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Research Directions Towards Software Maintenance, Adaptation and Modernization

Research Directions Towards Software Maintenance, Adaptation and Modernization. Suman Roychoudhury. Grammar-based Software Technology - Spring 2006 Programming Lang. Seminar. Maintaining Legacy Code – Tool Support ?. Legacy. 200 Billion Lines of Cobol Source. Commercial + Scientific

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Research Directions Towards Software Maintenance, Adaptation and Modernization

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  1. Research Directions Towards Software Maintenance, Adaptation and Modernization Suman Roychoudhury Grammar-based Software Technology - Spring 2006 Programming Lang. Seminar

  2. Maintaining Legacy Code – Tool Support ? Legacy 200 Billion Lines of Cobol Source Commercial + Scientific Applications Cobol Fortran Object Pascal Software Migration is not an easy task ! Infrastructure, money effort already spent

  3. Current Techniques and Tools • OMG MDA - Model Driven Architecture • OMG KDM - Knowledge Discovery Metamodel • Aspect-Oriented Software Development • Software Refactoring/Mining/Migration • Eclipse IDE/ AspectJ

  4. Aspect Weavers: Current Limitations Several tools and language extensions have been developed to enable aspect weaving :- However – • Specific to a few popular languages (e.g., Java) • New tools are developed from scratch without preserving knowledge of previous construction • No emphasis on re-usability in a different language and platform context

  5. Research Questions • Is there a technique to construct aspect weavers for legacy languages without extending or inventing a new parser (or compiler) from scratch? • Can such construction be supported in a more generic or language-parametric (independent) way? • Can the knowledge of building a weaver from a previous construction be reused in a different language and platform context?

  6. Challenges in Language-Parametric Legacy Adoption Challenge C1 – The Parser Construction Problem Challenge C2 – Type Analysis Problem Challenge C3 – The Code Transformation Problem Challenge C4 – Language-Parametric Generalization of Transformation Objectives Challenge C5 – Accidental Complexities of Transformation Specifications

  7. Transformation System Parser Concrete Syntax Legacy System User Inputs Aspect Language Challenge C1 – The Parser Construction Problem • Scalabilty • Extensibility • Availabilty of AST Framework • Reusabilty Intermediate Syntax Intermediate Type Analysis • C++ • Object Pascal • Fortan • Cobol • Ada • Jovial • VHDL

  8. Transformation System Parser Concrete Syntax Legacy System User Inputs Aspect Language Challenge C2 – Type Analysis Problem • Interaction of aspects with Type System (e.g. computing sub-types for a given type) Intermediate Syntax Intermediate Type Analysis

  9. Transformation System Parser Concrete Syntax Legacy System User Inputs Aspect Language Challenge C3 – The Code Transformation Problem Intermediate Syntax pattern probe_id_pattern1() : unqualified_id = " printf ". rule insert_probe1 (s: statement_seq): function_body -> function_body = " { \s } " -> "{ \probe_id_pattern1\(\) (\"Entering Method…\"); { \s } }". Intermediate Type Analysis

  10. Transformation System Parser Concrete Syntax Legacy System User Inputs Aspect Language Challenge C4 – Language-Parametric Generalization of Transformation Objectives Intermediate Syntax pattern probe_id_pattern1() : IUnqualifiedId = "IFunctionName". rule insert_generic_probe1 (s: IStatementList): IFunctionDecl -> IFunctionDecl = " \Block_Begin \s \Block_End" -> "\Block_Begin \probe_id_pattern1\(\) (\"Entering Method…\"); \Block_Begin\s \Block_End \Block_End". Intermediate Type Analysis

  11. Transformation System Parser Concrete Syntax Legacy System User Inputs AspectLanguage Challenge C5 – Accidental Complexities of Transformation Specifications Intermediate Syntax • A high level aspect language • layered on top of the base system • Translates to low level specifications Intermediate Type Analysis aspectinsert_probe1 { before(): execution (function_declaration) { // insert print statement } }

  12. Goal Statement Goal 2 : Re-use core transformations across language domains usinglanguage parametric transforms (C2, C4) Goal 1 : Raise the level of abstraction (aspect layering) for end-programmers (C5) Program Transformation System (C1,C3) Parametric Transforms Low Level xForm constructs High level language constructs Increase the level of abstraction and reuse the core transformationfunctions across language domains Aspect Weavers We use a commercial PTE from Semantic Designs (the Design Maintenance System - DMS)

  13. Current State-of-the-Art: Rewriting Techniques • object-based transforms, such as a visitor object applied to an object model • intermediate representations that permit primitive transformations to be applied to a set of languages (e.g., .Net CodeDOM) • XML-based transforms that use an XML DOM structure • term rewriting, such as a transformation rule

  14. Current State-of-the-Art:SourceWeave.Net • Uses Microsoft’s CodeDom Architecture as the underlying AST Representation • Uses XML descriptor to specify interaction between aspects and .Net components • Limited availability of • CodeDOM providers • CodeDOM biased towards • C#, hence lack of • expressiveness for other languages • Verbosity of XML representations a serious concern for scalability http:// aosd.net/2004/archive/JacksonPoster.pdf

