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云计算环境下海量RDF数据管理系统核心技术研究 2011年亚太地区互联网技术会议 纳米铁系材料处理氯酚类污染物的机理研究 新双核配体化合物在固氮研究中的应用 影响聚合物光伏器件填充因子的结构与动力学因素研究
杜小勇 杜小勇 程荣 曹睿 艾希成
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International Journal of Educational Development 24(2004)677–690/locate/ijedudevA professional development program for primary schoolEnglish language teachers in Turkey:designinga materials bankAys ¸egu }l Daloglu ÃDepa rtment of Foreign La ngua ge Educa tion,Middle Ea st Ea st Technica l University,06531Anka ra ,TurkeyAbstractThis paper presents and discusses an in-service teacher development program that focussed on establishing a mate-rials bank for English language teachers at a private primary school in Ankara,Turkey,and teachers’evaluations ofthe program.The program aimed to lead to teacher change as growth and learning,to address school-based needs,and to provide overall quality improvement.Feedback obtained during the professional development program and after its completion demonstrates that teachers improved their knowledge and skills on materials design and curricu-lum related issues as well as improving the overall quality of instruction and developing a positive attitude towards professional development.#2004Elsevier Ltd.All rights reserved.Keywords:Professional development;Designing instructional materials1.IntroductionTeachers’continuing professional development is important for the well being of schooling and quality improvement in teaching.Characteristics of effective professional development activities have changed over the course of time and show differences based on the educational context.However,unless they are rooted in sound theories of learning,much of what is considered to be in-service teacher development does not reach its aims,especially when the professional develop-ment of English language teachers is considered.In Turkey,the common understanding and prac-tice of in-service teacher development is a series of topically unrelated workshops over the course of an academic year.While attending such events is compulsory for teachers in some schools,it is optional in others.In either case,participating teachers report limited benefit from them as,in most situations,topics for in-service development programs are selected by people other than the teachers for whom the in-service is intended.Consequently,in-service programs rarely address individual needs and concerns.In addition to this,follow-up support for ideas and practices introduced in in-service programs occurs in only a very small minority of cases.These observations parallel the conclusions Fullan (1979)and Fullan and Stiegelbauer (1991)reached about ineffectiveÃTel.:+90-312-210-4085;fax:+90-312-210-1256.E-mail address:daloglu@.tr (A.Daloglu)0738-0593/$-see front matter #2004Elsevier Ltd.All rights reserved.doi:10.1016/j.ijedudev.2004.04.001in-service teacher development more than20 years ago and suggest that there is a lack of con-ceptual basis in the planning and implementing of in-service programs that would ensure their effec-tiveness if‘‘teacher change’’that is induced through the professional development is to lead to growth and learning.This paper presents the characteristics of a specific in-service professional development program that was designed in response to a school-based need and the partic-ipating teachers’evaluations of the program.2.In-service professional development and teacher changeOne of the issues commonly discussed is the extent to which in-service teacher education leads to teacher change.Clarke and Hollingsworth (2002,p.948)describe six perspectives on teacher change:.Change as training:Change is something that is done to teachers;that is,teachers are ‘‘changed’’..Change as adaptation:Teachers‘‘change’’in response to something;they adapt their practi-ces to changed conditions..Change as personal development:Teachers ‘‘seek to change’’in an attempt to improve their performance and develop additional skills or strategies..Change as local reform:Teachers‘‘change something’’for reasons of personal growth..Change as systemic restructuring:Teachers enact the‘‘change policies’’of the system..Change as growth or learning:Teachers ‘‘change inevitably through professional activity’’;teachers are themselves learners who work in a learning community.Most of these perspectives on change are not mutually exclusive;moreover,many are inter-related.Clarke and Hollingsworth(2002)suggest that the central focus of professional development efforts aligns with‘‘change as growth or learning’’perspective.Within this perspective,change is identified with learning.In addition,it is seen as a natural and expected component of the pro-fessional activity of teachers.In Turkey,until recently,professional development of teachers was viewed as teacher training where develop-ment of knowledge and skills was emphasized.As a result,most teacher development activities con-sisted of one-shot workshops that aimed to foster mastery of prescribed skills and knowledge.Pro-fessional development activities provided in this format have been criticized widely in literature. For example,researchers like Guskey(1985, 1986)and Wood and Thompson(1980)believe in the ineffectiveness of professional development programs that are based on the assumption that teachers lack certain skills and knowledge needed by the profession.In addition to these research-ers,Fullan and Stiegelbauer(1991)and Lovitt and Clarke(1988)provide convincing evidence that‘‘one-shot’’professional development activi-ties fail to induce long-lasting changes in teacher behaviour.In light of the convincing evidence on ineffec-tiveness of‘‘one-shot’’professional development activities,the focus of research has shifted to pro-cess of change.Rather than viewing change as something that is done to teachers,change is seen as a complex process that involves learning.In this view,teachers are no longer passive recipients of training and education but they are active learners who participate through inquiry,skill, reflection,and collaboration in the professional development programs and practice(Pennington, 1996;Williams and Burden,1997;Fullan and Stiegelbauer,1991;Guskey,1986;Johnson,1996). This shift in focus of teacher development has placed growing emphasis on on-going and life-long professional learning for teachers.As Jack-son(1974)states,teacher motivation to learn is not to repair a personal inadequacy but to ach-ieve‘‘greater fulfilment as a practitioner of the art’’(p.24).Likewise,Schon(1983)emphasises the importance of ongoing critical reflection as teachers become reflective practitioners.In view of professional development where teachers are seeking fulfilment through reflection and pro-fessional development,change is realised as growth or learning and teachers themselves are learners in a learning community.As Clarke and Hollingsworth(2002)state,‘‘it appears that fun-A.Daloglu/International Journal of Educational Development24(2004)677–690 678damental to new perspectives on teacher change and professional development that have learning as their core are views of‘teachers as learners’and‘schools as learning communities’’’(p.949). One point that needs to be considered is how the process of teacher change is addressed in pro-fessional development programs.‘‘One-shot’’workshops usually attempt to change teachers’beliefs and attitudes with the hope that such changes will lead to changes in classroom practi-ces(Fullan,1982).This perspective is based on the assumption that the underlying motivation for any teacher development activity is improving students’learning outcomes.Guskey(1986),how-ever,points out that teachers’beliefs and atti-tudes are more likely to change only after improvement in student learning outcomes have become evident.More specifically,teachers change their beliefs and attitudes if changes in teachers’classroom practices lead to changes in student learning outcomes.Clarke and Peter(1993)developed a model that views a teacher’s change environment in four domains that constitute the teacher’s world:per-sonal domain(teacher’s knowledge,beliefs,and attitudes),external domain(sources of support and information provided to the teacher),domain of practice(professional experimentation),and domain of consequence(observable outcomes such as student learning).According to this model,change occurs through the mediating processes of‘‘reflection’’and‘‘enactment’’where change in one domain leads to change in another. Professional development is viewed as a complex and inevitable process of learning that results from the mediating interaction among the domains.The context in which teachers work(their change environment)also has a considerable impact on their professional growth.The school context,according to Clarke and Hollingsworth (2002),influences every stage of the professional development process through four mechanisms: access to opportunities of professional develop-ment;restriction or support for particular types of participation;encouragement or discourage-ment for experiment with new teaching techni-ques;and administrative restrictions or support in the long-term application of new ideas.In other words,the school context can be very conducive to professional growth if teachers are provided access to professional development activities in which they are encouraged