Retrieving and classifying instances of source code plagiarism

Automatic detection of source code plagiarism is an important research field for both the commercial software industry and within the research community. Existing methods of plagiarism detection primarily involve exhaustive pairwise document comparison, which does not scale well for large software collections. To achieve scalability, we approach the problem from an information retrieval (IR) perspective. We retrieve a ranked list of candidate documents in response to a pseudo-query representation constructed from each source code document in the collection. The challenge in source code document retrieval is that the standard bag-of-words (BoW) representation model for such documents is likely to result in many false positives being retrieved, because of the use of identical programming language specific constructs and keywords. To address this problem, we make use of an abstract syntax tree (AST) representation of the source code documents. While the IR approach is efficient, it is essentially unsupervised in nature. To further improve its effectiveness, we apply a supervised classifier (pre-trained with features extracted from sample plagiarized source code pairs) on the top ranked retrieved documents. We report experiments on the SOCO-2014 dataset comprising 12K Java source files with almost 1M lines of code. Our experiments confirm that the AST based approach produces significantly better retrieval effectiveness than a standard BoW representation, i.e., the AST based approach is able to identify a higher number of plagiarized source code documents at top ranks in response to a query source code document. The supervised classifier, trained on features extracted from sample plagiarized source code pairs, is shown to effectively filter and thus further improve the ranked list of retrieved candidate plagiarized documents.     

遥感与GIS支持下的中国森林植被动态变化分析

为了研究中国森林植被的时空变化 ,该文在遥感技术与GIS技术的支持下 ,对中国近 5a来森林植被动态变化进行了定量研究。首先通过空间分析 ,对森林植被的空间分布格局进行了分析。同时通过空间差异分析、流失流向分析以及重心迁移分析 ,对森林植被的时空变化进行了分析 ,并对森林植被时空变化的机制与驱动因子进行了探讨。分析结果表明 :我国土地利用格局主要由草地、林地、未利用地和耕地为主 ,其中 ,草地面积最大 ,林地与草地在空间分布上都存在纬度、经度和垂直方向上的三度空间规律性变化 ;5a中林草地变化的总趋势是减少的 ,耕地的增加主要以减少林草地为代价的 ,5a间林地重心向西南方向迁移 4km ,草地重心向南偏西方向迁移 2 .7km ;经济发展加速、人类活动增强是导致林草地减少的主要原因。     

浙江省耕地数量演变及其驱动力研究

选取了近25年浙江省耕地面积统计数据,利用GIS技术、主成分分析,研究了浙江省近25年来耕地面积变化的总体趋势、空间差异和驱动力。结果表明:改革开放以来,浙江省耕地变化总体呈逐年下降趋势且耕地变化空间差异较大;经济增长是形成浙江省耕地数量变化的主要宏观驱动因子,耕地快速减少在发生时间上与经济发展的增长基本同步;在空间分布上具有与地区间经济发展速度和水平的差异相一致的特点。     

Data Mining to Combat Terrorism and the Roots of Privacy Concerns

Recently, there has been a heavy debate in the US about the government’s use of data mining in its fight against terrorism. Privacy concerns in fact led the Congress to terminate the funding of TIA, a program for advanced information technology to be used in the combat of terrorism. The arguments put forward in this debate, more specifically those found in the main report and minority report by the TAPAC established by the Secretary of Defense to examine the TIA issue, will be analysed to trace the deeper roots of this controversy. This analysis will in turn be used as a test case to examine the adequacy of the usual theoretical frameworks for these kinds of issues, in particular the notion of privacy. Whereas the dominant theoretical framing of the notion of privacy turns around access to information, most of the core arguments in the debate do not fit in this kind of framework. The basic disagreements in the controversy are not about mere access, they involve both access and use. Furthermore, whereas the issue of access by itself refers to a more or less static situation, the real disagreements much more concern the organisational dynamics of the use of information, the mechanisms in the organisation that control these dynamics, and the awareness present within the organisation of the ‘social risks’ these dynamics represent. The bottom line question is whether the assessment of these gives sufficient reason for trust.     

Japanese Conceptions of Privacy: An Intercultural Perspective

This paper deals with intercultural aspects of privacy, particularly with regard to important differences between Japanese and the Western views. This paper is based on our discussions with Rafael Capurro – a dialogue now represented by two separate but closely interrelated articles. The companion paper is broadly focused on the cultural and historical backgrounds of the concepts of privacy and individualism in “Western” worlds; our main theme focuses on different concepts of privacy in Japan and their sources in related aspects of Japanese culture. The interrelationship between our two papers is apparent in our taking up identical or similar topics in each paper. Reading our two papers in conjunction with each other will bring about deeper and broader insights into the diverse values and worldviews of Japan and Western cultures that underlie concepts of privacy that at a surface level appear to be similar     

Parents of Traditionally Aged Community College Students: Communications and Choice

Five suburban community colleges in a metropolitan area collaborated on a survey to parents of high school graduates of the class of 2002 who attended the colleges in fall 2002. The study was undertaken to learn more about parents roles in their students selection of community colleges, to give insights and information about this important community college constituency, and to assist community colleges to shape more effective ways to foster positive and supportive opinions among parents of potential students. Parents want the community college to provide students with credits and grade point averages enabling transfer, overestimate their students academic skills as measured by course placement tests, engaged in a number of college-choice activities, and indicate that factors associated with lifestyle and money were major reasons for selecting the community college. Associations between parents social capital and perceptions of their students academic abilities were found for a number of dependent variables examined. The study also revealed important differences in how participating institutions record and calculate key measures such as credits earned and grade point averages.     

Field-study science classrooms as positive and enjoyable learning environments

We investigated differences between field-study classrooms and traditional science classrooms in terms of the learning environment and students’ attitudes to science, as well as the differential effectiveness of field-study classrooms for students differing in sex and English proficiency. A modified version of selected scales from the What Is Happening In this Class? questionnaire was used to assess the learning environment, whereas students’ attitudes were assessed with a shortened version of a scale from the Test of Science Related Attitudes. A sample of 765 grade 5 students from 17 schools responded to the learning environment and attitude scales in terms of both their traditional science classrooms and classrooms at a field-study centre in Florida. Large effect sizes supported the effectiveness of the field-studies classroom in terms of both the learning environment and student attitudes. Relative to the home school science class, the field-study class was considerably more effective for students with limited English proficiency than for native English speakers.