网络考试系统的设计与实现毕业设计论文.doc

毕毕 业业 设设 计计( 论论 文文) 网络考试系统的设计与实现网络考试系统的设计与实现 考试子系统考试子系统 论论文作者姓名：文作者姓名： 申申请请学位学位专业专业： ： 申申请请学位学位类别类别： ： 指指导导教教师师姓姓名名（ （职职称称） ）： ： 论论文提交日期：文提交日期： 网络考试系统的设计与实现网络考试系统的设计与实现 考试子系统考试子系统 摘摘 要要 随着教育思想的更新和科学技术的进步，以纸和笔为主要工具的传统考试 方式的诸多弊端越来越突出的显现出来。试卷的设计、组织、印刷、分发、考 试等将耗费大量的人力物力,而且工作效率低下、主观性较强。针对这一现状， 基于网络的考试系统应运而生。网络考试系统突破了传统考试方式的时空限制， 使考试方式更为灵活，同时充分利用计算机进行自动出题等功能，大大减轻了 管理人员和教师的工作量。 本设计的开发是基于 b/s 结构，采用 asp 程序设计语言及 access 数据库 进行设计与开发；本文首先介绍系统开发环境和运行平台、asp 编程技术及数 据库的相关知识，并对网络考试子系统的设计进行了详细的需求分析；然后给 出了网络考试子系统的设计方案及系统的具体实现步骤，主要功能包括新闻发 布、网络考试、题库管理等功能模块；最后，通过综合测试与分析，说明该系 统运行稳定、可靠，具有一定的实用价值。 关键词关键词：网络考试；b/s 结构；题库管理；数据库；asp 编程技术 design and implementation of online exam system exam subsystem abstract with the improvement of education and science technology, the shortcomings in traditional exam system, which mainly uses paper and pen as its main tools, become increasingly obvious. the design, building, printing, distribution, tests of the examination paper will cost lots of manpower and materials. moreover the working efficiency is low, the subjectivity is stronger. in view of this present situation, the online exam system based on the network arises at the historic moment. the network exam system breaks through the space and time limitation in the traditional test, which causes the test way to be more nimble, simultaneously makes full use of the computer automatically setting the examination paper and so on, and greatly reduces the administrative personnel and teachers work load. this paper introduces design and implementation of exam subsystem based on b/s, with access database applications and asp programmingat first, this paper introduces development condition, platform, asp programming technology, database, etc, and the demands for the online exam system are analyzed in detail. then it produces the design idea and concrete implement steps of this system. the systems functions mainly include news issuing, the management of examination room, online exam, the management of item pool and so on. at last, by testing and analyzing, it shows that the system runs stably and reliably, which has some practical value. key words: online exam; b/s structure; management of item pool; database; asp programming technology 目目 录录 论文总页数：25 页 1 引言1 1.1 背景1 1.2 国内外研究现状.1 1.3 本系统研究的意义.1 1.4 本系统的研究方法.1 1.5 本文的主要工作.2 1.5.1 研究的主要内容2 1.5.2 论文各章节安排2 2 系统需求分析2 2.1 网络考试系统的发展概况2 2.2 本系统的需求分析.2 2.2.1 新闻管理2 2.2.2 考试管理2 2.2.3 试卷生成2 2.2.4 考场管理3 2.2.5 题库管理3 2.2.6 科目管理3 2.2.7 系统初始化3 3 考试子系统的总体设计4 3.1 开发工具及开发环境.4 3.1.1 开发工具4 3.1.2 程序的运行环境4 3.2 系统设计4 3.3 数据库设计.5 3.3.1 数据库类型5 3.3.2 数据库需求分析5 3.3.3 数据库物理设计5 3.3.4 数据库逻辑设计5 3.3.5 数据库表的字段定义6 4 考试子系统的具体实现8 4.1 考前管理模块8 4.1.1 流程分析8 4.1.2 效果图8 4.1.3 代码分析9 4.2 考场管理模块.12 4.2.1 流程分析12 4.2.2 效果图13 4.2.3 代码分析13 4.3 题库管理模块.15 4.3.1 流程分析15 4.3.2 效果图15 4.3.3 代码分析15 4.4 其他模块19 4.4.1 流程分析19 4.4.2 效果图19 4.4.3 代码分析19 5 系统综合测试与分析20 5.1 系统综合20 5.2 系统测试与分析.20 5.3 系统分析21 结 论22 参考文献23 致 谢24 声 明25 第 1 页 共 25 页 1 引言引言 1.1 背景背景 伴随着网络技术的飞速发展，网络技术已经应用到我们生产和生活的各个 方面，成为不可缺少的工具。