to participate;and if they are provided administrative support and encouragement to experiment with new teaching techniques and long-term application of ideas. Therefore,it is possible to conclude that,for professional development activities to lead to teacher change as growth or learning,programs need to be.based on the immediate needs of teachers,.embedded in the reality of school life,.participatory(designed and directed with teachers’input),.coherent and long range,.adequate to facilitate growth,critical reflec-tion,and change,and.integrated with an articulated vision for stu-dents.3.Role of instructional materials in achieving curricular goalsIn a very simple way,materials are defined as ‘‘any systematic description of the techniques and activities to be used in classroom teaching (Brown,1995,p.139).Such a definition is broad enough to encompass lesson plans,books,audio-visual aids,games,or any type of activity that can be used for language teaching and practising purposes.Cunningsworth(1995,p.7)summarizes the role of materials in language teaching as:.A source for presentation material(written or spoken).A source of activities for learner practice and communicative interaction.A reference source for learners on grammar, vocabulary,pronunciation,and so on.A source of stimulation and ideas for class-room activities.A syllabus(where they reflect learning objec-tives that have already been determined)679A.Daloglu/International Journal of Educational Development24(2004)677–690.A support for less experienced teachers who have yet to gain in confidenceAlthough this definition includes a wide range of teaching tools like Brown’s definition,it also focuses on the purposes of materials.Before actually developing materials,the insti-tution’s overall approach to language teaching should be considered as this orientation directly influences the choices that have to be made in the design and implementation of materials.Brown’s (1995)four categories of language teaching activi-ties that form the backbone of his model on a systematic approach to language program devel-opment are useful in explaining the role of mate-rials in the overall curriculum.In Brown’s model, thefirst category in language teaching activities refers to ways of defining needs which he calls approaches.The approach to language teaching and learning specifies‘‘ways of what and how students need to learn’’(Brown,1995,p.5).The second category in Brown’s model refers to organizing the course and materials,which he calls syllabuses.Regardless of the approach adopted,the syllabus provides a focus for what should be studied along with a rationale for how the content should be selected and ordered (McKay,1978).Structural,situational,topical, functional,notional,skills,and task are the most commonly used syllabus types in language teach-ing.In real life situations,two or three types of syllabus may be mixed together or there may be a secondary or even a tertiary syllabus operating under the primary syllabus,which Brown(1995) calls a mixed or a layered syllabus.The third cat-egory in Brown’s model is techniques—ways of presenting the language to the learners.The approach used to define learners’needs and the syllabus selected for organizing the materials affects the techniques that are chosen,but,still,a wide variety of techniques can be used within a certain approach or a syllabus.The fourth and thefinal category in Brown’s model is exercises or ways of practicing the language.The materials design in this model takes place in the categories of techniques and exercises since,at these stages, the guiding principles and values identified in the approaches and syllabuses are transferred to the teaching and learning environment through instructional materials.As a result,materials form the link between the institution’s edu-cational philosophy and the instructional process. Also,since the materials are based on the objec-tives of the syllabus,the materials lead to the realisation of curricular goals.Considering this central role of materials,it is possible to conclude that,through ensuring quality in materials,we can improve the quality of instruction while achieving the curricular goals.4.Developing an in-service professional development programThe in-service professional development pro-gram that is the focus of this article aimed to improve the quality of the instructional materials, a need that was jointly identified by teachers and their students.4.1.The contextThe professional development program was designed for the English language teachers who were teaching grades1–5at Turk Egitim Dernegi (TED)Ankara Koleji,a private primary and sec-ondary school that has a total of about6000stu-dents and422teachers.TED Ankara Koleji implements a bilingual curriculum where science, math,and English language and literature courses are carried out in English and the remaining courses are in Turkish,the students’native lan-guage.The main aim of employing a content-based curricular approach to English language education is to enable students to graduate with full communicative and academic proficiency in the English language in a country where English is the main foreign language.At the school,English language education starts in grade1by making the students familiar with the sounds of the language mostly through songs.After literacy skills in the native language are developed,students start to read and write in English in grade2.One of the main aims of Eng-lish language instruction in these early grades is to foster a positive attitude toward language learning and especially the English language.InA.Daloglu/International Journal of Educational Development24(2004)677–690 680grade3,students’vocabulary base is widened through stories.The overall goal of English lan-guage classes in grades4and5is to equip the students with the language skills and knowledge that is fundamental to their content learning in English.Due to the demands of this specific con-text,English language teachers face the challenge of developing near-native English language skills in their learners in a limited amount of time.The school provides in-service professional development opportunities to its teachers through its Research and Development Centre.The Research and Development Centre conducts annual needs analysis studies to diagnose the areas in which teachers would like to further develop themselves,identifies external specialists, and offers structured developmental opportunities led by the external specialists.4.2.Purpose and scope of the programThe in-service development program that is the focus of this article was established in response to feedback from teachers,students,administrators, and parents that,in English language courses, there were inconsistencies in the curriculum within and across grades.Specifically,the main concern was that there were considerable repeti-tions of instructional objectives and materials across grades,leading to situations where the same students encountered the same materials in more than one grade or there were significant gaps where some components of the curriculum were not covered at all in some classes.The spe-cific outcome of this lack of coherence was uncer-tainty about what language objectives students attained at the end of each grade and what instructional materials and techniques students had been exposed to.At the beginning of the2001–2002academic year,the professional development program which is the focus of this article was initiated and the researcher was asked to lead it as an external curriculum and materials development specialist who would guide the teachers in the process of identifying the specific problems and designing a program that would remedy the situation.There-fore,the starting point was identifying a set of common needs for the45teachers in lower pri-mary school(grades1–5)and their expectations from this in-service professional development program.4.2.1.Identification of specific needs and expectationsThefirst step in the professional development program was identifying the specific needs of teachers who would participate in this pro-fessional development program and their expect-ations from this program.In needs and expectations identification sessions that were con-ducted as various small group and whole group discussions,most teachers reported that they experienced communication problems that led to incoherent implementation of the curriculum.For example,a major problem was that many teach-ers reported spending a considerable amount of time trying to identify the linguistic and learning needs and competencies of the specific group of students they were teaching.In other words,they did not have sufficient information on the objec-tives covered in the previous year and the specific instructional techniques employed by the previous teacher of that specific group of students. Although there was a curriculum that all teachers were responsible for implementing,these dis-cussions led to the conclusion that,while making adaptations to address the specific needs of the learners,teachers could diverge from it to the extent of risking coherence.Another problem reported by the teachers was that,although there were course books adopted for each grade,there was a considerable need for teacher-made materi-als as the course books were,in some cases,inap-propriate