Implementing Global Constraints as Graphs of Elementary Constraints

合集下载

时序关联规则算法公式

时序关联规则算法公式
时序关联规则算法是一种用于发现时间序列数据中的关联规则的方法。

其主要思想是利用时间序列数据中的时间顺序信息，来发现不同时间点之间的关联规则。

一种常见的时序关联规则算法是基于序列模式挖掘的方法，其中常用的算法包括PrefixSpan算法和GSP算法。

PrefixSpan算法是一种基于前缀投影的序列模式挖掘算法，其主要思想是通过递归地构建序列的前缀投影来发现频繁序列模式。

该算法的公式可以表示为：
PrefixSpan(S, α, β, P)。

其中，S是输入的时间序列数据集，α是最小支持度阈值，β是最小序列长度阈值，P是当前的序列前缀。

另一种常见的时序关联规则算法是GSP算法（Generalized Sequential Pattern algorithm），该算法通过扫描数据库多次来发现频繁序列模式。

其公式可以表示为：
GSP(S, α, β)。

其中，S是输入的时间序列数据集，α是最小支持度阈值，β是最小序列长度阈值。

除了这两种算法外，还有一些基于时间序列数据的关联规则挖掘算法，它们的公式可能会有所不同，但总体思想是类似的，即利用时间序列数据中的时间顺序信息来挖掘关联规则。

这些算法的公式通常会涉及到支持度和置信度等概念，用于衡量发现的关联规则的重要程度和可靠性。

总的来说，时序关联规则算法的公式会涉及到时间序列数据的输入、最小支持度阈值、最小序列长度阈值等参数，以及算法内部的递归或迭代过程，用于发现频繁序列模式或关联规则。

这些公式的具体形式会根据具体的算法而有所不同，但都是为了在时间序列数据中发现有意义的关联规则。

liquibase constraints使用方式

Liquibase 是一个用于跟踪、管理和应用数据库更改的开源数据库版本控制工具。

在Liquibase 中，可以使用约束（constraints）来定义数据库表中的数据完整性规则。

以下是使用Liquibase 添加约束的示例：在changeLog 文件中定义约束:在changeLog 文件中，可以使用addUniqueConstraint 和addCheckConstraint 命令来添加唯一约束和检查约束。

xml<changeSet id="addUniqueConstraint" author="your_name"><addUniqueConstraint tableName="your_table_name" columnNames="column1, column2" constraintName="unique_constraint_name"/></changeSet><changeSet id="addCheckConstraint" author="your_name"><addCheckConstraint tableName="your_table_name" columnName="column_name" checkExpression="column_value > 0" constraintName="check_constraint_name"/></changeSet>在SQL 文件中定义约束:在SQL 文件中，可以直接编写SQL 语句来添加约束。

sqlALTER TABLE your_table_name ADD CONSTRAINT unique_constraint_name UNIQUE (column1, column2);ALTER TABLE your_table_name ADD CONSTRAINT check_constraint_name CHECK (column_value > 0);在Liquibase 中执行变更:在Liquibase 中执行变更，可以使用Liquibase Maven Plugin 或Liquibase Command Line Interface。

软件工程_东北大学中国大学mooc课后章节答案期末考试题库2023年

软件工程_东北大学中国大学mooc课后章节答案期末考试题库2023年1._______ is a discipline whose aim is the production of fault-free software,delivered on time and within budget, that satisfies the client's needs._______是一个学科，其目标是生产出满足客户的需求的、未超出预算的、按时交付的、没有错误的软件。

答案:2.The relationship between whole-class and part-classes is called ______.整体和部分类之间的关系被称为______。

答案:aggregation3.The relationship between super-class and subclasses is called ______.超类和子类之间的关系称为______。

答案:inheritance4.The strategy of inheritance is to use inheritance wherever _______.继承的策略是在_______的情况下使用继承。

答案:appropriate5._____is to encapsulate the attributes and operations in an object, and hides theinternal details of an object as possible. _____是为了在一个对象中封装属性和操作，并尽可能隐藏对象的内部细节。

Data encapsulation6.Two modules are ________ coupled if they have write access to global data.如果两个模块对全局数据具有写访问权限，则是________耦合。

注规原理知识

注规原理知识
注规原理（principle of regularization）是机器学习中一种常用的方法，用于解决过拟合（overfitting）问题。

在机器学习中，模型的目标是通过学习训练数据来预测新的未知数据。

然而，当模型过于复杂时，它可能会在训练数据上表现得非常好，但在新数据上表现不佳。

这种现象被称为过拟合，意味着模型过度“记忆”了训练数据中的噪声和细节，而无法泛化到新的数据。

注规原理的基本思想是在模型的损失函数中引入一个正则化项，以惩罚模型的复杂度。

这个正则化项通常是模型参数的范数，如L1范数或L2范数。

通过增加这个正则化项，可以限制模型参数的大小，从而减少过拟合的风险。

具体地说，注规原理可以通过在损失函数中添加一个正则化项来实现。

例如，在线性回归模型中，我们可以使用最小二乘法来拟合数据，其中损失函数可以写为：
L = (y - Xw)^2 + λ||w||^2
其中，y是目标变量，X是输入特征矩阵，w是模型的权重向量，λ是一个正则化参数，||w||^2表示w的L2范数的平方。

