Research On Extraction Method Of Design Patterns Based On Ontology

Design pattern is a kind of important means to express object-oriented softwaresystem design experience which expressed by identifying objects, cooperation andresponsibility assignment between objects.Design patterns are widely used in variousareas of the development of large-scale software system when it is instantiated.Designpattern extraction means to identify design patterns instance from program throughreverse engineering method.This extraction process is a conversion from a concreterepresentation to a abstract expression.Research on design pattern extraction is ofgreat significance not only for the improvement of software understandability andreusability,but also for the recovery of software architecture.And it’s also a effectiveway to keep the consistency of documents and programs in each iteration and toevaluate the quality of the software development.Many beginners of software designoften try to apply software design knowledge that has similar background with currentproject to current software development.This can reduce the design complexity andenhance efficiency.In the basis of existing method of software design knowledge extraction,thispaper puts forward a kind of design pattern extraction method based on ontology anddoes in-depth research. The main work of this paper are as follows:1.Propose a design pattern representation method based on description logic.Weanalyse the structure and information of design pattern,then use ALCQ language todescribe design pattern.ALCQ is a kind of description logic language that containsexistential quantifier constraints.This paper gives concept constructors which issuitable for the expression of design pattern,and defines the basic concept and basicrelationship about design pattern.Then we can use the concept constructors and basicrelationship to connect basic concept to get complex concept.We can get fullydescription logic representation of design pattern by the way of constructing complex concept from simple concept.2.Use Protégé tool to build design pattern ontology library.It’s convenient tobuild ontology based on OWL language to use visual ontology-edit tool Protégé.Theconcept in description corresponds to the class in OWL,and the relationship betweenconcept corresponds to property of OWL. So using Protégé,we can build ontologylibrary based on the description logic representation of design pattern.3.About extraction of program source code information,we first use JavaCC togenerate a parser for Java language,then use the parser to parse source code to getabstract syntax tree,finally obtain the information about classes and relationships ofclasses by traversing the syntax tree.These information will be store in files whichwill be the input of reasoner.4.Use ontology reasoner to reason and identify design patterns in theprogram.Reasoner reads the information extracted from code to be input ofreasoner,then classify the instance based on the ontology library which defined rulesof each design pattern.The reasoning process first classify sentence-level instance tosentence-level concept,second classify method-level instance to method-levelconcept,then classify class-level instance to class-level concept,finally classifyprogram instance to some kinds of design patterns according each classes’ categoryand their relationships.