随着科技的进步与经济的繁荣，校园计算机网络 的建立与应用已相当普遍，我们可以在已经建成的校园网上开发网络考试系统， 发挥网络的资源整和优势，使有限的资源得到充分的利用，加大信息的流动效 率，实现信息量的相对增加。这样，一方面可以使当前相当急迫的人与资源的 矛盾得到高效、合理的解决；另一方面又实现了教学工作的信息化，符合当今 社会发展的方向，并为以后的改进和发展提供了余地。 1.2 国内外研究现状国内外研究现状 internet 技术的发展使得考试的技术手段和载体发生了革命性的变化，inter net 的开放性、分布性的特点和基于 internet 的巨大的计算能力使得考试突破了 时间和空间的限制。基于 internet 的考试系统正成为国内外教育机构的研究热点 之一。与传统考试模式相比，网上考试具有无可比拟的优越性，它可以将传统 考试过程中的各个环节缩小到一至两个环节，几乎屏蔽了所有人工直接干预考 试活动的可能性，不但能够节约大量的时日、人力、物力与财力，而且还可以 大幅度提高考试成绩的客观性和公正性。 1.3 本系统研究的意义本系统研究的意义 本毕业设计的目的主要是为了检查综合运用以前所学知识（包括以前所学 的一些关于网络技术、编程技术、数据库、网络与信息安全等知识）的能力。 开发一个网络考试系统，既能锻炼自己的实际动手能力，又能引导自己进行一 次模拟实际产品的开发，对于以后工作能力的培养具有重要的意义。 1.4 本系统的研究方法本系统的研究方法 本毕业设计要求设计一个功能较完善的网络考试系统，实现在线试卷的生 成、在线考试、题库的设计、管理与维护等功能。因此，本次毕业设计应首先 分析网络考试系统的相关功能，结合本次毕业设计的相关要求写出需求分析； 其次，综合运用以前所学的相关知识（包括计算机网络技术、编程技术、数据 库、信息安全等相关知识） ，选择所熟悉的开发工具进行本毕业设计的开发；在 设计中以需求分析为基础，写出系统开发计划、实现流程及相关问题的实现方 法；同时，在开发设计与实现中，要保存好相关的设计文挡，为后面的毕业论 文的写作准备材料；最后，系统开发完毕后，进行调试和试运行，做好调试和 试运行的相关记录，也为后面的毕业论文的写作准备材料。 第 2 页 共 25 页 1.5 本文的主要工作本文的主要工作 1.5.1 研究的主要内容研究的主要内容 综合运用以前所学的专业知识，设计开发一个网络考试系统，本设计要求 完成部分任务在线试卷的生成、在线考试、题库的设计、管理与维护等功 能，具体包括以下内容。 （1）在线试卷的生成：要求采用动态页面生成技术。 （2）在线考试：考生输入准号证号登陆系统成功后，选择对应的试卷可进 行考试。答题完毕后，有倒计时的功能，可自动交卷等功能。 （3）题库的设计、管理与维护：包括考题的录入、增加、删除、查询等功 能。 （4）在线考试的安全问题：包括考生身份的安全认证、考试时间的控制等。 1.5.2 论文各章节安排论文各章节安排 本文首先对考试子系统的设计进行了详细的需求分析，接着介绍系统开发 环境和运行平台、asp 编程技术及数据库的相关知识；然后给出了考试子系统 的设计方案及系统的具体实现步骤，主要功能包括在线试卷的生成、在线考试、 题库的设计、在线考试的安全问题等功能模块；最后，通过综合测试与分析得 出结论。 2 系统需求分析系统需求分析 2.1 网络考试系统的发展概况网络考试系统的发展概况 随着 internet 在我国的迅速发展，远程教育和校园的信息化建设已经成为网 络应用的一个新的热点，网上考试作为远程教育和校园信息化建设的一部分有 着其独特的需求和作用。在新的教学模式中，极大地提高了教学的灵活性和效 率。 相比传统的考试形式，网上考试系统的主要好处是一方面可以动态管理各 种考试信息，只要准备足够大的题库，就可以按要求自动生成各种试卷；另一 方面，考试时间灵活，可以在规定的时间段内的任意时间参加考试。 2.2 本系统的需求分析本系统的需求分析 2.2.1 新闻管理新闻管理 可以添加、修改、删除新闻，系统将在首页显示最新的 5 条新闻。 2.2.2 考试管理考试管理 可以发布、修改、删除多个考场信息；可以动态设定各种题型数量和分值； 考场试卷没有生成之前可以修改考试信息，生成之后将不能再修改考试信息。 第 3 页 共 25 页 2.2.3 试卷生成试卷生成 对刚发布的考场根据题型、数量、对应考生自动生成试卷。 2.2.4 考场管理考场管理 对生成试卷待考的考场宣布开考，同时生成一个属于此考场的随机验证密 码（考生登陆考场时，监考教师提供给考生） ，对考场进行管理包括对单一考生 实行锁定、解锁、交卷，或者对一个考场全部考生实行全部锁定、全部解锁、 全部交卷操作。被锁定的考生将不能继续答卷。此外，被锁定的考生、已经登 陆非法退出考试界面的考生、不能提供考场随机验证密码的考生都不能登陆考 试系统。 （可以最大限度的杜绝考试作弊事件的发生）未登陆的考生、被解锁的 考生需要提供考场随机验证密码、考生准考证号码、考生账号密码才能够登陆 考试系统，进行在线考试。交卷后，考生本人或者监考教师均不能再修改考试 信息。 2.2.5 题库管理题库管理 用户可以在线对题库中试题进行添加、编辑、删除等维护操作；单选题、 多选题选项不限定个数、系统会自动判定；系统首页会显示题库中各题型题量 信息。 对题库的批量上传请直接使用数据的导入导出，题库在表 quilib 中，参数 名和字段名说明如下。 （1）id试题编号：索引、自动编号、用户不能干预。 （2）subjid科目编号：根据科目 subject 表中对应 id 设置。 （3）quiztitle试题题干：就是题目。 （4）quizclass试题类型：radio1 为判断题,radio2 为单选题,checkbox 为多 选题,text 为填空题。 （5）quizoption试题选择项：各选择项之间用“|“隔开，开头无需加 abc 等字母，从前往后依次为 abcd 等选择项，系统会自动判断，判断和填空题留 空。 （6）quizkey试题答案：判断题中 a 为正确，b 为错误。 （7）quizhits试题命中次数：系统出卷时被抽中次数，开始为 0。 （8）quizkeyok考生答对次数：开始为 0。 （9）quizwriter试题作者。 （10）quiztime试题添加时间。 2.2.6 科目管理科目管理 科目管理实现添加、修改、删除科目等功能。 第 4 页 共 25 页 2.2.7 系统初始化系统初始化 系统初始化实现删除已经考场安排信息、考生答卷信息、考生试卷信息等 功能。 3 考试子系统的总体设计考试子系统的总体设计 3.1 开发工具及开发环境开发工具及开发环境 3.1.1 开发工具开发工具 根据系统开发的要求和需要本系统在开发过程中应用到的系统开发工具主 要有。 （1）asp 代码编写：ultraedit 10.00c。 （2）图形图像处理：photoshop 7.0。 （3）页面设计：macromedia dreamweaver mx。 （4）数据库：access 2003。 3.1.2 程序的运行环境程序的运行环境 本系统的开发环境主要包括硬件和软件两方面，由于系统本身需要软件、 硬件的支持，它对软硬件环境的需求如下。 （1）硬件环境：服务器：pvi1.8g 以上+256m 内存+40g 以上硬盘 +10/100m 网卡以上。 （2）软件环境： windows 2003 server+iis5.5+ie6.0。 3.2 系统设计系统设计 系统在进行结构设计时，主要分为了教师管理结构和考生考试结构。 （1）教师管理结构，如图 1 所示。 第 5 页 共 25 页 图 1 教师管理结构 图 2 考生考试结构 （2）考生考试结构构建，如图 2 所示。 3.3 数据库设计数据库设计 3.3.1 数据库类型数据库类型 在设计本系统的数据库时，考虑到系统实现的灵活性，还有对系统后台数 据维护的方便，采用了 access 2003 数据库系统。该数据库管理系统适合解决大 量数据的管理工作，操作灵活、转移方便、运行环境简单，对于中小型网站的 数据库处理能力效果显著。 3.3.2 数据库需求分析数据库需求分析 根据网络考试系统的需求，设计如下所示的数据项和结构。 （1）题库信息：包括科目、考试题目、答案、班级、选项、考试时间、出 题人等数据项。 （2）试卷信息：包括学生 id、考试 id、试卷 id、考试班级、考试答案、 学生分数等。 （3）学生信息：包括学生编号、学号、姓名、性别、班级、生日等。 （4）新闻信息：包括新闻题目、新闻消息、发布人、发布时间等。 本系统建立了一个完善的后台数据库系统，通过该数据库能够管理整个考 试系统所需的信息。 3.3.3 数据库物理设计数据库物理设计 数据库名 ol_test，设计数据库的物理文件及相关属性如下。 （1）主数据文件：quizlib.mdf。 第 6 页 共 25 页 （2）最大文件大小：不受限。 （3）初始空间：3.80mb。 3.3.4 数据库逻辑设计数据库逻辑设计 图 3 数据库逻辑设计 ol_test 的数据库里包含用户数据对象和系统数据对象两大部分,其中系统数 据对象由系统自动产生，用户数据对象是由设计人员根据需要设计。下面给出 的数据库逻辑设计图，如图 3 所示。 3.3.5 数据库表的字段定义数据库表的字段定义 （1）考试信息表（如表 1 所示） 。 表 1 考试信息表（admininfo） 字段名数据类型长度重复默认值允许为空描述 id自动编号长整型nn newstitle文本255yn newsinfo文本50nn newswriter文本50nn newstime日期/时间n newshits数字长整型nn （2）学生信息表（如表 2 所示） 。 表 2 学生信息表（stuinfo） 字段名数据类型长度重复默认值允许为空描述 id文本50nn stuname文本255nn stupwd文本50nn 第 7 页 共 25 页 stusex是/否n stuabirthday日期/时间n gradeid文本50n classid文本50n （3）学生试卷信息表（如表 3 所示） 。 表 3 学生试卷表（stupaper） 字段名数据类型长度重复默认值允许为空描述 id自动编号长整型nn stuid文本500n eaxmid数字长整型0n paperid数字长整型0n quizid数字长整型0n quizclass文本50n quizkey文本255n quizstatus是/否n quizscore数字长整型0n stukey文本255n stuscore数字长整型0n （4）学生成绩表（如表 4 所示） 。 表 4 学生成绩表（stuscore） 字段名数据类型长度重复默认值允许为空描述 id自动编号长整型nn stuid文本50n stupwd文本50nn eaxmid数字长整型0n quizid数字长整型0n quizkey文本255n stukey文本255n stustatus文本50n stuscore数字长整型0n （5）科目表（如表 5 所示） 。 第 8 页 共 25 页 表 5 科目表（subject） 字段名数据类型长度重复默认值允许为空描述 id自动编号长整型nn subjname文本50n subjinfo文本50n （6）题库信息表（如表 6 所示） 。 表 6 题库信息表（quizlib） 字段名数据类型长度重复默认值允许为空描述 id自动编号长整型nn subjid数字长整型0n knlgid数字长整型0n quiztitle备注n quizclass文本50n quizoption文本50n quizkey文本50yn quizhits数字长整型0n quizkeyok数字长整型0n quizwriter文本50n quiztime日期/时间n 4 考试子系统的具体实现考试子系统的具体实现 考试子系统主要由考前管理模块、考场管理模块、题库管理模块、其它模 块构成，下面主要详细讲述各个模块的具体实现过程。 4.1 考前管理模块考前管理模块 4.1.1 流程分析流程分析 如图 4 所示，是考前模块的程序流程分析。 第 9 页 共 25 页 图 4 考前模块程序流程 4.1.2 效果图效果图 添加新闻时的效果图如图 5 所示。 图 5 添加新闻 考试信息发布时的效果图如图 6 所示。 图 6 考试信息发布 4.1.3 代码分析代码分析 考前管理模块涉及到新闻的发布和管理，考试信息的发布和管理，以及系 第 10 页 共 25 页 统试卷的自动生成和手工生成。而生成试卷的算法和代码又是本系统的核心算 法和代码。 新闻发布和管理主要由 show(newsid)、edit(newsid)、saveedit(newsid)、 del(newsid)、savedel(newsid)、add()、saveadd()、list()几个函数来实现。 考试信息的发布和管理其实也是一个较为复杂的过程，它由 test(examid)、 show(examid)、edit(examid)、saveedit(examid)、del(examid)、savedel(examid)、 add()、saveadd()、saveadd()等函数来实现。 虽然新闻发布和管理的实现函数和考试信息的发布有着一些相似性，但后 者的操作和过程显得更复杂。后者还涉及到分页机制，需要 listpages3()函数来 实现。在涉及到考试时间时，又要使用 checkform(theform)函数。此外考试信 息的发布和管理还使用了 checkquizcount()、checkquizcount()来检查题库中题 量的数目和考生的身份。 试卷的生成主要有两个 makepaper()、mkpaper()函数来实现手工和自动出题， 下面给出两函数的具体代码。 