当λ趋近于零时，正则化项的影响变小，模型更容易过拟合。

当λ增大时，正则化项的影响增强，模型更倾向于拟合简单的模式，
从而减少过拟合的风险。

注规原理还可以应用于其他机器学习算法，如逻辑回归、支持向量机等。

通过调整正则化参数，可以平衡模型的复杂度和拟合能力，从而提高模型的泛化性能。

雅思入学测试试卷（真题版）

IELTS Entry Test Paper启德雅思部雅思入学测试试卷雅思入学测试考试日期： 6 考生姓名：6ListeningSECTION 1Questions1-10Complete the notes below.Write NO MORE THAN THREE WORDS AND/OR A NUMBER for each answer.NOTES - Christmas DinnerExample AnswerName to book for ...45...........................Date of dinner: 21 DecemberChoices for venue:·First choice 1........................... Tel. number: not known·Second choice 2........................... Tel. number: 777192·Third choice 3........................... Tel. number: 4........................Price per person: ￡12Restaurant must have vegetarian food and a 5...........................Menu: First course - French Onion Soup OR Fruit JuiceMain course - Roast Dinner OR 6...........................Dessert - Plum Pudding OR Apple Pie- CoffeeRestaurant requires from us:7........................... and letter of confirmationand we must 8........................... in advance.Must confirm in writing by: 9...........................Put notice in 10................................................SECTION2Questions11-20Questions 11-13Complete the table below.Write NO MORE THAN THREE WORDS OR A NUMBER for each answer.MEMBERSHIP OF SPORTS CENTRECost 11 £.........................per12......................Where? 13..........................When? 2 to 6 pm, Monday to ThursdayBring: Union cardPhotoFeeQuestions 14-16Complete the table below.Write NO MORE THAN THREE WORDS for each answer.Always bring sports 14...............................when you come to 15...................or use the Centre'sfacilities.Opening hours 9 am to 10 pm on 16......................10 am to 6 pm on Saturdays50% 'morning discount' 9 am to 12 noon on weekdaysQuestions 17-20Look at the map of the Sports Complex below.Label the buildings on the map of the Sports Complex.Choose your answers from the box below and write them against Questions 17-20.Arts StudioFootball PitchTennis CourtsDance StudioFitness RoomReceptionSquash CourtsSECTION3Questions21-30Complete the form below.Write NO MORE THAN THREE WORDS AND/OR NUMBER for each answer.YOUNG ELECTRONICENGINEER COMPETITION Name(s) of designer(s): John Brown21 ...........................Age: 22...........................Name of design: 23................................................................................Dimensions of equipment: 24Width Length Depth...........................cm ...........................cm ...........................cmPower: BatterySpecial features: 25...................................................................................26...................................................................................27...................................................................................Cost: parts $528....................... $9.50Other comments: need help to make 29...........................would like to develop range of sizesSend by: 30...........................SECTION4Questions31-40Questions 31-33Complete the table below.Write NO MORE THAN TWO WORDS for each answer."NEW" MEAT CAN BE COMPARED TO PROBLEM kangaroo 31........................... 32...........................crocodile chicken fattyostrich 33...........................Questions 34-36Complete the cable belowWrite NO MORE THAN THREE WORDS for each answer.Questions 37-40Choose the correct letters A-C.37 Ostrich meatA has more protein than beef.B tastes nearly as good as beef.C is very filling.38 One problem with ostrich farming in Britain isA the climate.B the cost of transporting birds.C the price of ostrich eggs.39 Ostrich chicks reared on farmsA must be kept in incubators until mature.B are very independent.C need looking after carefully.40 The speaker suggests ostrich farms are profitable becauseA little initial outlay is required.B farmed birds are very productive.C there is a good market for the meat.ReadingREADING PASSAGE1You should spend about 20 minutes on Questions 1-12 which are based on Reading Passage 1 below.THE DEPARTMENT OF ETHNOGRARHYThe Department of Ethnography was created as a separate department within the British Museum in 1946, after 140 years of gradual development from the original Department of Antiquities. It is concerned with the people of Africa, the Americas, Asia, the pacific and parts of Europe. While this includes complex kingdoms, as in Africa, and ancient empires, such as those of the twentieth century focus of attention in the twentieth century has been on small-scale societies. Through its collections, the Department's specific interest is to document how objects are created and used, and to understand their importance and significance to those who produce them. Such objects can include both the extraordinary and the mundane, the beautiful and the banal.The collections of the Department of Ethnography include approximately 300,000 artefacts, of which about half are the product of the present century. The Department has a vital role to play in pro- viding information on non-Western cultures to visitors and scholars. To this end, the collecting emphasis has often been less on individual objects than on groups of mate- rang of a society's cultural expressions. Much of the more recent collecting was carried out in the field, sometimes by Museum staff working on general anthropological projects in collaboration with a wide variety of national governments and other institutions. The material collected includes great technical series-for instance, of textiles from Bolivia. Guatemala, Indonesia and areas of West Africa-or of artefact types such as boats. The latter include working examples of coracles from India, reed boats from lake Titicaca in the Andes, kayaks from the Arctic, and dug-out canoes from several countries. The field assemblages, such as those from the Sudan, Madagascar and Yemen, include a whole range of material culture representative of one people. The might cover the necessities of life of an African herdsman or on Arabian farmer, ritual objects, or even on occasion airport art, Again, a series of acquisitions might represent a decade's fieldwork documenting social experience as expressed in the varieties of clothing and jewellery styles, tents and camel trappings from various Middle Eastern countries, or in the developing preferences in personal adornment and dress from Papua New Guinea. Particularly interesting are a series of collections which continue to document the evolution of ceremony and of material forms for which the Department already possesses early (if not the earliest) collections formed after the first contact with Europeans.The importance of these acquisitions extends beyond the objects themselves. They come to the Museum with documentation of the social context, ideally inc luding photographic records. Such acquisitions have multiple purposes. Most significantly they document for future change. Most people think of the cultures represented in the collection in terms of the absence of advanced technology. in fact. traditional practices draw on a continuing wealth of technological ingenu iry Limited resources and ecological constraints are often overcome by personal skills that would be regarded as exceptional in the West. Of growing interest is the way in which much of what we might see as disposable is, elsewhere, recycled and reused.With the independence of much of Asia and Africa after 1945. it was assumed that economic progress would rapidly lead to the disappearance or assimilation of many small-scale societies. Therefore, it was felt that the Museum should acquire materials representing people whose art or material culture, ritual or political structures were on the point of irrevocable change. This attitude altered with the realisation that marginal communities can survive and adopt in spite of partial integration into a notoriously fickle world economy. Since the seventeenth century, with the advent of trading companies exporting manufactured textiles to North America and Asia, the importation of cheap goods has often contributed to the destruction of local skills and indigenous markets. On the one hand modem imported goods may be used in on everyday setting, while on the other hand. other traditional objects may still be required for ritually significant events. Within this context trade and exchange attitudes are inverted. What are utilitarian objects to a Westerner may be prizedobjects in other cultures- when trans- formed by local ingenuity-principally for aesthetic value. in the same way, the West imports goods form other peoples and in certain circumstances categorises the m as ‘art'.Collections act as an ever-expanding database, not merely for scholars and anthropologists, but for people involved in a whole range of educational and art is tic purposes. These include schools and universities as well as colleges of art and design. The provision of information