for the specific group of learners. Preparing materials imposed time and expertise demands on the teachers.Also,the fact that some teachers devoted more time and energy than oth-ers to preparing supplementary materials led to inconsistencies among different classes in the same grade.At the end of various discussions,the institutional need that had highest priority and urgency was achieving coordination,coherence, and continuity in the curriculum across grades. The need that had second highest priority was establishing communication and collaboration681A.Daloglu/International Journal of Educational Development24(2004)677–690among teachers teaching different grades.The third need was identified as setting standards that ensure effectiveness of instructional materials,and the fourth need was establishing a system that enabled sharing of instructional materials. Based on these needs,developing a materials bank with an established system for classification, storage,evaluation,and maintenance was adopted as the main aim of the professional development program.The idea of establishing a materials bank gained the approval of nearly all of the teachers with the belief that initiating such a bank was an appropriate and concrete starting point that could lead to observable outcomes within a relatively short time frame of one aca-demic year.In addition to this,the process of establishing the materials bank,directly or indirectly,would lead to meeting the other insti-tutional needs as well.As a result,the overall aim of the professional development program was to set up a materials bank that would ensure.coordination and continuity in the curriculum, both within and across grades,.better meeting the learning needs of individual students,.sharing of instructional materials among col-leagues so the amount of time each teacher spends is reduced,.on-going and systematic evaluation of materi-als,and.improved communication among colleagues, leading to improved awareness on institutional issues.4.2.2.Structure of the professional development programThe external specialist who was also the researcher and all of the45English language teachers employed in thefirstfive grades at the school were involved in the development program in various ways.Due to the high number of parti-cipants and scheduling difficulties involved,each teacher participated in the development program by being a member of one of the following groups:.Core Group:Consisted of12teachers who attended the weekly workshops with the specialist.The regular teaching load of these teachers was reduced by3hours a week,the amount of time they were expected to invest in this program.These teachers had at least4 years of experience in this school,while the majority had been teaching for more than10 years.The head of the English department and grade coordinators who were responsible for preparing the progress exams were among the group members..Grade Groups:Consisted of4teachers teach-ing the same grade.Each Core Group member was the leader of a Grade Group,responsible for ensuring a smoothflow of information and knowledge from the Core Group to all of the teachers..Discussion Groups:Consisted of4teachers teaching different grades.Members of the Core Group were also members of Grade and Discussion groups;the teachers who were not in the Core group were members of both Grade and Discussion groups.Each group served a different purpose in achieving the aims of the project by providing their different per-spectives on the focal issues.Core Group mem-bers attended weekly sessions led by the external specialist.Then,each Core Group member trans-ferred these skills and knowledge to their col-leagues in their Grade Groups.4.2.3.Implementation of the professional development programThe professional development program aimed to provide input that would lead the participating teachers to a common understanding of effective materials and to provide opportunities for the practice of the skills acquired through the pro-gram.Therefore,the following action plan was devised:Step1:Definition of the characteristics of effec-tive materials for the specific teachingcontextStep2:Establish a system for classification,bor-rowing,maintenance,and evaluation ofmaterials in the bankA.Daloglu/International Journal of Educational Development24(2004)677–690 682Step3:Develop materials that adhere to the characteristics definedStep4:Pilot the materials in actual classrooms and revise them in light of feedbackobtainedStep5:Make the materials bank available to all teachersStep6:Evaluate the effectiveness of the materials bankThe professional development program consisted of three modules.4.2.3.1.Module1:Defining characteristics of effective materials The professional development program started out with making the participants familiar with the underlying principles of the communicative approach and the task-and skills-based syllabus—the approach and the syllabus adopted by the school.This activity was essential as the approach and the syllabus guide techniques and exercises employed in the materials(Brown, 1995).The next step in Module1was to identify the characteristics of effective and desirable Eng-lish language teaching materials.The Core Group members started this process byfirst identifying the categories for materials evaluation by refer-ring to Ellis(1998);Harmer(2001);Littlejohn (1998);McDonough and Shaw(1993)and Rea-Dickins and Germaine(1992)and came up with the following:.Purpose and curriculumfit.Texts and content.Tasks.Interest value.Variety and pace.Authenticity.Difficulty.Interaction patterns.Assessment of learning.Layout and visual appeal.PracticalityAfter the above categories were identified,a draft Materials Design Checklist that outlined the characteristics of effective materials was designed taking into consideration the institution specific priorities,values,and aims/needs.The group members identified being learner-centred,encour-aging interactive learning and learner self-assess-ment,promoting development of multiple learning styles and multiple intelligences,catering for the needs of mixed language ability classes, and developing a positive attitude towards lan-guage learning and the English language as the institutional priorities and values that were to be promoted through the materials.After the Core Group members shared the draft checklist with their colleagues in Grade Groups,thefinal ver-sion that reflected the input of all teachers was adopted with the aim of setting quality standards for materials to be produced for the bank (Appendix A).This module was completed in5 weeks.4.2.3.2.Module2:Establishing a classification, borrowing,maintenance,and evaluation system for the bank After the characteristics of effective materials were identified at the end of Module1, Modules2and3were carried out simultaneously. The system for classification,borrowing,mainte-nance,and evaluation of the materials in the bank was agreed upon with the input of all teach-ers who were going to use the bank.To achieve a consensus,the three groups mentioned above were involved in all stages of the negotiation pro-cess over a time period of two months,enabling each teacher to express views.The following were adopted as the main guid-ing principles:.For each material that will be placed in the bank,the material designer will complete a cover form that includes the following infor-mation:˚Grade for which this material is designed˚Language proficiency of the group for which the material is designed˚Skill the material aims to improve(reading, writing,speaking,listening,research,studyskills,etc.)˚Structural and/or vocabulary focus of the material(e.g.tenses,conditionals,relativeclauses,lexical sets,etc.)˚Category of material(project,drama,arts/ crafts,game,etc.)683A.Daloglu/International Journal of Educational Development24(2004)677–690˚Teaching objective the material aims to ach-ieve˚Required background language,if any˚Required aids and materials(reference to accompanying charts or posters,stationaryneeded,etc.)