function makepaper(examid) dim stuid,stugrade,stuclass,radio1sum,radio1val,radio2sum,radio2val,checkboxsum,checkboxval, textsum,textval,exampwd 查出考试信息 sqlexam=“select * from examinfo inner join subject on subject.id = examinfo.subjid where examstatus=exam and examinfo.id=“ if i pursue you i will not catch you, and if i catch you-through your own slowness and clumsiness-i will not kill you, and if i kill you i will not eat you.“ nicholas had begun to back away, and at the last; words, realizing that they were a signal, he turned and began to run, splashing through the shallow water. ignacio ran after him, much helped by his longer legs, his hair flying behind his dark young face, his square teeth-each white as a bone and as big as nicholass thumbnail-showing like spectators who lined the railings of his lips. “dont run, nicholas,“ dr. island said with the voice of a wave. “it only makes him angry that you run.“ nicholas did not answer, but cut to his left, up the beach and among the trunks of the palms, sprinting all the way because he had no way of knowing ignacio was not right behind him, about to grab him by the neck. when he stopped it was in the thick jungle, among the boles of the hardwoods, where he leaned,.; out of breath, the thumping of his own heart the only . sound in an atmosphere silent and unwaked as earths long, prehuman day. for a time he listened for any sound ignacio might make searching for him; there was none. he drew a deep breath then and said, “well, thats over,“ expecting dr. island to answer from somewhere; there was only the green hush. the light was still bright and strong and nearly, shadowless, but some interior sense told him the day, was nearly over, and he noticed that such faint shades as he could see stretched long, horizontal distortions of their objects. he felt no hunger, but he had fasted be- fore and knew on which side of hunger he stood; he was not as strong as he had been only a day past, and by this time next day he would probably be unable to outrun ignacio. he should, he now realized, have eaten the monkey he had killed; but his stomach revolted at the thought of the raw flesh, and he did not know how he might build a fire, although ignacio seemed to have done so the night before. raw fish, even if he were able to catch a fish, would be as bad, or worse, than raw monkey; he remembered his effort to open a coconut-he had failed, but it was surely not impossible. his mind was hazy as to what a coconut might contain, but there had to be an edible core, because they were eaten in books. he decided to make a wide sweep through the jungle that would bring him back to the beach well away from ignacio; he had several times seen coconuts lying in the sand under the trees. he moved quietly, still a little afraid, trying to think of ways to open the coconut when he found it. he imagined himself standing before a large and raggedly faceted stone, holding the coconut in both hands. he raised it and smashed it down, but when it struck it was no longer a coconut but mayas head; he heard her nose cartilage break with a