about non-Western aesthetics and techniques, not just for designers and artists but for all visitors, is a growing responsibility for a Department whose own context is an increasingly multicultural European society.Questions 1-6Do the following statements agree with the information given in Reading Passage 1?In boxes 1-6 on your answer sheet writeTRUE if the statement is true according to the passageFALSE if the statement is false according to the passageNOT GIVEN if the information is not given in the passageExample AnswerThe Department of Ethnography FALSEreplaced the Department of Antiquitiesat the British Museum.1 The twentieth-century collections come mainly from mainstream societies such as the US and Europe.2 The Department of Ethnography focuses mainly on modern societies.3 The Department concentrates on collecting single unrelated objects of great value.4 The textile collection of the Department of Ethnography is the largest in the world.5 Traditional societies are highly inventive in terms of technology.6 Many small-scale societies have survived and adapted in spite of predictions to the contrary.Questions 7-12Some of the exhibits at the Department of Ethnography are listed below (Questions 7-12).The writer gives these exhibits as examples of different collection types.Match each exhibit with the collection type with which it is associated in Reading Passage 1.Write the appropriate letters in boxes 7-12 on your answer sheet.NB You may use any collection type more than once.Collection TypesAT A rtefact T ypesEC E volution of C eremonyFA F ield A ssemblagesSE S ocial E xperienceTS T echnical S eriesExample AnswerBoats AT7 Bolivian textiles8 Indian coracles9 airport art10 Arctic kayaks11 necessities of life of an Arabian farmer12 tents from the Middle EastREADING PASSAGE 2You should spend about 20 minutes on Questions 13-25 which are based on Reading Passage 2 on the following pages.Questions 13-15Reading Passage 2 has six sections A-F.Choose the most suitable headings for sections A, B and D from the list of headings below.Write the appropriate numbers i-vii in boxes 13-15 on your answer sheet.List of Headingsi Amazonia as unable to sustain complexsocietiesii The role of recent technology in ecologicalresearch in Amazoniaiii The hostility of the indigenous populationto North American influencesiv Recent evidencev Early research among the Indian Amazonsvi The influence of prehistoric inhabitants onAmazonian natural historyvii The great difficulty of changing localattitudes and practices13 Section A14 Section BExample AnswerSection C iv15 Section DSecrets of the ForestA In 1942 Allan R Holmberg, a doctoral student in anthropology from Yale University, USA, ventured deep into the jungle of Bolivian Amazonia and searched out an isolated band of Siriono Indians. The Siriono, Holmberg later wrote, led a "strikingly backward" existence. Their villages were little more than clusters of thatched huts. Life itself was a perpetual and punishing search for food: some families grew manioc and other starchy crops in small garden plots cleared from the forest, while other members of the tribe scoured the country for small game and promising fish holes. When local resources became depleted, the tribe moved on. As for technology, Holmberg noted, the Siriono "may be classified among the most handicapped peoples of the world". Other than bows, arrows and crude digging sticks, the only tools the Siriono seemed to possess were "two machetes worn to the size of pocket-knives".B Although the lives of the Siriono have changed in the intervening decades, the image of them as Stone Age relics has endured. Indeed, in many respects the Siriono epitomize the popular conception of life in Amazonia. To casual observers, as well as to influential natural scientists and regional planners, the luxuriant forests of Amazonia seem ageless, unconquerable,a habitat totally hostile to human civilization. The apparent simplicity of Indian ways of life has been judged an evolutionary adaptation to forest ecology, living proof that Amazonia could not - and cannot - sustain a more complex society. Archaeological traces of far more elaborate cultures have been dismissed as the ruins of invaders from outside the region, abandoned to decay in the uncompromising tropical environment.C The popular conception of Amazonia and its native residents would be enormously consequential if it were true. But the human history of Amazonia in the past 11,000 years betrays that view as myth. Evidence gathered in recent years from anthropology and archaeology indicates that the region has supported a series of indigenous cultures for eleven thousand years; an extensive network of complex societies - some with populations perhaps as large as 100,000 - thrived there for more than 1,000 years before the arrival of Europeans. (Indeed, some contemporary tribes, including the Siriono, still live among the earthworks of earlier cultures.) Far from being evolutionarily retarded, prehistoric Amazonian people developed technologies and cultures that were advanced for their time. If the lives of Indians today seem "primitive", the appearance is not the result of some environmental adaptation or ecological barrier; rather it is a comparatively recent adaptation to centuries of economic and political pressure. Investigators who argue otherwise have unwittingly projected the present onto the past.D The evidence for a revised view of Amazonia will take many people by surprise. Ecologists have assumed that tropical ecosystems were shaped entirely by natural forces and they have focused their research on habitats they believe have escaped human influence. But as the University of Florida ecologist, Peter Feinsinger, has noted, an approac h that leaves people out of the equation is no longer tenable. The archaeological evidence shows that the natural history of Amazonia is to a surprising extent tied to the activities of its prehistoric inhabitants.E The realization comes none too soon. In June 1992 political and environmental leaders from across the world met in Rio de Janeiro to discuss how developing countries can advance their economies without destroying their natural resources. The challenge is especially difficult in Amazonia. Because the tropical forest has been depicted as ecologically unfit forlarge-scale human occupation, some environmentalists have opposed development of any kind. Ironically, one major casualty of that extreme position has been the environment itself. While policy makers struggle to define and implement appropriate legislation, development of the most destructive kind has continued apace over vast areas.F The other major casualty of the "naturalism" of environmental scientists has been the indigenous Amazonians, whose habits of hunting, fishing, and slash-and-burn cultivation often have been represented as harmful to the habitat. In the clash between environmentalists and developers, the Indians, whose presence is in fact crucial to the survival of the forest, have suffered the most. The new understanding of the pre-history of Amazonia, however, points toward a middle ground. Archaeology makes clear that with judicious management selected parts of the region could support more people than anyone thought before. The long-buried past, it seems, offers hope for the future.Questions 16-21Do the following statements agree with the views of the writer in Reading Passage 2?In boxes 16-21 on your answer sheet writeYES if the statement agrees with the views of the writerNO if the statement contradicts the views of the writerNOT GIVEN if it is impossible to say what the writer thinks about thisExample AnswerThe prehistoric inhaditants of NOAmazonia were relatively backward intechnological terms.16 The reason for the simplicity of the Indian way of life is that Amazonia has always been unable to support a more complex society.17 There is a crucial popular misconception about the human history of Amazonia.18 There are lessons to be learned from similar ecosystems in other parts of the world.19 Most ecologists were aware that the areas of Amazonia they were working in had been shaped by human settlement.20 The indigenous Amazonian Indians are necessary to the well-being of the forest.21 It would be possible for certain parts of Amazonia to support a higher population.Questions 22-25Choose the appropriate letters A-D and write them in boxes 22-25 on your answer sheet.22 In 1942 the US anthropology student concluded that the SirionoA were unusually aggressive and cruel.B had had their way of life destroyed by invaders.C were an extremely primitive society.D had only recently made permanent settlements.23 The author believes recent discoveries of the remains of complex societies in AmazoniaA are evidence of early indigenous communities.B are the remains of settlements by invaders.C are the ruins of communities established since the European invasions.D show the region has only