˚Name of the material designer.Both a hard copy and an electronic version of the materials will be included in the bank..For ease of access,materials will also be col-our-coded based on grade..All borrowers willfill in a feedback form(a hard copy or on the Internet)after using the material..Core group members will periodically share the feedback from material borrowers with the material designer who developed the material in question.The material designer will update the material,taking the feedback into consider-ation.4.2.3.3.Module3:Developing and piloting materi-als Material development and piloting took place in Grade Groups under the guidance of the exter-nal specialist and Core Group members who each were a leader of a Grade Group.Each Grade Group set targets and designed an action plan for materials production.When setting their specific targets,the groups considered the curricular objectives they were to cover over a period of two months and identified the discrepancies between the materials already available to them and the specific needs of their learners.As a result of this analysis,each group decided on the specific objec-tive the material would foster in the learners,the quantity of materials to be produced,and a realistic timeframe to produce them.A consider-able amount of materials were produced and piloted by the end of thefirst semester.Piloting involved trying out the materials with a representative group of teachers and students before they were made available for wider use with the aim of identifying and remedying prob-lems and faults.As Davidson summarizes,‘‘in general,piloting provides a feel for whether the material actually works or not;whether the aims of the material are fulfilled;whether it’s appropri-ate in level,content,and approach;whether it relates well to teachers’expectations and stages of development;whether it successfully promotes learning(Davidson,1998,p.184).Therefore,the piloting stage sought answers to the following questions:.Is the material comprehensible to the teacher and the learners?.Are the instructions clear?.Is the pacing of the material appropriate?.Does the material address learners’needs?.Is there sufficient amount of practice material? .Does the material interest and engage the learners?In the piloting process,teacher feedback was sought through a questionnaire designed for this purpose and student feedback was obtained directly by asking a random sample of students in the classes where these materials were piloted and indirectly by asking the teachers about their stu-dents’participation in the lessons and their reac-tions to these materials.Direct student feedback was obtained through mini-talks with younger students(grades1–3)and through mini-ques-tionnaires with older students(grades4and5). Then,the materials were revised in the light of the teacher and student feedback.During the second semester,materials pro-duction continued.After the accumulation of suf-ficient quantity of materials towards the end of the academic year,the materials bank was open to use by all of the teachers.5.Exploring the effectiveness of the program Exploration of the effectiveness of the pro-fessional development program was the next step. The effectiveness study was guided by the follow-ing questions:1.What are teachers’opinions on the usefulnessof the in-service professional development pro-gram?2.What changes do the teachers see in them-selves as a result of participating in the pro-A.Daloglu/International Journal of Educational Development24(2004)677–690 684。

指标组别序号前次测分后次测分样本量寻求真相干预组13451前次测分54寻求真相干预组23136后次测分54寻求真相干预组32937寻求真相干预组43648寻求真相干预组52950寻求真相干预组64144寻求真相干预组73937寻求真相干预组83248寻求真相干预组93448寻求真相干预组104049寻求真相干预组112346寻求真相干预组123035寻求真相干预组134152寻求真相干预组144142寻求真相干预组153842寻求真相干预组163438寻求真相干预组173638寻求真相干预组183241寻求真相干预组194133寻求真相干预组203145寻求真相干预组213645寻求真相干预组223449寻求真相干预组234046寻求真相干预组243046寻求真相干预组253248寻求真相干预组264453寻求真相干预组274254寻求真相干预组282247寻求真相干预组292940寻求真相干预组302643寻求真相干预组313232寻求真相干预组323037寻求真相干预组334056寻求真相干预组343640寻求真相干预组353543寻求真相干预组363437寻求真相干预组373846寻求真相干预组383839寻求真相干预组393540寻求真相干预组403840寻求真相干预组413743寻求真相干预组424441寻求真相干预组433838寻求真相干预组444134寻求真相干预组453641寻求真相干预组462943寻求真相干预组472445寻求真相干预组483645寻求真相干预组493139寻求真相干预组502344寻求真相干预组513833寻求真相干预组523145寻求真相干预组533154寻求真相干预组543847样本量寻求真相对照组14429前次测分54寻求真相对照组24126后次测分54寻求真相对照组32626寻求真相对照组44536寻求真相对照组54123寻求真相对照组62739寻求真相对照组74649寻求真相对照组82817寻求真相对照组92643寻求真相对照组103826寻求真相对照组113032寻求真相对照组124135寻求真相对照组133738寻求真相对照组143942寻求真相对照组152747寻求真相对照组162942寻求真相对照组173346寻求真相对照组182751寻求真相对照组194644寻求真相对照组202848寻求真相对照组214539寻求真相对照组224446寻求真相对照组233147寻求真相对照组244148寻求真相对照组253760寻求真相对照组265148寻求真相对照组273540寻求真相对照组284345寻求真相对照组292347寻求真相对照组302949寻求真相对照组312931寻求真相对照组323846寻求真相对照组333541寻求真相对照组344040寻求真相对照组353046寻求真相对照组363137寻求真相对照组373643寻求真相对照组384138寻求真相对照组393441寻求真相对照组403540寻求真相对照组413038寻求真相对照组424443寻求真相对照组432928寻求真相对照组444845寻求真相对照组453930寻求真相对照组463535寻求真相对照组473330寻求真相对照组483632寻求真相对照组493037寻求真相对照组503733寻求真相对照组512039寻求真相对照组523638寻求真相对照组534532寻求真相对照组544828样本量开放思想干预组13646前次测分54开放思想干预组24844后次测分54开放思想干预组33445开放思想干预组43446开放思想干预组53846开放思想干预组64245开放思想干预组74645开放思想干预组83346开放思想干预组93444开放思想干预组104347开放思想干预组112950开放思想干预组123742开放思想干预组134452开放思想干预组144148开放思想干预组153645开放思想干预组164048开放思想干预组174046开放思想干预组183741开放思想干预组194446开放思想干预组204445开放思想干预组213952开放思想干预组224057开放思想干预组233848开放思想干预组242740开放思想干预组253353开放思想干预组263741开放思想干预组273549开放思想干预组283442开放思想干预组293253开放思想干预组303843开放思想干预组314146开放思想干预组323449开放思想干预组333858开放思想干预组344052开放思想干预组353949开放思想干预组363942开放思想干预组373947开放思想干预组383744开放思想干预组393541开放思想干预组403844开放思想干预组414048开放思想干预组423748开放思想干预组434038开放思想干预组443638开放思想干预组453540开放思想干预组463944开放思想干预组473045开放思想干预组483348开放思想干预组493744开放思想干预组503143开放思想干预组513337开放思想干预组523344开放思想干预组533649开放思想干预组543253样本量开放思想对照组14628前次测分54开放思想对照组24038后次测分54开放思想对照组34027开放思想对照组44337开放思想对照组55128开放思想对照组63020开放思想对照组74048开放思想对照组82633开放思想对照组93247开放思想对照组104350开放思想对照组113151开放思想对照组123938开放思想对照组134447开放思想对照组143540开放思想对照组153951开放思想对照组164338开放思想对照组174347开放思想对照组184246开放思想对照组194743开放思想对照组204153开放思想对照组214054开放思想对照组224150开放思想对照组233248开放思想对照组244349开放思想对照组253853开放思想对照组265649开放思想对照组274050开放思想对照组284944开放思想对照组293752开放思想对照组303848开放思想对照组313448开放思想对照组324055开放思想对照组333441开放思想对照组344946开放思想对照组354250开放思想对照组364143开放思想对照组373746开放思想对照组383934开放思想对照组394645开放思想对照组403834开放思想对照组414243开放思想对照组424341开放思想对照组434034开放思想对照组444640开放思想对照组453735开放思想对照组463333开放思想对照组473035开放思想对照组484228开放思想对照组492530开放思想对照组504137开放思想对照组513738开放思想对照组524242开放思想对照组533935开放思想对照组543222样本量分析能力干预组14550前次测分54分析能力干预组24241后次测分54分析能力干预组33539分析能力干预组44044分析能力干预组54046分析能力干预组64547分析能力干预组74141分析能力干预组84455分析能力干预组93241分析能力干预组104248分析能力干预组112548分析能力干预组124448分析能力干预组134256分析能力干预组143648分析能力干预组154241分析能力干预组164556分析能力干预组173949分析能力干预组183940分析能力干预组194144分析能力干预组203748分析能力干预组213656分析能力干预组223946分析能力干预组234045分析能力干预组243539分析能力干预组253750分析能力干预组263751分析能力干预组273944分析能力干预组283646分析能力干预组294353分析能力干预组303548分析能力干预组313847分析能力干预组324349分析能力干预组332849分析能力干预组344353分析能力干预组354142分析能力干预组364042分析能力干预组373845分析能力干预组384045分析能力干预组393944分析能力干预组403944分析能力干预组413943分析能力干预组423847分析能力干预组434350分析能力干预组443353分析能力干预组453242分析能力干预组464448分析能力干预组473439分析能力干预组484444分析能力干预组494038分析能力干预组503951分析能力干预组513037分析能力干预组522747分析能力干预组533345分析能力干预组543151样本量分析能力对照组14346前次测分54分析能力对照组25041后次测分54分析能力对照组34038分析能力对照组44338分析能力对照组54539分析能力对照组63439分析能力对照组85341分析能力对照组94746分析能力对照组103550分析能力对照组113538分析能力对照组124739分析能力对照组134244分析能力对照组144341分析能力对照组154145分析能力对照组164444分析能力对照组174551分析能力对照组184949分析能力对照组194446分析能力对照组204752分析能力对照组214245分析能力对照组224343分析能力对照组233648分析能力对照组244649分析能力对照组254353分析能力对照组264352分析能力对照组273850分析能力对照组284149分析能力对照组295045分析能力对照组303651分析能力对照组312844分析能力对照组324350分析能力对照组333944分析能力对照组344844分析能力对照组354046分析能力对照组363049分析能力对照组374746分析能力对照组383640分析能力对照组394041分析能力对照组404152分析能力对照组413848分析能力对照组423637分析能力对照组433935分析能力对照组443733分析能力对照组454242分析能力对照组464337分析能力对照组473737分析能力对照组483733分析能力对照组493638分析能力对照组503041分析能力对照组514245分析能力对照组524642分析能力对照组534749样本量系统化能力干预组13749前次测分54系统化能力干预组22442后次测分54系统化能力干预组32644系统化能力干预组43547系统化能力干预组53742系统化能力干预组63844系统化能力干预组74648系统化能力干预组84046系统化能力干预组93541系统化能力干预组103846系统化能力干预组112241系统化能力干预组123239系统化能力干预组134460系统化能力干预组144252系统化能力干预组153737系统化能力干预组164234系统化能力干预组173246系统化能力干预组183945系统化能力干预组193935系统化能力干预组203343系统化能力干预组214350系统化能力干预组223152系统化能力干预组233948系统化能力干预组242838系统化能力干预组253250系统化能力干预组263649系统化能力干预组273451系统化能力干预组282550系统化能力干预组293443系统化能力干预组303145系统化能力干预组313436系统化能力干预组323637系统化能力干预组334054系统化能力干预组343835系统化能力干预组354039系统化能力干预组364038系统化能力干预组373143系统化能力干预组384033系统化能力干预组393950系统化能力干预组404140系统化能力干预组414152系统化能力干预组423942系统化能力干预组434149系统化能力干预组443646系统化能力干预组453444系统化能力干预组463642系统化能力干预组473845系统化能力干预组483934系统化能力干预组493732系统化能力干预组503838系统化能力干预组514348系统化能力干预组522847系统化能力干预组533041系统化能力干预组542749样本量系统化能力对照组14951前次测分54系统化能力对照组24333后次测分54系统化能力对照组32829系统化能力对照组44836系统化能力对照组54616系统化能力对照组63123系统化能力对照组73946系统化能力对照组82430系统化能力对照组94151系统化能力对照组103245系统化能力对照组112427系统化能力对照组124125系统化能力对照组134032系统化能力对照组144031系统化能力对照组153348系统化能力对照组163541系统化能力对照组173642系统化能力对照组182250系统化能力对照组193643系统化能力对照组203546系统化能力对照组213742系统化能力对照组223937系统化能力对照组232738系统化能力对照组243547系统化能力对照组253648系统化能力对照组264647系统化能力对照组272748系统化能力对照组285248系统化能力对照组292544系统化能力对照组303654系统化能力对照组313043系统化能力对照组323352系统化能力对照组333543系统化能力对照组344338系统化能力对照组352751系统化能力对照组363840系统化能力对照组373845系统化能力对照组382834系统化能力对照组393533系统化能力对照组404147系统化能力对照组413739系统化能力对照组423049系统化能力对照组432739系统化能力对照组444742系统化能力对照组453641系统化能力对照组464634系统化能力对照组474339系统化能力对照组484229系统化能力对照组493134系统化能力对照组503335系统化能力对照组513725系统化能力对照组523932系统化能力对照组534242系统化能力对照组543433样本量批判思维干预组14448前次测分54批判思维干预组24545后次测分54批判思维干预组33644批判思维干预组44142批判思维干预组54141批判思维干预组63742批判思维干预组74343批判思维干预组83545批判思维干预组93444批判思维干预组104348批判思维干预组112940批判思维干预组123553批判思维干预组134244批判思维干预组143650批判思维干预组153541批判思维干预组163654批判思维干预组174344批判思维干预组184346批判思维干预组193842批判思维干预组203441批判思维干预组213144批判思维干预组224552批判思维干预组233349批判思维干预组243232批判思维干预组253346批判思维干预组263243批判思维干预组273840批判思维干预组283248批判思维干预组293545批判思维干预组302843批判思维干预组314445批判思维干预组323443批判思维干预组333953批判思维干预组343946批判思维干预组353943批判思维干预组364140批判思维干预组372645批判思维干预组383536批判思维干预组393846批判思维干预组403651批判思维干预组413453批判思维干预组422943批判思维干预组433751批判思维干预组442640批判思维干预组453243批判思维干预组463947批判思维干预组474339批判思维干预组484226批判思维干预组493030批判思维干预组503843批判思维干预组514044批判思维干预组523140批判思维干预组534240批判思维干预组542251样本量批判思维对照组14850前次测分54批判思维对照组24246后次测分54批判思维对照组34751批判思维对照组44250批判思维对照组54045批判思维对照组64947批判思维对照组75047批判思维对照组84050批判思维对照组92241批判思维对照组104649批判思维对照组114150批判思维对照组124146批判思维对照组134757批判思维对照组144354批判思维对照组154444批判思维对照组164556批判思维对照组174249批判思维对照组184443批判思维对照组194251批判思维对照组204149批判思维对照组214253批判思维对照组224453批判思维对照组234053批判思维对照组243538批判思维对照组253641批判思维对照组263949批判思维对照组274355批判思维对照组283649批判思维对照组293554批判思维对照组303451批判思维对照组314248批判思维对照组324445批判思维对照组333650批判思维对照组344454批判思维对照组354049批判思维对照组364237批判思维对照组373447批判思维对照组384242批判思维对照组394150批判思维对照组404141批判思维对照组414457批判思维对照组424450批判思维对照组434644批判思维对照组443052批判思维对照组453442批判思维对照组463951批判思维对照组473247批判思维对照组484340批判思维对照组494039批判思维对照组504351批判思维对照组512946批判思维对照组524452批判思维对照组534044批判思维对照组543856样本量求知欲