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Research Directions Towards

Software Maintenance, Adaptation

and Modernization Grammar-based Software Technology -

Spring 2006 Programming Lang. Seminar

Suman Roychoudhury

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Maintaining Legacy Code – Tool Support ?

Cobol

Legacy

Software

Fortran

Object Pascal

Commercial + Scientific Applications

200 Billion Lines of Cobol Source

Migration is not an easy task !

Infrastructure, money effort already spent

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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

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Aspect Weavers: Current Limitations

However –

1. Specific to a few popular languages (e.g., Java)

2. New tools are developed from scratch without preserving knowledge of previous construction

3. No emphasis on re-usability in a different language and platform context

Several tools and language extensions have been developed to enable aspect weaving :-

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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?

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Challenges in Language-Parametric Legacy AdoptionChallenge 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

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Challenge C1 – The Parser Construction Problem

IntermediateSyntax

IntermediateType

Analysis

Parser ConcreteSyntax

Aspect Language

Transformation System

User Inputs

Legacy System

Scalabilty Extensibility Availabilty of

AST Framework

Reusabilty C++ Object Pascal Fortan Cobol Ada Jovial VHDL

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Parser ConcreteSyntax

Aspect Language

Transformation System

User Inputs

Legacy System

Challenge C2 – Type Analysis Problem

IntermediateSyntax

IntermediateType

Analysis

Interaction of aspects with Type System (e.g. computing sub-types for a given type)

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Challenge C3 – The Code Transformation Problem

IntermediateSyntax

IntermediateType

Analysis

Parser ConcreteSyntax

Aspect Language

Transformation System

User Inputs

Legacy System

patternpattern probe_id_pattern1() probe_id_pattern1(): : unqualified_idunqualified_id = " printf ". = " printf ".

rulerule insert_probe1 insert_probe1(s: (s: statement_seqstatement_seq): ): function_bodyfunction_body ->-> function_bodyfunction_body = " { \s } " = " { \s } " ->-> "{ \probe_id_pattern1\(\)"{ \probe_id_pattern1\(\) (\"Entering Method…\");(\"Entering Method…\"); { \s } { \s } }".}".

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Parser ConcreteSyntax

Aspect Language

Transformation System

User Inputs

Legacy System

Challenge C4 – Language-Parametric Generalization of Transformation Objectives

IntermediateSyntax

IntermediateType

Analysis

patternpattern probe_id_pattern1() probe_id_pattern1(): : IUnqualifiedIdIUnqualifiedId = "IFunctionName". = "IFunctionName".

rulerule insert_generic_probe1 insert_generic_probe1(s: (s: IStatementListIStatementList): ): IFunctionDeclIFunctionDecl ->-> IFunctionDeclIFunctionDecl = " \Block_Begin= " \Block_Begin \s \s \Block_End" \Block_End" ->-> "\Block_Begin"\Block_Begin \probe_id_pattern1\(\)\probe_id_pattern1\(\) (\"Entering Method…\");(\"Entering Method…\"); \Block_Begin\Block_Begin \s \Block_End\s \Block_End

\Block_End\Block_End ".".

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Challenge C5 – Accidental Complexities of Transformation Specifications

IntermediateSyntax

IntermediateType

Analysis

Parser ConcreteSyntax

Aspect Language

Transformation System

User Inputs

Legacy System

A high level aspect language layered on top of the base system

Translates to low level specifications

aspect insert_probe1 { before(): execution (function_declaration) { // insert print statement } }

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Goal Statement

Program Transformation

System(C1,C3)

Aspect Weavers

Low Level xForm constructs

High level language constructs

Legacy Software

Increase the level of

abstraction and reuse the

core transformation

functions across language

domains

Parametric Transforms

Goal 1 : Raise the level of abstraction (aspect layering) for end-programmers (C5)

Goal 2 : Re-use core transformations across language domains using language parametric transforms (C2, C4)

We use a commercial PTE from Semantic Designs (the Design Maintenance System - DMS)

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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

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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

http:// aosd.net/2004/archive/JacksonPoster.pdf

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

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Current State-of-the-Art:Weave.Net

http://www.dsg.cs.tcd.ie/uploads/category144/119.pdf

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

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Current State-of-the-Art: Aspect Cobol

http://homepages.cwi.nl/~ralf/AspectCobol/

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.

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Current State-of-the-Art: Aspierce + GCC 4.0

http://users.ugent.be/~badams/publications/2005/language-independentaspectweaving.pdf

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

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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)

private rule refine_expression_add(e1:expression@InfixArithmetic, e2:expression@InfixArithmetic):expression -> expression= "+ \e1\:expression \e2\:expression" -> "(\e1) + (\e2)".