relatively recently been covered by forest.24 The assumption that the tropical ecosystem of Amazonia has been created solely by natural forcesA has often been questioned by ecologists in the past.B has been shown to be incorrect by recent research.C was made by Peter Feinsinger and other ecologists.D has led to some fruitful discoveries.25 The application of our new insights into the Amazonian past wouldA warn us against allowing any development at all.B cause further suffering to the Indian communities.C change present policies on development in the region.D reduce the amount of hunting, fishing, and 'slash-and-burn'.READING PASSAGE 3You should spend about 20 minutes on Questions 26-40 which are based on Reading Passage 3 below.HIGHS & LOWSHormone levels - and hence our moods - may be affected by the weather. Gloomy weather can cause depression, but sun- shine appears to raise the spirits. In Britain, for example, the dull weather of winter drastically cuts down the amount of sunlight that is experienced which strongly affects some people. They become so depressed and lacking in energy that their work and social life are affected. This condition has been given the name SAD (Seasonal Affective Disorder), Sufferers can fight back by making the most of any sunlight in winter and by spending a few hours each day under special, full-spectrum lamps. These provide more ultraviolet and blue- green light than ordinary fluorescent and tungsten lights. Some Russian scientists claim that children learn better after being exposed to ultraviolet light. In warm countries, hours of work are of ten arranged so that workers can take a break, or even a siesta, during the hottest part of the day. Scientists are working to discover the links between the weather and human beings' moods and performance.It is generally believed that tempers grow shorter in hot, muggy weather. There is no doubt that 'crimes against the person' rise in the summer, when the weather is hotter and fall in the winter when the weather is colder. Research in the United States has shown a relation- ship between temperature and street riots. The frequency of riots rises dramatically as the weather gets warmer, hitting a peak around 27-30~C. But is this effect really due to a mood change caused by the heat? Some scientists argue that trouble starts more Often in hot weather merely because there are more people in the street when the weather is good.Psychologists have also studied how being cold affects performance. Re- searchers compared divers working in icy cold water at 5~C with others in water at 20~C (about swimming pool temperature). The colder water made the divers worse at simple arithmetic and other mental tasks. But significantly, their performance was impaired as soon as they were put into the cold water - before their bodies had time to cool down. This suggests that the low temperature did not slow down mental functioning directly, but the feeling of cold distracted the divers from their tasks.Psychologists have conducted studies showing that people become less secptical and more optimistic when the weather is sunny. However, this apparently does not just depend on the temperature. An American psychologist studied customers in a temperature- controlled restaurant. They gave bigger tips when the sun was shining and smaller tips when it wasn't, even though the temperature in the restaurant was the same. Alink between weather and mood is made believable by the evidence for a connection between behaviour and the length of the daylight hours. This in turn might involve the level of a hormone called melatonin, produced in the pineal gland in the brain. The amount of melatonin falls with greater exposure to daylight. Research shows that melatonin plays an important part in the seasonal behaviour of certain animals. For example, food consumption of stags increases during the winter, reaching a peak in February/ March. It falls again to a low point in May, then rises to a peak in September, before dropping to another minimum in November. These changes seem to be triggered by varying melatonin levels.In the laboratory, hamsters put on more weight when the nights are getting shorter and their melatonin levels are falling. On the other hand, if they are given injections of melatonin, they will stop eating altogether. It seems that time cues provided by the changing lengths of day and night trigger changes in animals' behaviour - changes that are needed to cope with the cycle of the seasons. People's moods too, have been shown to react to the length of the day- light hours. Sceptics might say that longer exposure to sunshine puts people in a better mood because they associate it with the happy feelings of holidays and freedom from responsibility, However, the belief that rain and murky weather make people more unhappy is borne out by a study in Belgium, which showed that a telephone counselling service gets more telephone calls from people with suicidal feelings when it rains.When there is a thunderstorm brewing, some people complain of the air being 'heavy' and of feeling irritable, moody and on edge. They may be reacting to the fact that the air can become slightly positively c harged when large thunderclouds are generating the intense electrical fields that cause lightning flashes. The positive charge increases the levels of serotonin (a chemical involved in sending signals in the nervous system). High levels of serotonin in certain areas of the nervous system make people more active and reactive and, possibly, more aggressive. When certain winds are blowing, such as the Mistral in southern France and the Fshn in southern Germany, mood can be affected - and the number of traffic accidents rises. It may be significant that the concentration of positively charged particles is greater than normal in these winds. In the United Kingdom, 400,000 ionizers are sold every year. These small machines raise the number of negative ions in the air in a room. Many people claim they feel better in negatively charged air.Questions 26-28Choose the appropriate letters A-D and write them in boxes 26-28 on your answer sheet.26 Why did the divers perform less well in colder conditions?A They were less able to concentrate.B Their body temperature fell too quickly.C Their mental functions were immediately affected by the cold.D They were used to swimming pool conditions.27 The number of daylight hoursA affects the performance of workers in restaurants.B influences animal feeding habits.C makes animals like hamsters more active.D prepares humans for having greater leisure time.28 Human irritability may be influenced byA how nervous and aggressive people are.B reaction to certain weather phenomena.C the number of ions being generated by machines.D the attitude of people to thunderstorms.Questions 29-34Do the following statements agree with the information in Reading Passage 3?In boxes 29-34 on your answer sheet writeTRUE if the statement is true according to the passageFALSE if the statement is false according to the passageNOT GIVEN if the information is not given in the passage29 Seasonal Affective Disorder is disrupting children's education in Russia.30 Serotonin is an essential cause of human aggression.31 Scientific evidence links 'happy associations with weather' to human mood.32 A link between depression and the time of year has been established.33 Melatonin levels increase at certain times of the year.34 Positively charged ions can influence eating habits.Questions 35-37According to the text which THREE of the following conditions have been scientifically proved to have a psychological effect on humans?Choose THREE letters A-G and write them in boxes 35-37 on your answer sheet,A lack of negative ionsB rainy weatherC food consumptionD high serotonin levelsE sunny weatherF freedom from worryG lack of counselling facilitiesQuestions 38-40Complete each of the following statements with the best ending from the box below.Write the appropriate letters A-G in boxes 38-40 on your answer sheet.38 It has been established that social tension increases significantly in the United States I during ...39 Research has shown that a hamster's bodyweight increases according to its exposure to...40 Animals cope with changing weather and food availability because they are influenced by...A daylightB hot weatherC melatoninD moderate temperaturesE poor co-ordinationF time cuesG impaired performanceWritingWRITING TASK1You should spend about 20 minutes on this task.The charts below show the levels of participation in education and science in developing and industrialised countries in 1980 and 1990.Write a report for a university lecturer describing the information shown below.You should write at least 150 words._________________________________________________________________ _________________________________________________________________ _________________________________________________________________。