干预组13923前次测分54求知欲干预组25148后次测分54求知欲干预组34134求知欲干预组44442求知欲干预组54339求知欲干预组63343求知欲干预组73529求知欲干预组84231求知欲干预组93538求知欲干预组103833求知欲干预组113238求知欲干预组123234求知欲干预组134443求知欲干预组144246求知欲干预组154347求知欲干预组164647求知欲干预组174237求知欲干预组184243求知欲干预组193244求知欲干预组203545求知欲干预组213841求知欲干预组222842求知欲干预组233643求知欲干预组243746求知欲干预组254454求知欲干预组263545求知欲干预组273142求知欲干预组284642求知欲干预组293140求知欲干预组303251求知欲干预组313347求知欲干预组323852求知欲干预组333940求知欲干预组343933求知欲干预组353536求知欲干预组363644求知欲干预组374043求知欲干预组383944求知欲干预组393733求知欲干预组404154求知欲干预组413041求知欲干预组424434求知欲干预组433935求知欲干预组444731求知欲干预组453740求知欲干预组463824求知欲干预组474026求知欲干预组483735求知欲干预组493330求知欲干预组503135求知欲干预组513229求知欲干预组524138求知欲干预组534236求知欲干预组543640样本量求知欲对照组14832前次测分54求知欲对照组25447后次测分54求知欲对照组35042求知欲对照组44641求知欲对照组55023求知欲对照组74446求知欲对照组84626求知欲对照组94744求知欲对照组104054求知欲对照组113847求知欲对照组125537求知欲对照组134950求知欲对照组144445求知欲对照组154448求知欲对照组164639求知欲对照组174645求知欲对照组184351求知欲对照组194147求知欲对照组204351求知欲对照组214148求知欲对照组224640求知欲对照组233949求知欲对照组244647求知欲对照组253448求知欲对照组264950求知欲对照组273648求知欲对照组284054求知欲对照组293847求知欲对照组304746求知欲对照组313836求知欲对照组323954求知欲对照组333836求知欲对照组344543求知欲对照组354645求知欲对照组362648求知欲对照组374548求知欲对照组383845求知欲对照组394840求知欲对照组404249求知欲对照组414149求知欲对照组425238求知欲对照组434243求知欲对照组443948求知欲对照组454440求知欲对照组463333求知欲对照组473533求知欲对照组484637求知欲对照组492541求知欲对照组503040求知欲对照组512539求知欲对照组524648求知欲对照组544524样本量认知成熟干预组13751前次测分54认知成熟干预组23739后次测分54认知成熟干预组32246认知成熟干预组42851认知成熟干预组53848认知成熟干预组64354认知成熟干预组73547认知成熟干预组82647认知成熟干预组93239认知成熟干预组103554认知成熟干预组112545认知成熟干预组123048认知成熟干预组133448认知成熟干预组143651认知成熟干预组154451认知成熟干预组164244认知成熟干预组173949认知成熟干预组184343认知成熟干预组193640认知成熟干预组203256认知成熟干预组213348认知成熟干预组223450认知成熟干预组233741认知成熟干预组243549认知成熟干预组253650认知成熟干预组264346认知成熟干预组273946认知成熟干预组283745认知成熟干预组293049认知成熟干预组303345认知成熟干预组313050认知成熟干预组323648认知成熟干预组334147认知成熟干预组343549认知成熟干预组353841认知成熟干预组363946认知成熟干预组374347认知成熟干预组384151认知成熟干预组393546认知成熟干预组404634认知成熟干预组413553认知成熟干预组424347认知成熟干预组433445认知成熟干预组443642认知成熟干预组453437认知成熟干预组464050认知成熟干预组472942认知成熟干预组483751认知成熟干预组494048认知成熟干预组503245认知成熟干预组513937认知成熟干预组524547认知成熟干预组533653认知成熟干预组543554样本量认知成熟对照组14148前次测分54认知成熟对照组24728后次测分54认知成熟对照组33533认知成熟对照组44617认知成熟对照组54024认知成熟对照组63532认知成熟对照组73854认知成熟对照组83731认知成熟对照组93851认知成熟对照组105136认知成熟对照组113738认知成熟对照组123836认知成熟对照组134437认知成熟对照组144442认知成熟对照组154352认知成熟对照组163737认知成熟对照组173341认知成熟对照组184254认知成熟对照组194546认知成熟对照组204549认知成熟对照组213945认知成熟对照组225143认知成熟对照组234142认知成熟对照组243545认知成熟对照组253850认知成熟对照组263951认知成熟对照组274444认知成熟对照组284646认知成熟对照组293350认知成熟对照组303654认知成熟对照组314435认知成熟对照组323949认知成熟对照组333139认知成熟对照组343636认知成熟对照组355041认知成熟对照组362942认知成熟对照组374038认知成熟对照组383648认知成熟对照组394637认知成熟对照组403443认知成熟对照组413337认知成熟对照组423249认知成熟对照组433532认知成熟对照组443740认知成熟对照组453143认知成熟对照组464231认知成熟对照组473849认知成熟对照组483341认知成熟对照组493042认知成熟对照组503536认知成熟对照组514041认知成熟对照组523241认知成熟对照组534843认知成熟对照组543545偏度系数(Skewness)偏度系数标准误z值P值-0.412705850.324556264-1.2716003210.2035151630.1155251590.3245562640.3559480170.721879495偏度系数(Skewness)偏度系数标准误z值P值0.0352889320.3245562640.1087297830.913416819-0.277638530.324556264-0.8554403680.392307404偏度系数(Skewness)偏度系数标准误z值P值0.1493056270.3245562640.4600300280.6454946670.4359302970.324556264 1.3431578610.179220863偏度系数(Skewness)偏度系数标准误z值P值-0.0914984290.324556264-0.2819185440.77800597-0.5457332480.324556264-1.6814750120.092670686偏度系数(Skewness)偏度系数标准误z值P值-0.8413843660.324556264-2.5924145030.0095304870.1644553820.3245562640.506708390.612359443偏度系数(Skewness)偏度系数标准误z值P值-0.2430438410.324556264-0.7488496390.453947837-0.1647865580.324556264-0.5077287850.611643559偏度系数(Skewness)偏度系数标准误z值P值-0.6718159910.324556264-2.0699523170.038456810.0323786060.3245562640.099762690.920532729偏度系数(Skewness)偏度系数标准误z值P值0.0303071850.3245562640.0933803740.925601382-0.5142681110.324556264-1.584526840.113073879偏度系数(Skewness)偏度系数标准误z值P值-0.3945365010.324556264-1.2156181990.224130398-0.7401695840.324556264-2.2805586160.022574579偏度系数(Skewness)偏度系数标准误z值P值-1.1279582890.324556264-3.4753859770.000510119-0.3483441270.324556264-1.0732934960.283139452偏度系数(Skewness)偏度系数标准误z值P值0.1978663150.3245562640.6096518130.542092481-0.1841407510.324556264-0.567361570.570468554偏度系数(Skewness)偏度系数标准误z值P值-0.7828427610.324556264-2.4120402140.015863532-1.023*******.324556264-3.154992160.001605024偏度系数(Skewness)偏度系数标准误z值P值-0.3886817680.324556264-1.1975790060.231080953-0.5928268790.324556264-1.8265766050.067763454偏度系数(Skewness)偏度系数标准误z值P值0.385252890.324556264 1.1870141870.235222025-0.6347244510.324556264-1.9556684670.050504222峰度系数(Kurtosis)峰度系数标准误z值P值结论-0.3029660520.638893069-0.474204630.635353992符合正态分布-0.3511440150.638893069-0.5496131230.582584756符合正态分布峰度系数(Kurtosis)峰度系数标准误z值P值结论-0.8064595470.638893069-1.262276250.2068494符合正态分布-0.7633656560.638893069-1.1948253830.232155261符合正态分布峰度系数(Kurtosis)峰度系数标准误z值P值结论0.1571070060.6388930690.2459050090.805755766符合正态分布0.1035251390.6388930690.1620382880.871275703符合正态分布峰度系数(Kurtosis)峰度系数标准误z值P值结论0.7277737780.638893069 1.1391167210.254654474符合正态分布0.7992990030.638893069 1.2510685140.210909482符合正态分布峰度系数(Kurtosis)峰度系数标准误z值P值结论0.3922118530.6388930690.6138927960.539286171不符合正态分布0.4201716530.6388930690.6576556760.51075941符合正态分布峰度系数(Kurtosis)峰度系数标准误z值P值结论0.014475860.6388930690.022657720.981923302符合正态分布-0.0351346240.638893069-0.0549929650.956144068符合正态分布峰度系数(Kurtosis)峰度系数标准误z值P值结论0.023*******.6388930690.0372309230.970300883不符合正态分布-0.0392462710.638893069-0.0614285430.951017921符合正态分布峰度系数(Kurtosis)峰度系数标准误z值P值结论-0.4709360410.638893069-0.7371124590.461053963符合正态分布-0.4143251160.638893069-0.6485046340.516658615符合正态分布峰度系数(Kurtosis)峰度系数标准误z值P值结论-0.2674217650.638893069-0.4185704590.675530083符合正态分布-0.2262126830.638893069-0.354069710.723286642不符合正态分布峰度系数(Kurtosis)峰度系数标准误z值P值结论2.1571047340.6388930693.3763157530.000734636不符合正态分布2.2636640460.6388930693.543103150.000395448不符合正态分布峰度系数(Kurtosis)峰度系数标准误z值P值结论-0.4030232570.638893069-0.6308148840.52816157符合正态分布-0.4457666490.638893069-0.6977171460.485354103符合正态分布峰度系数(Kurtosis)峰度系数标准误z值P值结论0.8984794460.638893069 1.4063064530.159633145不符合正态分布0.8806224570.638893069 1.3783565660.168093226不符合正态分布峰度系数(Kurtosis)峰度系数标准误z值P值结论0.283849760.6388930690.4442836740.656837504符合正态分布0.2209716390.6388930690.3458663890.729443129符合正态分布峰度系数(Kurtosis)峰度系数标准误z值P值结论-0.5842541080.638893069-0.9144787080.360465361符合正态分布-0.6067254490.638893069-0.9496510120.342289609符合正态分布。

Automatic Ranking of Clones for Refactoring through Mining Association RulesManishankar Mondal Chanchal K.Roy Kevin A.SchneiderDepartment of Computer Science,University of Saskatchewan,Canada{mshankar.mondal,chanchal.roy,kevin.schneider}@usask.caAbstract—In this paper,we present an in-depth empirical study on identifying clone fragments that can be important refactoring candidates.We mine association rules among clones in order to detect clone fragments that belong to the same clone class and have a tendency of changing together during software evolution. The idea is that if two or more clone fragments from the same class often change together(i.e.,are likely to co-change) preserving their similarity,they might be important candidates for refactoring.Merging such clones into one(if possible)can potentially decrease future clone maintenance effort.We define a particular clone change pattern,the Similarity Preserving Change Pattern(SPCP),and consider the cloned fragments that changed according to this pattern(i.e.,the SPCP clones)as important candidates for refactoring.For the purpose of our study,we implement a prototype tool called MARC that identifies SPCP clones and mines association rules among these.The rules as well as the SPCP clones are ranked for refactoring on the basis of their change-proneness.We applied MARC on thirteen subject systems and retrieved the refactoring candidates for three types of clones(Type1,Type2,and Type3) separately.Our experimental results show that SPCP clones can be considered important candidates for refactoring.Clones that do not follow SPCP either evolve independently or are rarely changed.By considering SPCP clones for refactoring we not only can minimize refactoring effort considerably but also can reduce the possibility of delayed synchronizations among clones and thus,can minimize inconsistencies in software systems.Keywords-Clone Change Pattern;Association Rule;Clone Class;Clone Refactoring;I.I NTRODUCTIONCode cloning is a common yet controversial practice fre-quently employed by programmers during both development and maintenance of software systems.Cloning involves copy-ing a code fragment from one place and pasting it in one or more additional places in the code-base with or without modifications causing the same or similar code fragments to be scattered throughout the system.The original code fragment (i.e.,the code fragment from which the copies were created) and the pasted code fragments are clones of one another. Numerous empirical studies[8],[10],[13],[14],[15],[24] have been conducted identifying the possible impact of clones on software maintenance.While a number of studies[13],[14], [8]reported that clones are beneficial to both software devel-opment and maintenance,there is strong empirical evidence [15],[10]of the negative effects of clones,including hidden bug propagation and unintentional inconsistent changes.Also, higher number of clones indicate higher change-proneness of the software systems[18]as well as higher maintenance effort and cost.The negative effects of clones indicatetheFig.1.Change history of clone fragmentsnecessity of clone refactoring.Clone refactoring refers to the task of merging several clone fragments(that are similar to one another)into a single