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定分野への適用に関する研究

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Hiromitsu Shimizu

Scho ol of Information Science,

Japan Advanced Institute of Science and Technology

Februaly 14, 1997

Keywords: object-oriented design, reuse, designpatterns, frameworks.

The advantage ofobject-orienteddesign,whichmakesabstractiontoreal worldusing

objects and designs software, is reusability. Though there is reusable, designing object-

orientedsoftwareishard,becauseyoumustndpertinentobjects,factorthemintoclasses

at the right granularity,dene class interfaces and inheritance hierarchies, and establish

key relationshipsamong them.

Design patterns are reusable and systematically explains reccurring design inobject-

oriented design. Each design pattern systematically names, explains and evaluates an

importantand recurring design in object-oriented systems. Design patternsmakeit eas-

ier to reuse successful designs and architectures. Design patterns can even improve the

documentation and maintenance of existing systems by furnishing an explicit specica-

tion of class and object interactions and their underlying intent. It is a partially proved

that each of design patternsfor general purpose isuseful. But, designpatterns are more

abstract, and howthose apply specicdomain isn't studied enough. So, this paper show

a case study for building framework, which is a set of co operating classes that make up

a reusabledesign for aspecicclass of software are discussed. Applying design patterns,

and guess problems with reusabledesigning. A frameworkis a setof cooperatingclasses

that make up a reusable design for a specic class of software, and most reusable in

object-oriented component.

We apply the approachto designing programming language pro cessor. Programming

language processor established in its design and apply various area. A target systems

consist of the sub-systems including scannar (lexical analyser), parser, evaluator and

viewer.

Wediscussthat the essentialp ointindesigning frameworkforprogramming language

processor are as follows: (1) extendability of grammar: Grammar symb ol incontext-free

Copyright c

1997byHiromitsuShimizu

some property. Sogrammar mustbe able to change. (2) exibility inoutput: Outputof

parser area parse tree andanabstract syntax tree. Nodeof themvarysinlanguage, but

a way of building parse tree is xed. And a way of building abstract syntax tree mayb e

changedthat is not changing a kind of node handled in language. Therefore framework

must be able to easily change a way of building abstract syntax tree. (3) Use semantic

rule: To describe attribute grammar in used of static semantics which is dicult that

prove in context-free grammar. Generally, attribute grammar may have a various typ e.

Soframework mustbe able to handleexible typ e of attributes.

Theresultofanalysingrequireforprogramminglanguageprocessor,aboutstructureof

framework,designpatternsisusableasfollows: (1) Using Interpreterpattern, framework

declared a property of eachexpression of terminal symb ol and non-terminalsymb ol,and

grammar symb ol expression is inheriting them. So this pattern allows to change gram-

mar, can output a parse tree after parsing and provide a way of semantic analysis. (2)

Builder pattern separates abstractsyntax tree builderfrom grammar symbol expression,

so framework allows to change to a way of building abstract syntax tree. And making

abstraction of a class required in semantic analysis, framework allowsto change to typ e

of attribute. (3) Iterator pattern take the responsibility for access and traversal out of

anaggregateobjectwhichislistexpressedattributeorparse treeorabstractsyntaxtree,

make traverse without exposing its internal structure, and allows to change to a way of

traversal.

After abstract classes structured framework prop osed in this paper inherits and im-

plements application of programming language processor, for testingframework that it's

design isreasonable,we giveanexample ofsimple programming language processor, and

application which applied framework designed and implemented. The result shows that

frameworkmakeiteasytoimplementit. Especially,weshowthattheparsercan b ebuilt

by the grammar automatically. Therefore, we show that framework captures almost of

the designdecisions thatrequired inbuilding applications ofprogramming language pro-

cessor. If we use design patternsand building systems with them, design patternswhich

cansolvethedesignproblem intargetsystems. Wemustevaluatethe resultofusingthat

pattern, whether itis applicable under condition of it. Soin applyingdesign patterns to

specic domain, precise documentation isuseful to build similarsystems. And therefore,

application of design patternsto problems which itgives nodirect supports for is future

work.