7s管理知识30问

7s管理知识30问 7S Management Knowledge 30 Questions. English Answer:1. What are the 7Ss of management?> Shared Values.> Strategy.> Structure.> Systems.> Staff.> Style.> Skills.2. How do the 7Ss interact with each other?> The 7Ss are interconnected and interdependent,forming a holistic view of an organization.3. What is the role of shared values in an organization?> Shared values guide the organization's behavior and decision-making.4. How does strategy influence the other 6Ss?> Strategy sets the direction for the organization and aligns the other 6Ss.5. What is the purpose of organizational structure?> Structure defines the relationships andresponsibilities within the organization.6. How do systems support organizational goals?> Systems provide the processes and procedures to achieve organizational objectives.7. What is the importance of staff in an organization?> Staff are the human resources that carry out the organization's activities.8. How does leadership style affect organizational performance?> Leadership style influences the way the organization is managed and employees are motivated.9. Why are skills essential for organizational success?> Skills enable the organization to execute its strategy and achieve its goals.10. How can the 7Ss be used to improve organizational performance?> By aligning and optimizing the 7Ss, organizations can enhance their effectiveness and efficiency.11. What are the benefits of using the 7S framework?> The 7S framework provides a comprehensive understanding of an organization and facilitates change management.12. How can organizations assess their 7Ss?> Organizations can use various tools and techniques to evaluate their 7Ss.13. What are some common challenges in implementing the 7Ss?> Challenges include resistance to change, lack of alignment, and resource constraints.14. How can organizations overcome challenges inimplementing the 7Ss?> Organizations can overcome challenges through communication, stakeholder involvement, and gradual implementation.15. What are the implications of the 7Ss for organizational culture?> The 7Ss shape and reflect the organization's culture.16. How can the 7Ss be used to diagnose organizational problems?> By examining the alignment and effectiveness of the7Ss, organizations can identify areas for improvement.17. What is the relationship between the 7Ss and organizational change?> The 7Ss provide a framework for understanding and managing organizational change.18. How can the 7Ss be used to create a sustainable organization?> By integrating environmental and social considerations into the 7Ss, organizations can promote sustainability.19. What are some best practices for implementing the 7Ss effectively?> Best practices include stakeholder involvement, continuous monitoring, and flexibility.20. How can organizations leverage technology to support the 7Ss?> Technology can enhance communication, collaboration, and data analysis for the 7Ss.21. What is the role of leadership in implementing the 7Ss?> Leadership plays a crucial role in communicating, facilitating, and sustaining the 7Ss.22. How can the 7Ss be used to promote innovation in an organization?> By fostering a culture of experimentation, risk-taking, and cross-functional collaboration, the 7Ss can support innovation.23. What are some ethical considerations in implementing the 7Ss?> Organizations must ensure that the 7Ss are implemented in an ethical and responsible manner.24. How can the 7Ss be used to build a learning organization?> By creating a culture of continuous learning, sharing, and knowledge management, the 7Ss can foster a learningorganization.25. What is the impact of globalization on the 7Ss?> Globalization influences the 7Ss by increasing interconnectedness, competition, and cultural diversity.26. How can organizations use the 7Ss to adapt to a rapidly changing environment?> By aligning the 7Ss with the external environment, organizations can enhance their adaptability.27. What are the key performance indicators for measuring the effectiveness of the 7Ss?> KPIs include employee satisfaction, customer satisfaction, financial performance, and innovation metrics.28. How can organizations create a balanced and aligned 7Ss?> By considering the interdependencies and trade-offs between the 7Ss, organizations can achieve balance and alignment.29. What is the future of the 7S framework?> The 7S framework continues to evolve and adapt to changes in the business landscape.30. How can organizations leverage the 7Ss to gain a competitive advantage?> By aligning and optimizing the 7Ss, organizations can differentiate themselves and enhance their competitiveness.中文回答：1. 7s管理知识包括哪些方面？> 战略（Strategy）。

nosql数据库的base原则

nosql数据库的base原则NoSQL数据库的base原则随着互联网的快速发展和大数据的普及应用，传统的关系型数据库在处理海量数据时面临着很多问题，比如扩展性差、性能低下等。

为了解决这些问题，NoSQL数据库应运而生。

NoSQL（Not Only SQL）数据库是一种非关系型的数据库管理系统，以其高性能、高可扩展性和灵活性而备受关注。

在设计和使用NoSQL数据库时，有一些基本原则需要遵循，以确保数据库的高效运行和可靠性。

1. 水平扩展性（Horizontal Scalability）水平扩展性是NoSQL数据库的一项重要原则。

传统的关系型数据库通常采用垂直扩展方式，即通过增加硬件资源来提升性能，但这种方式存在着成本高、扩展性差等问题。

而NoSQL数据库通过将数据分片存储在多个节点上，实现了水平扩展。

这种方式可以根据需求随时增减节点，并且可以利用分布式计算和存储的优势，提高系统的吞吐量和性能。

2. 高可用性（High Availability）高可用性是NoSQL数据库的另一个重要原则。

在分布式环境下，节点的故障是不可避免的。

为了保证系统的正常运行，NoSQL数据库需要具备高可用性。

通过数据的冗余备份和自动故障转移，可以在节点故障时保持系统的可用性。

此外，还可以通过数据的副本和数据同步机制，实现数据的持久性和一致性，确保数据不会丢失和损坏。

3. 灵活的数据模型（Flexible Data Model）NoSQL数据库采用了灵活的数据模型，与传统的关系型数据库相比，不再需要事先定义表结构和字段。

这使得NoSQL数据库能够处理半结构化和非结构化的数据，适应不同类型和格式的数据存储需求。

此外，NoSQL数据库还支持动态的数据模型和模式演化，可以随时根据业务需求进行扩展和修改，提高了开发的灵活性和效率。

4. 分布式计算和存储（Distributed Computing and Storage）NoSQL数据库基于分布式计算和存储的原理，通过将数据分散存储在多个节点上，实现了数据的并行处理和分布式计算。