Example:

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Genericity of Aspect Transformations (Object Pascal) – Database Error Handler Synchronization………

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;

……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;“

Object Pascal Source File DMS Rewrite Rule

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Genericity of Aspect Transformations ( Java) – Database Error Handler Synchronization………

public Integer HandleDBError( TServerType ServerType,

EDBEngineError E)

{

<database error handling code omitted here>

}

ErrHandlerCollction

. LockHandle(Collection);

try {

finally {

ErrHandlerCollection

. UnLockHandle(Collection);

}

……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\(\) } };”

Java Source File DMS Rewrite Rule

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Transformation Map……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;“

DMS Rewrite Rule for Object PascalDMS Rewrite Rule for Java

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Language-Parametric Synchronization Rule – Intermediate AST

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@JavaID_list@iAst id@Javaparam_list@iAst fparams@Javaret_type@iAst type@Javameth_signature@iAst method_declaration@Java

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“

Generic Transformation RuleMapping to Intermediate AST

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System Workflow

Lexer/Parser

Pattern Transformer

Intermediate AST Reader

Attribute Evaluator

Symbol Table

Transformation Engine

Pretty Printer

Analyzer

Transformation Engine

Generic Transforms

CoreTransforms

Lexer/Parser

Domain Reader

InputSourceFile

RevisedSourceFile

ASTGraph

ASTGraph

unparser definitions

parserdefinitions

Phase 1 Phase 2

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GenAWeave in Action

Lexer/Parser

Pattern Transformer

Intermediate AST Reader

Attribute Evaluator

Symbol Table

Transformation Engine

Pretty Printer

Analyzer

Transformation Engine

Generic Transforms

CoreTransforms

Lexer/Parser

Domain Reader

InputSourceFile

RevisedSourceFile

ASTGraph

ASTGraph

unparser definitions

parserdefinitions

Phase 1 Phase 2

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GenAWeave in Action

Lexer/Parser

Pattern Transformer

Intermediate AST Reader

Attribute Evaluator

Symbol Table

Transformation Engine

Pretty Printer

Analyzer

Transformation Engine

Generic Transforms

CoreTransforms

Lexer/Parser

Domain Reader

InputSourceFile

RevisedSourceFile

ASTGraph

ASTGraph

unparser definitions

parserdefinitions

Phase 1 Phase 2

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GenAWeave in Action

Lexer/Parser

Pattern Transformer

Intermediate AST Reader

Attribute Evaluator

Symbol Table

Transformation Engine

Pretty Printer

Analyzer

Transformation Engine

Generic Transforms

CoreTransforms

Lexer/Parser

Domain Reader

InputSourceFile

RevisedSourceFile

ASTGraph

ASTGraph

unparser definitions

parserdefinitions

Phase 1 Phase 2

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GenAWeave in Action

Lexer/Parser

Pattern Transformer

Intermediate AST Reader

Attribute Evaluator

Symbol Table

Transformation Engine

Pretty Printer

Analyzer

Transformation Engine

Generic Transforms

CoreTransforms

Lexer/Parser

Domain Reader

InputSourceFile

RevisedSourceFile

ASTGraph

ASTGraph

unparser definitions

parserdefinitions

Phase 1 Phase 2

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GenAWeave in Action

Lexer/Parser

Pattern Transformer

Intermediate AST Reader

Attribute Evaluator

Symbol Table

Transformation Engine

Pretty Printer

Analyzer

Transformation Engine

Generic Transforms

CoreTransforms

Lexer/Parser

Domain Reader

InputSourceFile

RevisedSourceFile

ASTGraph

ASTGraph

unparser definitions

parserdefinitions

Phase 1 Phase 2

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GenAWeave in Action

Lexer/Parser

Pattern Transformer

Intermediate AST Reader

Attribute Evaluator

Symbol Table

Transformation Engine

Pretty Printer

Analyzer

Transformation Engine

Generic Transforms

CoreTransforms

Lexer/Parser

Domain Reader

InputSourceFile

RevisedSourceFile

ASTGraph

ASTGraph

unparser definitions

parserdefinitions

Phase 1 Phase 2

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GenAWeave in Action

Lexer/Parser

Pattern Transformer

Intermediate AST Reader

Attribute Evaluator

Symbol Table

Transformation Engine

Pretty Printer

Analyzer

Transformation Engine

Generic Transforms

CoreTransforms

Lexer/Parser

Domain Reader

InputSourceFile

RevisedSourceFile

ASTGraph

ASTGraph

unparser definitions

parserdefinitions

Phase 1 Phase 2

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GenAWeave in Action

Lexer/Parser

Pattern Transformer

Intermediate AST Reader

Attribute Evaluator

Symbol Table

Transformation Engine

Pretty Printer

Analyzer

Transformation Engine

Generic Transforms

CoreTransforms

Lexer/Parser

Domain Reader

InputSourceFile

RevisedSourceFile

ASTGraph

ASTGraph

unparser definitions

parserdefinitions

C2

C2

C4

C4

C4

C3

C2

C1

C1

Phase 1 Phase 2

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Aspect Layering – Challenge C5

aspect generic_synchronize { before(): execution (mname@meth_signature) { // insert base language specific lock statement } after(): execution (mname@meth_signature) { // insert base language specific unlock statement }

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

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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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