one(if possible).Motivation.A number of clone refactoring techniques[2], [11],[22],[29],[7],[23]have been proposed by different studies.Before refactoring,it is important to identify the clones that are our primary refactoring candidates because, there can be a large number of clones in a system and not all of them need to be refactored[12].That is,we should identify clones that would be important to refactor.Clone refactoring may not be able to be fully automated as it may require critical analysis by the programmer.Thus,a significant amount of effort and cost might sometimes need to be spent for refactoring clones.Identifying and ranking clones according to refactoring need can help us minimize refactoring effort and cost,because we are able to focus on just those clones that are important to be refactored,and we can leave the clones where refactoring is less important or unnecessary.However,there is no existing study that focuses on how we should identify and rank the important clones(from the whole set of clones in a code-base)for refactoring.Zibran and Roy[29]proposed an optimal scheduling algorithm for clone refactoring considering all the clones in the code-base.In our study,we propose to identify only important clones for refactoring based on their clone evolution history.The scheduling algorithm[29]can then be applied only on these important clones keeping the rest out of the desk.According to our consideration,all clones in a software system might not need to be refactored with equal importance. We use the clone change example presented in Fig.1to explain this.We see that there are nine code fragments formingfour groups(CG-1through CG-4).The code fragments in a particular group are clones of one another.The change history (in Fig.1)of these code fragments implies the followings. (1)The clone fragments,CF-1and CF-2in group CG-1,are likely to be related to each other and they have received corresponding changes.In other words,it is likely that the changes were made to these clones focusing on their consistency.The same is also true for the two code fragments CF-6and CF-7in CG-3.(2)It is likely that the clone fragments,CF-3and CF-4in group CG-2,have experienced independent evolution.Because of the independent evolutions,CF-3and CF-4might not be regarded as clones of each other after a particular evolution period.Out of the three clone fragments in group CG-3,clone fragments CF-6and CF-7seem to be related as they received corresponding changes.However,the other clone fragment CF-5seems to have a tendency of independent evolution. (3)The clone fragments,CF-8and CF-9,are not change-prone and it is likely that in future they will exhibit lower change-proneness compared to the others.Thus,these clones are not likely to add change effort during maintenance.The example in Fig.1implies that refactoring clone frag-ments might not always be appropriate,since clones might evolve independently without preserving similarity.Also,if some clone fragments do not change during evolution we might not consider refactoring those clone fragments,since they do not require additional change effort during software evolution.Thus,when clone fragments belonging to the same clone class change consistently during evolution these clone fragments might be important refactoring candidates.More-over,a clone class may contain n clone fragments,however,if it is observed that only a subset of the clone fragments change consistently while others are either evolving independently or are rarely changing we should consider refactoring only those consistently changing clone fragments.If the consistently changing clones can be merged through refactoring we can reduce the effort spent for changing clones.The co-change histories of the clones:(1)CF-1and CF-2in CG-1,and(2) CF-6and CF-7in CG-3indicate that such clone fragments can be identified by mining association rules among clones. Contribution.Focusing on the above discussion we define a particular clone change pattern called SPCP(Similarity Preserving Change Pattern)such that the clone fragments that change following this pattern(i.e.,SPCP clones)are likely to be important candidates for refactoring.We describe SPCP in Section IV.For the purpose of our study,we develop a prototype tool MARC(Mining Association Rules among Clones)that can detect all SPCP clones from a subject system and then mines association rules among SPCP clones.MARC ranks these rules according to their support and confidence values(defined in Section III).According to our investigation on the rules as well as SPCP clones retrieved by MARC, (1)SPCP clones can be important candidates for refac-toring.The clones that do not follow SPCP either evolve independently or are rarely changed during evolution.Thus, we can mainly focus on the SPCP clones forrefactoring.Fig.2.Proposed refactoring step(2)Overall,only7.04%of the clones existing in a code-base are SPCP clones.Also,for each of63.44%of the association rules retrieved by MARC,the corresponding SPCP clones are method clones and also,they belong to the same source codefile.Thus,automatic identification and ranking of SPCP clones can save a considerable amount of time,effort and cost for clone refactoring,because we could leave the remaining 92.96%of the clones in the code-base without refactoring.(3)From our manual analysis on224association rules from all13subject systems(considering the top10rules of each clone-type),for overall64.37%of the association rules we can suggest a standard refactoring technique1.(4)A considerable amount(overall11.64%)of SPCP clones can receive resynchronizing changes.Thus,refactoring of SPCP clones can minimize delayed synchronizations among clone fragments and can minimize unwanted inconsistencies in software systems.The rest of the paper is organized as follows:Section II describes the significance of our study,Section III describes the terminology,Section IV elaborates on the SPCP(similarity preserving change pattern),Section V presents experimental results and discussion,Section VI mentions some threats to validity,Section VII discusses related work,and Section VIII concludes the paper mentioning future work.II.S IGNIFICANCE OF OUR STUDYExisting clone refactoring studies and techniques mainly consider four refactoring steps(cf.Fig.2):(1)detection of clones,(2)scheduling of clones for refactoring(3)analysis of refactoring possibilities on the basis of different cloning situations,and(4)application of selected refactoring.Our study differs in that we propose an additional step after clone detection that involves the analysis of the clone evolution history to determine the clones we should consider as the primary refactoring candidates.According to our expectation, this additional step will minimize the clone refactoring effort and task considerably,because this stepfilters out a significant portion of clones from the refactoring target list based on their change pattern and change-proneness.According to our analysis the excluded clones do not need to be refactored with the same importance as the ones included in the target list, since they either changed rarely or changed independently.III.T ERMINOLOGYTypes of Clones.We conducted our experiment considering exact(Type1)and near-miss clones(Type2and Type3 1Refactoring Techniques:/catalog/clones).If two code fragments are exactly the same disregard-ing comments and indentations,they are Type1clones of each other.Type2clones are syntactically similar code fragments. In general,Type2clones are created from Type1clones because of renaming variables or changing data types.Type3 clones are mainly created because of additions,deletions,or modifications of lines in Type1or Type2clones.Clone Class.A group(i.e.,two or more)of clone fragments that are the same(Type1)or similar(Type2or Type3)to one another form a clone class.Cloned Method.If a method contains cloned(Type1,Type 2,or Type3)lines,we call this method a cloned method.If all lines of a method are cloned lines,then this method is a fully cloned method.If a method contains both cloned and non-cloned lines,we call this method a partially cloned method. Method Clones.If two or more methods are clones(Type 1,Type2,or Type3)of one another,we refer to these as method clones.Method clones are fully cloned methods. Association Rule.An association rule[1]is an expression of the form X=>Y where X is the antecedent and Y is the consequent.Each of X and Y is a set of one or more program entities.The meaning of such a rule in our context is that if X gets changed in a particular commit operation,Y also has the tendency of getting changed in that commit operation.We can determine the confidence or strength of a particular association rule by determining the support of its constituent parts. Support and Confidence.Support is the number of commit operations in which an entity or a group(two or more) of entities changed together.We consider an example of two entities E1and E2.If E1and E2have ever changed together,we can assume two association rules,E1=>E2 and E2=>E1,from them.Suppose,E1changed in four commits:2,5,6,and10.E2changed in six commits:4,6, 7,8,10,and13.Thus,support(E1)=4and support(E2)=6. However,support(E1,E2)=2,because E1and E2changed together in two commits:6,and10.Also,support(E1=>E2) =support(E2=>E1)=support(E1,E2)=2.Confidence of an association rule,X=>Y,determines