Spring考试试卷(有答案)

Spring考试试卷（题库）下列关于✌的说法错误的是（）。

✌．✌将散落在系统中的❽方面❾代码集中实现．✌有助于提高系统的可维护性．✌已经表现出了将要替代面向对象的趋势．✌是一种设计模式， ☐❒♓⏹♑为其提供了一种实现在 ☟整合时，事务隔离级别是由（）实现的。

✌．☺♋❖♋应用程序 ．☟♓♌♏❒⏹♋♦♏ ．数据库系统 ．☺ 驱动程序下列（）不是 ☐❒♓⏹♑的依赖注入方式。

【选两项】✌．♦♏♦♦♏❒注入．♑♏♦♦♏❒注入 ．接口注入 ．构造注入在 ☐❒♓⏹♑框架中，面向方面编程（✌）的目标在于（）。

✌．编写程序时不用关心其依赖组件的实现．将程序中涉及的公用问题集中解决．封装☺ 访训数据库的代码，简化数据访训层的得复性代码．实现画面的“无刷新❾关于 ☐❒♓⏹♑ 与 ☟♓♌♏❒⏹♋♦♏集成，下列说法错误的是（）。

✌． ☐❒♓⏹♑提供了☟♓♌♏❒⏹♋♦♏♋☐◆☐☐☐❒♦类来简化☟♓♌♏❒⏹♋♦♏的使用．在 ☐❒♓⏹♑配置文件中，可以通过 ☐❒♓⏹♑提供的☹☐♍♋●♏♦♦♓☐⏹☞♋♍♦☐❒⍓♏♋⏹来获得 ♏♦♦♓☐⏹☞♋♍♦☐❒⍓的实例．通过集成 ☐❒♓⏹♑和☟♓♌♏❒⏹♋♦♏，用 ☐❒♓⏹♑管理程序的依赖关系，将 ♏♦♦♓☐⏹☞♋♍♦☐❒⍓注入到 ♋♦♋☐◆❒♍♏中．通过 ☐❒♓⏹♑，可以在 ♓层代码中无需直接实例化 ✌类，而是通过注入得到在 ☐❒♓⏹♑中，下列关于依赖注入的说法，正确的是（）。

✌．依赖注入的目标是在代码之外管理程序组建间的依赖关系（组件？组建？）．依赖注入即❽面向接口❾的编程．依赖注入是面向对象技术的替代品．依赖注入的使用会增大程序的规模下列关于 ☐❒♓⏹♑的说法错误的是（）。

✌． ☐❒♓⏹♑是一个轻量级☺✌✞✌ ☜☜的框架集合 ． ☐❒♓⏹♑是❽依赖注入❾模式的实现．使用 ☐❒♓⏹♑可以实现声明事务 ． ☐❒♓⏹♑提供了✌方式的日志系统在 ☐❒♓⏹♑ 中，配置☟♓♌♏❒⏹♋♦♏ 事务管理器（☟♓♌♏❒⏹♋♦♏ ❆❒♋⏹♦♋♍♦♓☐⏹♋⏹♋♑♏❒）时，需要注入的属性名称是（）。

应用分支界限算法的原理

应用分支界限算法的原理1. 算法概述分支界限算法（Branch and Bound）是一种常用于解决优化问题的算法。

它通过将问题分解为子问题，并对每个子问题设置上界，从而有效地减少搜索空间。

本文将介绍应用分支界限算法的原理，并讨论其在实际应用中的一些重要应用。

2. 算法原理分支界限算法的基本思想是通过不断划分问题的解空间来找到最优解。

具体而言，该算法通过对问题进行分解，形成一个解空间树，然后根据问题的约束条件和目标函数，在解空间树的每一层使用界限函数来对解进行评估，并决定是否继续搜索该分支或剪枝。

2.1 解空间树解空间树是分支界限算法的重要概念，它代表了问题的解空间。

解空间树的根节点表示问题的初始状态，树的每一层都代表了问题的一个解的可能性。

算法通过不断地扩展解空间树的分支，并采用剪枝策略来减少搜索空间。

2.2 上界与界限函数在分支界限算法中，上界函数用于估计问题的最优解的上界，从而在搜索过程中可以及时进行剪枝。

界限函数则用于对解进行评估，并决定是否继续搜索该分支。

2.3 剪枝策略分支界限算法通过设置剪枝策略来减少搜索空间，提高算法效率。

常用的剪枝策略包括确定界限函数的下界和上界、使用排序策略优化搜索顺序、使用限界虚拟节点等方法。

3. 应用领域分支界限算法被广泛应用于各个领域的优化问题。

下面介绍几个典型的应用领域。

3.1 旅行商问题旅行商问题是一个经典的组合优化问题，其目标是找到一条路径，使得旅行商能够经过每个城市恰好一次，并返回出发地，使得路径的长度最小。

分支界限算法可用于找到具有全局最小路径的解。

3.2 背包问题背包问题是求解如何选择有限物品装入背包，使得装入的物品价值最大化的问题。

分支界限算法可以通过确定上界函数来剪去不可能的解，从而高效地搜索到最优解。

3.3 任务调度问题任务调度问题是指如何合理地安排任务的执行顺序和分配资源的问题。

分支界限算法可以通过设置界限函数，确定任务的执行顺序和资源分配的约束条件，从而找到最优的任务调度方案。

IBM Cognos Transformer V11.0 用户指南说明书

Dimensional Modeling Workflow................................................................................................................. 1 Analyzing Your Requirements and Source Data.................................................................................... 1 Preprocessing Your ...................................................................................................................... 2 Building a Prototype............................................................................................................................... 4 Refining Your Model............................................................................................................................... 5 Diagnose and Resolve Any Design Problems........................................................................................ 6

