Supporting Software Development through Declaratively Codified - - PowerPoint PPT Presentation

SEKE 2001 - 14 June

VUB Brussels - Belgium

Supporting Software Development through Declaratively Codified Programming Patterns

Kim Mens, Isabel Michiels and Roel Wuyts

Vrije Universiteit Brussel (VUB), Belgium

SEKE 2001 - 14 June

VUB Brussels - Belgium

Table of Contents

• Introduction
• Our Approach
• Declarative Meta-Programming (DMP)
• Codifying Programming Patterns

Best practice patterns, design patterns, …

• Supporting Software Development
• Tool Support
• Conclusion

SEKE 2001 - 14 June

VUB Brussels - Belgium

Introduction

• Software development

– Incremental process – Large development teams

• Readability of software is crucial
• Use commonly accepted programming patterns to

make programmer’s intent clear

• However…

No explicit support in programming language nor in the environment

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Our Approach

• Codify programming patterns in a declarative

language

• Make explicit link between declarative language

and programming language

• Use declarative reasoning to:

– check & search – detect violations – generate code

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Declarative Meta-Programming (DMP)

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The representational mapping (1)

An example:

Rule ule class(?Class) if if constant(?Class), [Smalltalk includes: ?Class name]. Rule Rule class(?Class) if if variable(?Class), generate(?Class,[Smalltalk allClasses]) Query class([Array]).

smalltalk code used as a predication has to return true

• r false

smalltalk code used in a generate predicate has to return a collection of results

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The representational mapping (2)

Examples of other SOUL predicates:

class(?Class) classImplementsMethod(?Class,?MethodName,?Method) methodArguments(?Method,?Arglist) methodClass(?Method,?Class) methodName(?Method,?Name) methodStatements(?Method,?StatementList) instVar(?Class,?InstVarName) isSentTo(?SenderClass,?ReceiverClass,?MesgName,?Arglist)

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Codifying Best Practice Patterns

• Example:
• Getting Method: how do you provide access to an instance variable?

Rule gettingMethod(?Class,?Method,?InstVar) if classImplementsMethod(?Class,_,?Method), instVar(?Class,?InstVar), methodName(?Method,?InstVar), gettingMethodStats(?Stats,?InstVars), methodStatements(?Method,?Stats).

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Codifying Design Patterns

Example: Visitor Design Pattern Rule Rule visitor(?Visitor,?El,?AcceptM,?VisitSelector) if if classImplementsMethod(?Visitor,?VisitSelector,_), classImplementsMethod(,?El,?AcceptM,?Meth), methodStatements( ?Meth, <return(send(?V,?VisitSelector,?VisitArgs))>), member(variable([#’self’]),?VisitArgs), methodArguments(?Meth,?AccArgs), member(?V,?AccArgs).

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Codifying Design Patterns (2)

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Codifying other Programming Patterns

Example: [Riel’s Design Heuristics] All abstract classes must be base classes and all base classes should be abstract classes. Rule Rule abstractClassHeuristic() if if forall(abstractClass(?Class),baseClass(?Class)), forall(baseClass(?Class),abstractClass(?Class)).

SEKE 2001 - 14 June

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Supporting Software Development (1)

• checking and searching

search for Getting Method:

Query Query gettingMethod([ApplicationModel],?M,[#’builder’]) Query ry gettingMethod([ApplicationModel],?M,?InstVar) Query ery gettingMethod(?Class,?Method,[#’name’])

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Supporting Software Development (2)

• detecting violations

Rule accessingviolator(?Class,?Meth,?InstVar,?ViolMsg) if instVar(?Class,?InstVar), classImplementsMethod(?Class,_,?Meth), not(gettingMethod(?Class,?Meth,?InstVar)), isSentTo(?Class,variable(?InstVar),?ViolMsg,_). Query accessingViolator(?Class,?Meth,?InstVar,?Msg)

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Supporting Software Development (3)

• Generating code

Rule generateAccessor(?Class,?InstVar) if instVar(?Class,?InstVar), not(classImplementsMethod(?Class,?InstVar,_)), gettingMethodStats(?Stats,?InstVar), generateMethod( method(?Class,?InstVar,<>,<>,?Stats)).

“Generate code from the method parse tree description”

“Check whether ?InstVar not

already exists”

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Tool Support

• well-integrated and user-friendly tools to integrate

SOUL in a development environment

• Possible (and existing) tools:

– synchronization between design and implementation of software (using the synchronization framework) – structural find application – to do application

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Conclusion

• Use of programming patterns is crucial for

software development support

• need for tools to support these patterns
• our approach: use DMP as a medium
• DMP is ideal for this:

– it is declarative – logic language benefits (multi-way reasoning, unification, backtracking) – base-language independent – it is customizable

• we reach a higher level of abstraction of code

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References

[1] K Beck. Smalltalk Best Practice Patterns. Prentice Hall PTR, 1997. [2] M. Fowler. Refactoring: Improving the Design of Existing

• Program. Addison Wesley, 1999

[3] R. Wuyts. Declarative Reasoning about the Structure of Object-Oriented Systems. In proceedings of TOOLS USA

• 1998. IEEE Computer Society Press, 1998.