the probability that Y will change in a commit operation provided that X changed in that commit operation.We determine the confidence of X=>Y in the following way.confidence(X=>Y)=support(X,Y) support(X)(1) From the above example of two entities,confidence(E1=>E2)=support(E1,E2)/support(E1)=2/4=0.5and confidence(E2=>E1)=2/6=0.33.In our experiment we consider those association rules where each of X and Y consist of a single clone fragment from the same clone class. Such a rule can be expressed as x=>y where x and y are two different clone fragments belonging to the same clone class.IV.S IMILARITY P RESERVING C HANGE P ATTERNOur prototype tool,MARC,mines association rules con-sidering those clone fragments that followed a similarity preserving change pattern(SPCP)during evolution.It can also rank these rules on the basis of change-proneness(described in Section IV-D)of the participating clones.We define similarity preserving change pattern in the following way.A.Definition of Similarity Preserving Change PatternIf two clone blocks received either similarity preserving changes or re-synchronizing changes or both during evolu-tion,then we say that these clone blocks follow a similarity preserving change pattern(i.e.,are SPCP clones).Definition of Similarity Preserving Change.We consider two clone blocks CB1and CB2that belong to the same clone class,say CLS1,in revision R i.Suppose,a commit operation C i on R i changes any(one or both)of these clone fragments.If in revision R i+1(created because of commit C i) these two clone blocks,CB1and CB2,again remain in one particular clone class(which might not be CLS1),then we say that CB1and CB2have received a similarity preserving change in commit operation C i.If both of the clone blocks (i.e.,CB1and CB2)change preserving their similarity in such a commit then we call this change a similarity preserving co-change(SPCO).If the SPCP of two clone blocks contains SPCOs,then it is likely that the participating clone blocks have changed consistently(evaluated in Section V-A).Definition of Re-synchronizing Change.Suppose,two clone blocks CB1and CB2belong to the same clone class, CLS1,in revision R i.The commit C i on revision R i modified any of these clone blocks in such a way that CB1and CB2 could not be considered as clones of each other in revision R i+1(i.e.,CB1and CB2may diverge into two different clone classes or one or both of these might not be regarded as a clone fragment).However,in a later commit operation, say C i+n where n>=1,any one or both of CB1and CB2 changed in such a way that CB1and CB2become clones of each other(they converged into one clone class)again.Such a converging change followed by a diverging change is termed as a re-synchronizing change in our experiment.B.Example of a Similarity Preserving Change Pattern Fig.3contains an SPCP followed by the clone blocks,CB1 and CB2.As indicated in thefigure,these clone blocks belong to two methods M1and M2respectively.We see that in each of the commit operations,C2to C7,the clone blocks CB1 and CB2received similarity preserving change.In commit C1,none of the clone blocks were changed.We now consider the commit operation C2.Before this commit both of the clone blocks(CB1and CB2)belonged to the clone class CLS1.After this commit,the clone blocks belonged to CLS2.Although CLS1and CLS2are different clone classes,we see that before or after this commit operation both clone blocks belonged to a single clone class.Thus,CB1and CB2preserved their similarity after commit C2.In other words,CB1and CB2 received a similarity preserving change in commit C2.We also see that these two clone blocks received similarity preserving change s in each of the commits C3to C7.Moreover,the similarity preserving changes in commits C2,C5,C6,and C7,are SPCOs(similarity preserving co-changes).Finally, the changes in commits C8to C10can be considered as anFig.3.Similarity Preserving Change Pattern (SPCP)example of re-synchronizing change.Because of the change in C8,CB 2diverged into a different clone class,CLS5,and thus,CB 1and CB 2could not be considered as clones of each other.However,the change in commit C10is a converging change because,both of the clone blocks again converged into a single clone class after this commit.C.Mining Association Rules Considering SPCPIn this experiment,we consider clones residing in methods.Thus,both fully cloned and partially cloned methods have been investigated.For a particular subject system,we collect all of its revisions (mentioned in Table I),then extract the methods in each revision using CTAGS,and then deter-mine method genealogies following the technique proposed by Lozano and Wermelinger [15].We detect clones in each revision using NiCad [5]and then map the clones to the already detected methods of the corresponding revisions.As method genealogies are already detected,after clone mapping we can easily track the evolution of each clone fragment.Finally,we detect changes between every two consecutive revisions and map these changes to the methods as well as clones located inside the methods.For the details of these steps and NiCad setup we refer the readers to our earlier work [17].Extraction of Association Rules.After the preliminary steps we determine all possible pairs of clones.A possible pair of clones consists of two clone fragments CF 1and CF 2from the same clone class such that they together followed an SPCP during the evolution and are alive in the last revision.As we map clones to methods,CF 1and CF 2reside in methods.From such a clone pair we can determine two association rules:CF 1=>CF 2,and CF 2=>CF 1.According to the definition,these two rules have the same support value.However,their confidences can be different.We determine support by the number of similarity preserving co-changes (SPCOs)in the SPCP followed by the clone fragments in a rule.We extract all association rules with a minimum support of 1.D.Ranking of Association RulesAccording to our consideration and discussion in the in-troduction,if a rule detected by our prototype tool has a higher support value (i.e.,higher SPCO count)compared to the others,we should assume a higher priority for refactoringthe associated clone fragments.Our decision of ranking con-sidering the support value is reasonable from two perspectives.(1)Higher support value (i.e.,higher SPCO count)for a rule (consisting of two SPCP clone fragments)indicates a higher likelihood that the participating clone fragments have changed consistently during evolution.The underlying assumption is that in a similarity preserving co-change (i.e.,in a SPCO),the two participating SPCP clone fragments generally change consistently.We empirically evaluate this in Section V-A.Intuitively,if two clone fragments have a tendency of changing consistently,then changes in one fragment in a particular commit generally require corresponding changes to the other one in that commit.(2)Higher support value for a rule is an evidence that the corresponding SPCP clones have exhibited higher change-proneness (i.e.,changed in higher number of commits)during the past evolution compared to the other SPCP clones in other rules.Thus,considering the existing evolution history we rank the association rules according to the decreasing order of change-proneness of the corresponding SPCP clones.As it is difficult to be certain about the future change-proneness of the rules as well as SPCP clones,our decision of ranking relying on the past history is reasonable.We assume higher ranks for those rules as well as SPCP clones that exhibited higher change-proneness in the past.However,higher support might also be an indicator of higher change-proneness of the associated SPCP clones in future.We do not investigate this issue (i.e.,future change-proneness)in this research work.E.Finding Groups of Refactoring CandidatesEach rule consists of two SPCP clones.This is also possible that more than two clone fragments from the same class are preserving their similarity during evolution following a similarity preserving change pattern (SPCP).Thus,this is convenient to determine groups of refactoring candidates from these rules where a group contains two or more clones (from the same clone class)and all the clones in a group have evolved following a SPCP.Suppose two clone blocks,CB1and CB2,formed a rule because they followed a SPCP.If there is another rule consisting of the clone blocks CB2and CB3(CB2is common in these two rules),then we can form a group consisting of CB1,CB2,and CB3,because according to the conditions in Section IV-A these three clone blocks togetherFig.4.Rules of Type3clones sorted in decreasing order of support values followed a SPCP.Focusing on this fact,MARC determines groups of refactoring candidates.We term each group as a SPCP clone-class.In Table II we report the count of groups for each subject system considering each clone-type.F.Tool SupportWe have developed our prototype tool such that for a particular clone-type of a particular subject system,it generates two XMLfiles.Onefile contains the ranked rules and the other one contains the SPCP clone groups merging these rules. While each rule in thefirstfile contains only two SPCP clones,a group in the secondfile may contain more than two SPCP clones.For each SPCP clone(whether in a rule or in a group)we include the starting and ending line numbers of the