有关科技革命的英语作文

The advent of the technological revolution has ushered in a new era of human civilization, profoundly altering the way we live, work, and interact with one another. This transformative period, marked by rapid advancements in fields such as artificial intelligence, the internet of things, and biotechnology, has been nothing short of a renaissance for the modern world.In the realm of communication, the evolution from traditional letters to emails and instant messaging has been a testament to the power of technology. People can now connect with loved ones across the globe with just a few clicks, a stark contrast to the days when a letter could take weeks to reach its destination. The convenience and speed of digital communication have not only brought people closer but have also revolutionized the business world, enabling faster decisionmaking and more efficient collaboration.The impact of technology on education has been equally transformative. With the rise of online learning platforms, students have access to a wealth of knowledge at their fingertips. This democratization of education has allowed individuals from diverse backgrounds to pursue their interests and acquire new skills without the constraints of geographical boundaries or financial limitations. Moreover, the integration of virtual reality and augmented reality in educational settings has provided immersive learning experiences that were once unimaginable.Healthcare, too, has seen a revolution with the advent of advanced diagnostic tools, telemedicine, and personalized medicine. The ability toanalyze vast amounts of data has led to more accurate diagnoses and treatment plans, improving patient outcomes. Telemedicine has made healthcare more accessible, particularly for those living in remote areas, by allowing virtual consultations with medical professionals. The promise of personalized medicine, driven by genomics, holds the potential to tailor treatments to an individuals unique genetic makeup, thereby increasing the efficacy of medical interventions.However, the technological revolution has not been without its challenges. The rapid pace of change has left some individuals feeling overwhelmed and struggling to keep up. The digital divide, where access to technology is unequally distributed, has exacerbated social and economic disparities. Furthermore, concerns about privacy and data security have become more pressing as our lives become increasingly intertwined with digital platforms.Despite these challenges, the benefits of the technological revolution are undeniable. The development of renewable energy sources, such as solar and wind power, has been a significant step towards a more sustainable future. These technologies have the potential to reduce our reliance on fossil fuels, mitigating the impact of climate change and preserving the environment for future generations.In the realm of transportation, electric vehicles and selfdriving cars are reshaping our cities and reducing our carbon footprint. The efficiency and convenience of these technologies promise to revolutionize urban mobility, making our cities more livable and our air cleaner.The fusion of technology and creativity has also given rise to new forms of art and entertainment. Digital art, virtual reality experiences, and interactive installations have expanded the boundaries of artistic expression, offering audiences unique and immersive experiences.In conclusion, the technological revolution has brought about profound changes in various aspects of our lives. While it presents challenges that must be addressed, the potential benefits are immense. As we continue to navigate this new landscape, it is crucial to harness the power of technology responsibly, ensuring that its advancements serve to improve the quality of life for all.。

implementation realization 编程

implementation realization 编程
Implementation 和Realization 在编程中都有“实现”的意思，但它们的使用场景略有不同。

Implementation 通常指的是具体的实现过程、代码或方法。

它强调将一个设计或规范转化为可执行的代码。

例如，你可以说“我们正在实施一个新的算法来提高性能”。

Realization 更侧重于实现的结果或完成的状态。

它表示将一个概念、想法或目标转化为实际的存在或实现。

例如，你可以说“我们已经实现了项目的主要目标”。

在编程中，这两个词通常可以互换使用，但Implementation 更常用于描述具体的编码工作和技术实现细节，而 Realization 更常用于强调完成的状态或达成的结果。

例如，在软件开发过程中，你可能会说：
- “我们正在实施一个新的用户界面设计。

”
- “通过这个实现，我们成功地提高了系统的性能。

”
总的来说，Implementation 和 Realization 在编程中都是表示“实现”的概念，但Implementation 更侧重于过程和技术细节，而 Realization 更侧重于结果和完成状态。

希望这个解释对你有所帮助！如果你有任何其他问题，请随时提问。

react高级面试题

1. 请解释React中的虚拟DOM（Virtual DOM）以及它的作用。

2. 请解释React中的组件生命周期方法，并列举它们的执行顺序。

3. 请解释React中的state和props，并说明它们之间的区别。

4. 如何在React中实现条件渲染？
5. 请解释React中的事件处理，并给出一个示例。

6. 如何在React中实现列表渲染？
7. 请解释React中的高阶组件（Higher-Order Components），并给出一个示例。

8. 如何在React中实现表单处理？
9. 请解释React中的受控组件和非受控组件，并说明它们之间的区别。

10. 如何在React中实现错误边界（Error Boundaries）？
11. 请解释React中的单向数据流（One-Way Data Flow）以及它的优点。

12. 如何在React中实现路由？
13. 请解释React中的合成事件（Synthetic Events）以及它们与原生事件的区别。

14. 如何在React中实现动画？
15. 请解释React中的服务器端渲染（Server-Side Rendering）以及它的优点。

16. 如何在React中实现代码分割（Code Splitting）？
17. 请解释React中的Hooks，并列举一些常用的Hooks。

18. 如何在React中实现懒加载（Lazy Loading）？
19. 请解释React中的Context API，并给出一个示例。

20. 如何在React中实现单元测试？。

allegro中的约束规则

Allegro中的约束规则1. 引言Allegro是一种常用的约束编程语言，用于解决各种复杂的优化问题。

约束规则是Allegro中的核心概念，它定义了问题的约束条件和限制。

本文将深入探讨Allegro中的约束规则，并介绍其在问题求解中的应用。

2. 约束规则的定义约束规则是一种逻辑表达式，用于描述问题的约束条件和限制。

它由一系列约束项组成，每个约束项由一个或多个变量和一个约束关系组成。

约束关系可以是等式、不等式、集合关系等。

通过将约束规则与变量绑定，可以限制变量的取值范围，从而满足问题的约束条件。

3. 约束规则的语法Allegro中的约束规则采用一种类似于逻辑编程语言的语法。

它包括变量声明、约束项和约束关系等元素。

以下是约束规则的语法示例：var X: int;var Y: int;constraint X > Y;在上述示例中，我们声明了两个整数变量X和Y，并添加了一个约束项，要求X大于Y。

4. 约束规则的应用约束规则在Allegro中被广泛应用于各种问题的求解。

它可以用于解决数学问题、逻辑问题、排程问题等。

以下是一些常见问题的约束规则应用示例：4.1 数独问题数独是一种经典的逻辑推理游戏，玩家需要根据已知的数字填充空白格子，使得每一行、每一列和每一个九宫格内的数字都满足1到9的要求。

