r;”

  13. Parameterization and Composition of Code Fragments • Explicit escapes • LISP unquote AST_Exp e = exp{ 7 + x*8 }exp; AST_Exp s = stm{ if (($exp(e))>4) return r; }stm; s.unparse( ): // outputs: “ if ((7+x*8)>4) return r; ”

  14. AST Constructors (Continued) • Focusing on AST constructors for Java (or extended Java) • Add AST constructors for other languages • CORBA IDL • Embedded SQL • (subsets of) C, C++ • ...

  15. int temp = 5; macro(temp); Application Code int temp = 5; { int temp = 2*temp; … } int temp = 5; { int temp = 2*temp; … } Bogus Generated Code Hygienic, lexically scoped macros (HLSM) The Binding Problem macro(x) { int temp = 2*x; … } Macro Definition

  16. Generation Scoping • Generalization of HLSM for generators • Y. Smaragdakis added to Microsoft’s IP • validated with DiSTiL • convenient solution to “binding problem” • Different than HLSM • generators are not reflective, macro-based • GS allows you to maintain the name-space of the generated program • generator language different than generated language

  17. AST Traversals • Package/classes for depth-first searches, manipulations • support arbitrary program transformations AstCursor c = new AstCursor( ); Ast_Node root = // root of AST to search for (c.First(root); c.More( ); c.PlusPlus( ) ) if (c.node instanceof AstInterface) c.Delete( );

  18. How Jak Works

  19. SSTs versus ASTs • Surface syntax tree (SST) is a syntactically correct parse tree • tree constructors, modifiers guarantee syntactic correctness • SSTs may not be semantically correct • Abstract syntax tree (AST) is a type-checked SST • with annotations to symbol table • invoked by typecheck( ) method to root of SST

  20. Extensibility of SST/ASTs • “Intentions” • add AST nodes with domain-specific semantics • P3 adds cursor, container types to Java • at reduction time, intention nodes are replaced with their Java (or host language) implementations • P3 replaces cursor, container AST nodes with their concrete Java implementations

  21. domain specific program Written in Jak lexer and parser AST transform program Java program Jak Jakarta Follows DSL Paradigm

  22. Parser creates SST of a domain-specific program Jak type checks SST to convert to AST Jak replaces intentions with SSTs If necessary, SSTs can be type checked to form ASTs intentions More Detail: Processing in Phases

  23. Big Picture • JTS/Jak is technology marriage of: • Java • metaprogramming concepts • quote, unquote, generation scoping (HLSM) • intention-based programming andtransformation systems • Inherently “open” compiler

  24. How to... • Produce lexers and parsers? • Produce transform program? • Where does GenVoca fit in?answers in remainder of talk...

  25. Bali GenVoca Generator of Precompilers of Java Dialects

  26. Family Languages • Jak is a family of related languages • versions with/without constructors • with/without P3 extensions • with/without CORBA IDL extensions… • Classic library scalability problem • n optional, largely orthogonal features • 2n different possible combinations of features • cannot build all 2n combinations by hand • can generate them

  27. Bali is a GenVoca Generator • Bali assembles variants of Jak from components • Components encapsulate primitive extensions • generation scoping • domain-specific generators like P3 • CORBA IDL • … • Compositions of components specifies particular variant

  28. Two Aspects • Tool for writing compilers for Domain-Specific Languages(DSL) • looks similar to other DSL-compiler tools • specify syntax of DSL or language extension • annotated, extended BNF grammars • GenVoca generator • software component technology • architectural, extensibility aspects

  29. Domain-Specific Language Compiler Tool

  30. Bali Grammars • Extended BNF grammar • extended to handle repetitions • e.g., POPART StatementList : ( Statement )+ ; ArgumentList : Argument ( ‘,’ Argument )* ;

  31. constructors: IfStm( token, token, ASTexp, token, ASTstm ) SwitchStm( token, token, ASTexp, token, ASTblk ) Bali Grammars • Annotated • by class to instantiate when production is recognized • POPART, DIALECT, common OO design techniques SelectionStmt : IF ‘(’ Expr ‘)’ Statement :: IfStm | SWITCH ‘(’ Expr ‘)’ Block :: SwitchStm ;

  32. Rule1 C1 Rule2 C2 C3 Inheritance Hierarchies • is deduced from DSL grammar Rule1 : pattern1 :: C1 | Rule2 ; Rule2 : pattern2 :: C2 | pattern3 :: C3 ;

  33. Bali Specifications • Jak grammar • 170 tokens • 400 productions • 800 lines • Bali grammar • 15 tokens • 20 productions • 73 lines // bali spec lexical patterns %% grammar rules

  34. What can be generated... • Lexical analyzer • Jlex (java version of lex) • Bernie Lofaso (Jakarta Team Member) • Parser • Java_Cup (java version of yacc) • Scott Hudson@Georgia Tech • Inheritance hierarchy and AST classes • constructors, unparsing, editing methods Now moving to JavaCC

  35. AstNode JTS kernel class Bali-generated classes IfStm’ SwitchStm’ … IfStm SwitchStm Hand-coded subclasses … What can’t be generated... • Type checking, reduction, optimization methods • AST node specific • hand code as subclasses to Bali-generated class

  36. Big Picture • Traditional approach to building compilers for domain-specific languages • clean model of proven technology • Problem: don’t want to hand-code and hand-assemble each variant • too expensive • Solution: GenVoca component technology • components encapsulate primitive extensions • compose components to form variants of Jak

  37. GenVoca Generators

  38. GenVoca • Model of parameterized programming • addresses the architectural aspects of software • building blocks of domains are refinements of fundamental domain abstractions • components are implementations of refinements • components composed by parameter instantiation • visualize component composition as stacking layers

  39. X Z[ ] Y [ ] Z Y X Quick Tutorial • Components define algebraic operators • Software system is typeequation System: System = Question: what is relationship of components to classes?

  40. class subclassing relationship subclass OO Realizations of Refinements • A small-scale refinement adds new data members, methods, and/or overrides existing methods to a class

  41. class class class subclass subclass subclass Large Scale Refinement • Adds new data members and methods simultaneously to several classes

  42. application classes Relationship to GenVoca • GenVoca components are large scale • consistent refinements of multiple classes

  43. Guard With Java Kernel Application Classes Relationship to JTS AstNode

  44. Guard With Java Kernel To Scale, Not to Scale... AstNode >500 classes J1 = Guard[ With[ Java[ Kernel ] ] ];

  45. Component x y z w Express Components as Mixin Layers • Mixins are classes whose superclass is specified via a parameter • Components are expressed as a mixin (whose superclass is the “lower layer”) • inner classes themselves are mixins

  46. Guard With Java Kernel Mixin-Layer Construction Elegant model of component-based software construction

  47. Big Picture • Bali is marriage of: • DSL compiler technology • GenVoca generator technology • Bali synthesizes versions of Jak thru component composition • automatic synthesis of lexer, parser, transform engine • can synthesize variants of other languages, too

  48. Current Status and Future Work

  49. Compose Component Definition and Composition LayerDef Macros Embedded DSL GenVoca Generator for Containers P3 SymTab Match Metaprogramming AST Constructors Hygienic Macros GScope AST Java1.1 Base Language Java1.0 Current JTS Language Legend 1998 1997

  50. Current Status • Jakarta now supports: • AST constructors and escapes • generation scoping • parameterized inheritance (mixin layers) • P3 generator of container data structures • Add type checking to AST nodes • needed for semantics-based transformations • FSATS • Fire Support Automated Test System

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