  15. Current State-of-the-Art:Weave.Net • Uses existing .Net Binary Component and cross-cutting specifications in an xml file as input • Advice is given separately in another .Net assembly • Limited to applications • hosted within .Net • Aspect specification is difficult to • comprehend due to lack of expressiveness of XML constructs http://www.dsg.cs.tcd.ie/uploads/category144/119.pdf

  16. Current State-of-the-Art: Aspect Cobol • Parse trees are exported to XML • Weaving boils down to XML DOM tree processing in Java. • XML representation of source code (intermediate form) may not scale with code size • It has been reported that such internal representations are 50 times larger and much slower to transform [Ger01] • Limited only to COBOL i.e., a more generalized approach is missing Roy Germon, “Using XML as an Intermediate Form for Compiler Development,” XML Conference and Exposition, Orlando, FL, December 2001. http://homepages.cwi.nl/~ralf/AspectCobol/

  17. Current State-of-the-Art: Aspierce + GCC 4.0 • Proposes to use GCC 4.0 GENERIC trees • Weaving is done by modifying the GENERIC • AST representations • Lack of support for .Net Languages like C#, VB.Net and other languages like Object Pascal, Cobol etc • Still in a proposal stage, not clear whether API support is available for modifying GENERIC trees • Very little documentation available from project site http://users.ugent.be/~badams/publications/2005/language-independentaspectweaving.pdf

  18. Background:Term Rewriting Based Program Transformation • Term rewriting is a paradigm that is used in fields such as program transformation and theorem proving • In term rewriting, rules define a refinement to a structure by specifying a pattern to be matched and the resulting effect (closer to logic and algebraic programming) Example: privaterule refine_expression_add(e1:expression@InfixArithmetic, e2:expression@InfixArithmetic): expression -> expression = "+ \e1\:expression \e2\:expression" -> "(\e1) + (\e2)".

  19. Genericity of Aspect Transformations (Object Pascal) – Database Error Handler Synchronization DMS Rewrite Rule Object Pascal Source File …… rule sync_OP_meths (sl:stmt_list, id:IDENTIFIER, fps: formal_params, frt:func_result_type): qual_func_header_decl  qual_func_header_decl = "function \method_id\(\id\) \fps : \frt ; begin \sl end;"  "function \method_id\(\id\) \fps : \frt ; begin \LockStmt\(\); try \sl finally \UnLockStmt\(\); end;“ ……… function TExNullField.Handle (ServerType: TServerType; E: EDBEngineError): Integer; begin <database error handling code omitted here> end; ……… TExHandleCollection (Collection).LockHandle; try finally TExHandleCollection (Collection).UnLockHandle; end;

  20. Genericity of Aspect Transformations ( Java) – Database Error Handler Synchronization DMS Rewrite Rule Java Source File …… • rule sync_Java_meths (s_seq:stmt_seq,m_mods:meth_modifiers, • t:type,id:IDENTIFIER, • fp:fparams) : • method_declaration • method_declaration = • "\m_mods \type • \method_id\(\id\) \fp • { \s_seq } ;"  • "\m_mods \type • \method_id\(\id\) \fp • { \LockStmt\(\); • try { \s_seq } • finally { • \UnLockStmt\(\) } • };” ……… public Integer HandleDBError( TServerType ServerType, EDBEngineError E) { <database error handling code omitted here> } ErrHandlerCollction . LockHandle(Collection); try { finally { ErrHandlerCollection . UnLockHandle(Collection); }

  21. Transformation Map DMS Rewrite Rule for Java DMS Rewrite Rule for Object Pascal …… • rule sync_Java_meths (s_seq:stmt_seq,m_mods:meth_modifiers, • t:type,id:IDENTIFIER, • fp:fparams) : • method_declaration • method_declaration = • "\m_mods \type • \method_id\(\id\) \fp • { \s_seq } ;"  • "\m_mods \type • \method_id\(\id\) \fp • { \LockStmt\(\); • try { \s_seq } • finally { • \UnLockStmt\(\) } • };” …… rule sync_OP_meths (sl:stmt_list, id:IDENTIFIER, fps: formal_params, frt:func_result_type): qual_func_header_decl  qual_func_header_decl = "function \method_id\(\id\) \fps : \frt ; begin \sl end;"  "function \method_id\(\id\) \fps : \frt ; begin \LockStmt\(\); try \sl finally \UnLockStmt\(\); end;“