distinct, rubbery snap. her eyes, as blue as the sky above madhya pradesh, the sparkling blue sky of the egg, looked up at him, but he could no longer look into them, they retreated from his own, and it came to him quite suddenly that lucifer, in falling, must have fallen up, into the fires and the coldness of space, never again to see the warm blues and browns and greens of earth: 1 was watching satan fall as lightning from heaven. he had heard that on tape somewhere, but he could not remember where. he had read that on earth lightning did not come down from the clouds, but leaped up from the planetary surface toward them, never to return. “nicholas.“ he listened, but did not hear his name again. faintly water was babbling; had dr. island used that sound to speak to him? he walked toward it and found a little rill that threaded a way among the trees, and followed it. in a hundred steps it grew broader, slowed, and ended in a long blind pool under a dome of leaves. . diane was sitting on moss on the side opposite him; she looked up as she saw him, and smiled. “hello,“ he said. “hello, nicholas. i thought i heard you. i wasnt mistaken after all, was i?“ “i didnt think i said anything.“ he tested the dark water with his foot and found that it was very cold. 第 28 页 共 25 页 “you gave a little gasp, i fancy. i heard it, and i said to myself, thats nicholas, and i called you. then i thought i might be wrong, or that it might be ignacio.“ “ignacio was chasing me. maybe he still is, but h think hes probably given up by now.“ the girl nodded, looking into the dark waters of they pool, but did not seem to have heard him. he began to work his way around to her, climbing across the snakelike roots of the crowding trees. “why does ignacio want to kill me, diane?“ “sometimes he wants to kill me, too,“ the girl said. “but why?“ “i think hes a bit frightened of us. have you ever talked to him, nicholas?“ “today i did a little. he told me a story about a pet fish he used to have.“ “ignacio grew up all alone; did he tell you that? on= earth. on a plantation in brazil, way up the amazon -dr. island told me.“ “i thought it was crowded on earth.“ “the cities are crowded, and the countryside closes to the cities. but there are places where its emptie than it used to be. where ignacio was, there would have been red indian hunters two or three hundred years ago; when he was there, there wasnt anyone, just the machines. now he doesnt want to be looked at, doesnt want anyone around him.“ nicholas said slowly, “dr. island said lots of people wouldnt be sick if only there werent other people around all the time. remember that?“ a “only there. are other people around all the time; thats how the world is.“ “not in brazil, maybe,“ nicholas said. he was trying to remember something about brazil, but the only thing he could think of was a parrot singing in a straw hat from the comview cartoons; and then a turtle and a hedgehog that turned into armadillos for the love of god, montressor. he said, “why didnt he stay there?