clone fragment,the name of the method containing the clone fragment,and the starting and ending line numbers of this method considering the last(i.e.,the latest)revision so that we can easily trace the clone fragment for refactoring in the latest revision of the candidate software system.Our prototype tool is now available[16]with instructions on how to use it. The six XMLfiles containing the association rules and groups of three types of SPCP clones of our subject system Freecol are also available on-line[16].In order to assist in analyzing the evolution of SPCP clones,our tool also shows important information regarding the ranked rules including(i)the list of commits where the SPCOs occurred,(ii)whether the participating clone blocks are method clones,(iii)whether the clones belong to the same file,(iv)the support and confidence values,(v)thefile paths and starting and ending line numbers of the clone blocks and container methods in the revision where the last SPCO occurred.Such a ranking with all information regarding the SPCP clones is presented in Fig.4that shows the top two rules of total481rules retrieved for Type3case of Carol.V.E XPERIMENTAL R ESULTS AND D ISCUSSIONWe applied our prototype tool MARC on each of the thirteen subject systems listed in Table I and detected all SPCP clones and association rules&groups formed by these SPCP clones considering three clone-types(Type1,Type2, and Type3)separately.We manually examined the changes occurred to the SPCP clones.According to our observation, implementation of the changes(similarity preserving change s and resynchronizing change s)required proper analysis by the responsible programmers.The changes were not tool generatedTABLE ISUBJECT SYSTEMSSystem Domain LOC Revisions Javafreecol Game91,6261950jEdit Text Editor1,91,8044000Plandora Project Management94,07673Carol Game25,0921699OpenYMSG Yahoo Messenger15,553297 CCtags Code Def.Generator33,270774QMail Admin Mail Management4,054317GNUMakeUniprocAuto-build Systemfor C/C++Projects68,095863 C#MonoOSC Formats&Protocols14,883355 GreenShot Multimedia37,628999Python Pyevolve Artificial Intelligence8.809200 Ocemp Game57,098438Noora Development Tool14,862140 and thus,these were not just reformatting or code transforma-tions(e.g.,replacement of for loops by for-each loops).In the following subsections and also in Fig.6we have mentioned and explained such changes.By analyzing our experimental results we answer the followingfive research questions.RQ1.Can we minimize clone refactoring effort and cost by considering SPCP clones for refactoring?RQ2.Are the changes occurring to the clone fragments in SPCOs(similarity preserving co-changes)consistencyensuring changes?RQ3.Can SPCP clones be candidates for refactoring?RQ4.What are the characteristics of the clones that change following similarity preserving change pattern(SPCP)? RQ5.What ratio of the SPCP clones do receive resynchro-nizing changes?Statistics of the important refactoring candidates:Table II shows the statistics of the clone fragments that followed SPCP.We regard these cloned fragments as the important refactoring candidates.For each type of clones of a particular subject system we determine the followings considering all revisions:(1)Number of clone classes per revision(CC),(2) Number of clone fragments per revision(CF),(3)Number of SPCP clones that is,the number of clone fragments that followed similarity preserving change pattern during evolution (SCF),(4)Number of SPCP clone-classes(SCC),(5)The percentage of SPCP clones(PSCF),and(6)Number of association rules formed by the SPCP clones(CR).These six measures for each clone type are presented in Table II.Look-ing at the percentages(PSCF)of the cloned fragments that followed SPCP(i.e.,the important candidates for refactoring) we realize that the number of important refactoring candidates can be considerably smaller compared to the total number of clone fragments in a system.From Table II,for each clone type,we also determined the overall percentages of the SPCP clones(denoted by Overall-PSCF)considering all subject systems according to the following equation.Overall-PSCF T i=∑for all systems SCF T1∑for all systems CF T1(2) Here,T i(i=1,2,or3)denotes a particular clone-type (Type1,Type2,or Type3),SCF T i denotes the numberTABLE IIS TATISTICS REGARDING THE IMPORTANT CLONED FRAGMENTS (THE SPCP CLONES )RETRIEVED BY MARCType 1Type 2Type 3System CCCFSCC SCF PSCF CR CC CF SCC SCF PSCF CR CCCFSCC SCFPSCF CR J a v aFreecol 93251275622.313195259286324.32492557997818022.52147jEdit 151********.187115531276211.6746399200951108 5.3764Plandora 77297510 3.365160633240.63238117481948 2.7444Carol 31154155133.113930185175831.3580693002212742.33481OpenYMSG 10243833.3371022000.004011271614.2810CCtags 11293620.68319464817.39456168153319.6421QMailAdmin 15493612.243114312 4.65113774810.384GNUMake Uniproc 14430836 1.9432869000.005719925 2.513C #MonoOSC 4213628.573361233.33192381773.9110GreenShot 16837924 1.05236141112215.601167279153211.4619P y t h o n Pyevolve 52117000.0013543611.113251234118.9413Ocemp 1950000.002460000.006116736 3.593Noora 4311441815.7837840000.00261263107.9412CC =Number Clone Classes CF =Number of cloned fragments SCC =Number of SPCP Clone classes CR =Count of Rules SCF =Number of cloned fragments that followed SPCP (i.e.,the SPCP clones)PSCF =Percentage of SPCPclonesFig.5.Overall percentages of cloned fragments that followed SPCPof SPCP clones of a particular type (T i )of a particular subject system,and CF T i stands for the total number of clones of type T i in a particular system.We also calculate the overall percentage of SPCP clones considering all subject systems and all clone-types in a similar way.These overall percentages (Overall-PSCFs)are shown Fig. 5.From this graph it is clear that a considerable amount (i.e.,97.05%,89.13%,90.2%,and 92.96%for Type 1,Type 2,Type 3,and overall case respectively)of clone fragments (i.e.,the clone fragments that did not follow SPCP)can be filtered out from our consideration during refactoring because,these cloned fragments either evolved independently or rarely changed.This reduction in the number of considerable refactoring candidates can minimize refactoring effort and cost.We answered the following four research questions by analyzing the SPCP clones and rules retrieved by MARC.A.Answer to research question RQ 1:Are the changes oc-curring to the clone fragments in SPCOs (similarity preserving co-changes)consistency ensuring changes?To answer this question we manually analyzed 485SPCOs occurred in the SPCPs of 150rules (considering Type 3case of Carol)involving 73SPCP clones.For each of 100rules,the support value (SPCO count)was greater than 1(highest support =7).Each of the remaining rules had a support of 1.We know that the clone blocks in each of the rules retrieved by MARC followed an SPCP.The support value of a rule is equal to the number of SPCOs in the SPCP of the rule.While examining the SPCP of a rule our tool stores:(1)The list of commit(s)where the SPCO(s)occurred.(2)Start and end line numbers of each of the participating clone blocks before and after every commit in the above list.Suppose the clone blocks regarding a particular rule are CB 1and CB 2respectively and they received an SPCO in commit C i applied on revision R i .Then,for each of these clone blocks we collect the snapshot in revision R i and the snapshot in revision R i +1using the line numbers.For each clone block we determine the differences of the correspond-ing snapshots.Then,we manually compare the changes that occurred to CB 1with those that occurred to CB 2and decide whether the changes were consistent or not.Investigation details.Among 485SPCOs that we analyzed manually,in 477SPCOs (98.35%),the changes to the par-ticipating clone blocks (i.e.,SPCP clones)were consistent.According to our observation,in each of these 477SPCOs,the corresponding lines (the same or similar lines)of the two participating SPCP clones were changed in the same or similar way.Thus,the changes in these 477SPCOs can be termed as consistency ensuring changes to clones.In each of the remaining eight SPCOs,the changes to the clone blocks were not consistent.However,the associated clone blocks still preserved their similarity even after these eight SPCOs.An example of the consistency ensuring changes that oc-curred to two clone blocks (corresponding to a rule)in an SPCO on commit 51of Carol is presented in Fig.6.The method bind and the method destroySubcontext in Fig.6are Type 3clones (full method clone)of each other according to the clone detection results of NiCad.From Fig.4we see that the rule consisting of these two clone blocks has a support of 7.That is,these two clone blocks received seven SPCOs (i.e.,similarity preserving co-changes)in their SPCP (i.e.,similarity preserving change pattern).These SPCOs occurred in commits:42,51,54,58,91,153,and 156respectively.The details of the co-changes in commit 51(Fig.6)demonstrate that the changes occurred to the two clone blocks (i.e.,method clones),bind and destroySubcontext ,are consistent.As demonstrated in the figure,almost the same if-blocks were added just after the first line in each of these method clones in revision 52.The only differences in these two if-blocks are in the method names and parameters.Also,lines 9to 12(in revision 51)in each of the method clones were changed in。