  22. Language-Parametric Synchronization Rule – Intermediate AST Mapping to Intermediate AST Generic Transformation Rule rule sync_generic (sL:st_list, i:ID_list, pl: param_list, rt:ret_type): std_func_decl -> std_fun_decl = "meth_signature(\id\,\pl\,\rt) \std_start \sL \std_end" -> "meth_signature(\id\,\pl\,\rt) \std_start \LockStmt\(\); \try_finally_decl \sL \UnLockStmt\(\); \std_end“ st_list@iAst  stml_list@OP ID_list@iAst  id@OP param_list@iAst  paramformal_params@OP ret_type@iAst  func_result_type@OP meth_signature@iAst  qual_func_header_decl@OP ---------------------------- st_list@iAst  stmt_seq@Java ID_list@iAst  id@Java param_list@iAst  fparams@Java ret_type@iAst  type@Java meth_signature@iAst  method_declaration@Java

  23. System Workflow Input Source File Intermediate AST Reader Symbol Table AST Graph Lexer/ Parser parser definitions Lexer/ Parser Attribute Evaluator AST Graph Pattern Transformer Analyzer Domain Reader Revised Source File Transformation Engine Pretty Printer unparser definitions Core Transforms Generic Transforms Transformation Engine Phase 1 Phase 2

  24. GenAWeave in Action Input Source File Intermediate AST Reader Symbol Table AST Graph Lexer/ Parser parser definitions Lexer/ Parser Attribute Evaluator AST Graph Pattern Transformer Analyzer Domain Reader Revised Source File Transformation Engine Pretty Printer unparser definitions Core Transforms Generic Transforms Transformation Engine Phase 1 Phase 2

  25. GenAWeave in Action Input Source File Intermediate AST Reader Symbol Table AST Graph Lexer/ Parser parser definitions Lexer/ Parser Attribute Evaluator AST Graph Pattern Transformer Analyzer Domain Reader Revised Source File Transformation Engine Pretty Printer unparser definitions Core Transforms Generic Transforms Transformation Engine Phase 1 Phase 2

  26. GenAWeave in Action Input Source File Intermediate AST Reader Symbol Table AST Graph Lexer/ Parser parser definitions Lexer/ Parser Attribute Evaluator AST Graph Pattern Transformer Analyzer Domain Reader Revised Source File Transformation Engine Pretty Printer unparser definitions Core Transforms Generic Transforms Transformation Engine Phase 1 Phase 2

  27. GenAWeave in Action Input Source File Intermediate AST Reader Symbol Table AST Graph Lexer/ Parser parser definitions Lexer/ Parser Attribute Evaluator AST Graph Pattern Transformer Analyzer Domain Reader Revised Source File Transformation Engine Pretty Printer unparser definitions Core Transforms Generic Transforms Transformation Engine Phase 1 Phase 2

  28. GenAWeave in Action Input Source File Intermediate AST Reader Symbol Table AST Graph Lexer/ Parser parser definitions Lexer/ Parser Attribute Evaluator AST Graph Pattern Transformer Analyzer Domain Reader Revised Source File Transformation Engine Pretty Printer unparser definitions Core Transforms Generic Transforms Transformation Engine Phase 1 Phase 2

  29. GenAWeave in Action Input Source File Intermediate AST Reader Symbol Table AST Graph Lexer/ Parser parser definitions Lexer/ Parser Attribute Evaluator AST Graph Pattern Transformer Analyzer Domain Reader Revised Source File Transformation Engine Pretty Printer unparser definitions Core Transforms Generic Transforms Transformation Engine Phase 1 Phase 2

  30. GenAWeave in Action Input Source File Intermediate AST Reader Symbol Table AST Graph Lexer/ Parser parser definitions Lexer/ Parser Attribute Evaluator AST Graph Pattern Transformer Analyzer Domain Reader Revised Source File Transformation Engine Pretty Printer unparser definitions Core Transforms Generic Transforms Transformation Engine Phase 1 Phase 2

  31. GenAWeave in Action Input Source File C4 Intermediate AST Reader C1 Symbol Table C2 AST Graph Lexer/ Parser parser definitions Lexer/ Parser C4 C2 C2 Attribute Evaluator AST Graph Pattern Transformer Analyzer Domain Reader Revised Source File Transformation Engine Pretty Printer unparser definitions Core Transforms Generic Transforms C4 Transformation Engine C3 C1 Phase 1 Phase 2

  32. Aspect Layering – Challenge C5 • Remove accidental complexities arising from term rewriting • Provide an easy customized aspect language using the • Join Point Model (JPM) adapted from AspectJ • The formalizations of transformation rules showed the • relationship between the JPM model of an aspect language • with respect to rewrite rules aspectgeneric_synchronize { before(): execution (mname@meth_signature) { // insert base language specific lock statement } after(): execution (mname@meth_signature) { // insert base language specific unlock statement }

  33. Object Management Group(OMG) ASTM –Abstract Syntax Tree Meta-model “ It has long been observed that although there are many differences between the statements in many programming languages there is a very large set of statements that are common across most languages. The Object Management Group (OMG) Architecture Driven Modernization Task Force has issued an RFP for the Abstract Syntax Tree Meta Modeling standard. The ASTM seeks to establish a single comprehensive set of modeling elements for capturing how many software languages represent the same software language constructs and concepts…”

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