“ “did i tell you about the bird, nicholas?“ she had been not listening again. “what bird?“ “i have a bird. inside.“ she patted the flat stomach below her small breasts, and for a moment, nicholas thought she had really found food. “she sits in here. she has tangled a nest in my entrails, where she sits and tears at my breath with her beak. i look healthy to you, dont i? but inside im hollow and rotten and turning brown, dirt and old feathers, oozing away. her beak will break through soon.“ “okay.“ nicholas turned to go. “ive been drinking water here, trying to drown her. i think ive swallowed so much i couldnt stand up now if i tried, but she isnt even wet, and do you know something, nicholas? ive found out im not really me, im her.“ turning back nicholas asked, “when was the last time you had anything to eat?“ “i dont know. two, three days ago. ignacio gave me something.“ “im going to try to open a coconut. if i can ill bring you back some.“ when he reached the beach, nicholas turned and walked slowly back in the direction of the dead fire, this time along the rim of dampened sand between the sea and the palms. he was thinking about machines. there were hundreds of thousands, perhaps millions, of machines out beyond the belt, but few or none of the sophisticated servant robots of earth-those were luxuries. would ignacio, in brazil (whatever that was like), have had such luxuries? nicholas thought not; those robots were almost like people, and living with them would be like living with people. nicholas wished that he could speak brazilian. there had been the therapy robots at st. johns; nicholas had not liked them, and he did not think ignacio would have liked them either. if he had liked his therapy robot he probably would not have 第 29 页 共 25 页 had to be sent here. he thought of the chipped and rusted old machine that had cleaned the corridors-maya had called it corradora, but no one else ever called it any- f thing but hey! it could not (or at least did not) speak, 1 and nicholas doubted that it had emotions, except possibly a sort of love of cleanness that did not extend to its own person. “you will understand,“ someone was saying inside his head, “that motives of all sorts can be divided into two sorts.“ a doctor? a therapy robot? it did not matter. “extrinsic and intrinsic. an extrinsic motive has always some further end in view, and that end we call an intrinsic motive. thus when we have reduced motivation to intrinsic motivation we have reduced it to its simplest parts. take that machine over there.“ what machine? “freud would have said that it was fixated at the latter anal stage, perhaps due to the care its builders exercised in seeing that the dirt it collects is not released again. because of its fixation it is, as you see, obsessed with cleanliness and order; compulsive sweeping and scrubbing palliate its anxieties. it is a strength of freuds theory, and not a weakness, that i