数独问题可以使用约束规则来求解。

以下是数独问题的约束规则示例： - 每一行的数字不能重复。

- 每一列的数字不能重复。

- 每一个九宫格内的数字不能重复。

4.2 旅行商问题旅行商问题是一个经典的组合优化问题，目标是找到一条路径，使得旅行商能够经过所有城市并返回起始城市，同时使得路径的总长度最小。

旅行商问题可以使用约束规则来求解。

以下是旅行商问题的约束规则示例： - 每个城市只能访问一次。

- 路径的起始城市和终止城市必须相同。

- 路径的总长度需要最小化。

4.3 排程问题排程问题是一个经典的调度问题，目标是合理安排任务的执行顺序和时间，以最大程度地提高资源利用率和任务完成率。

组件库实现国际化的方法-概述说明以及解释

组件库实现国际化的方法-概述说明以及解释1.引言1.1 概述随着全球化的发展，越来越多的公司和组织拥有跨国业务和用户群体。

在这种情况下，如何有效地对不同地区和语言的用户提供一致的用户体验成为了一个重要的挑战。

组件库作为前端开发中常用的工具之一，扮演着统一UI风格和功能的角色，对于实现跨语言、跨地区的国际化起着至关重要的作用。

本文将探讨组件库实现国际化的方法，从组件库的概念入手，分析国际化对于组件库的重要性，以及国际化实现的基本原理。

通过对这些内容的深入探讨，希望可以为开发者提供一些有益的参考，帮助他们更好地应对国际化的挑战，提升软件的用户体验和市场竞争力。

文章结构部分的内容：文章结构是指本文所呈现的内容在逻辑上的组织和展示方式。

对于本文"组件库实现国际化的方法"，文章结构按照以下方式展开：1. 引言部分：- 1.1 概述：介绍本文的主题和背景，引出国际化在组件库中的重要性。

- 1.2 文章结构：解释文章的组织结构，包括每个部分的内容和逻辑关系。

- 1.3 目的：说明本文的写作目的和期望达到的效果。

2. 正文部分：- 2.1 什么是组件库：介绍组件库的定义和作用，阐述组件库在前端开发中的重要性。

- 2.2 国际化的重要性：讨论国际化对于产品的意义和价值，说明国际化在跨文化背景下的必要性。

- 2.3 国际化实现的基本原理：详细介绍组件库实现国际化的方法和步骤，包括语言切换、文本翻译等技术方案。

3. 结论部分：- 3.1 总结：总结本文的主要内容和结论，强调国际化在组件库中的重要性。

- 3.2 实践意义：探讨组件库国际化的实际应用和优势，为开发者提供具体指导和建议。

- 3.3 展望：展望未来组件库国际化的发展趋势和挑战，为读者提供思考和学习的方向。

通过以上的文章结构，读者可以清晰地了解本文的内容安排和逻辑展示，帮助他们更好地理解和吸收所呈现的知识。

1.3 目的本文旨在探讨如何在组件库中实现国际化，通过介绍国际化的基本概念和原理，帮助读者了解国际化在组件库开发中的重要性以及具体实现的方法。

依赖传递问题

依赖传递问题"依赖传递问题"这个术语在软件开发和计算机科学领域经常被使用，通常指的是一个组件、模块、或函数依赖于另一个组件、模块、或函数的输出或功能。

依赖传递问题可能导致一系列的挑战和不良影响，具体取决于上下文和程序的复杂性。

以下是一些常见的依赖传递问题及其可能的影响：1.紧耦合（Tight Coupling）：如果组件之间的依赖关系过于紧密，一个组件的修改可能会导致其他相关组件的改变。

这增加了系统的脆弱性，使得维护和更新变得更加困难。

2.难以测试：当一个组件依赖于其他组件时，测试变得更加复杂。

因为修改一个组件可能需要同时修改其依赖的组件，这可能导致测试用例的频繁更新。

3.可维护性下降：依赖传递问题会增加代码的复杂性，降低可读性和可维护性。

如果一个组件的改变需要涉及多个地方的修改，就会使得代码的演进变得困难。

4.难以并行开发：当多个团队或开发者同时工作于一个项目时，依赖传递问题可能导致合并冲突，因为一个组件的修改可能会与其他人的修改发生冲突。

5.性能问题：过多的依赖关系可能导致性能下降，因为在执行时需要更多的上下文切换、数据传输等操作。

为了解决依赖传递问题，通常会采取以下策略：1.模块化设计：将系统划分为相互独立的模块，每个模块只负责特定的功能。

通过定义清晰的接口，减少模块之间的直接依赖。

2.依赖注入（Dependency Injection）：通过将依赖项从组件的内部移到外部，以减少组件之间的直接耦合。

这样做可以更容易地替换、更新或测试组件。

3.使用接口和抽象类：使用接口和抽象类定义组件之间的契约，而不是依赖具体的实现。

这样，可以更轻松地替换实现而不影响其他组件。

4.事件驱动架构：使用事件和消息传递来解耦组件。

当一个组件发生变化时，通过事件通知其他组件，而不是直接调用它们的方法。

5.分层架构：将系统分为不同的层次，确保底层层次只依赖于更底层的层次，而不依赖于更高层次。

这有助于维持清晰的层次结构和减少耦合。

1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。

Implementing Global Constraints asGraphs of Elementary ConstraintsDávid HanákBudapest University of Technology and EconomicsDept.of Computer Science and Information Theorydhanak@cs.bme.huAbstract.Global constraints are cardinal concepts of CLP(FD),a constraint programminglanguage.They are means toﬁnd a set of integers that satisfy certain relations.The factthat deﬁning global constraints often requires the knowledge of a speciﬁcation languagemakes sharing constraints between scientists and programmers diﬃcult.Nicolas Beldiceanupresented a theory that could solve this problem,because it depicts global constraints asgraphs:an abstraction that everyone understands.The abstract description language deﬁned by the theory may also be interpreted by a com-puter program.This paper deals with the problematic issues of putting the theory intopractice by implementing such a program.It introduces a concrete syntax of the languageand presents three programs understanding that syntax.These case studies represent twodiﬀerent approaches of propagation.One of these oﬀers exhausting pruning with poor eﬃ-ciency,the other,yet unﬁnished attempt provides a better alternative at the cost of beinga lot more complicated.1IntroductionConstraint Logic Programming(CLP,also referred to as Constraint Programming,CP)[1]is a family of logic programming languages,where a problem is deﬁned in terms of correlations between unknown values,and a solution is a set of values which satisfy the correlations.In other words, the correlations constrain the set of acceptable values,hence the name.A member of this family is CLP(FD),a constraint language which operates on variables of integer values.Like CLP solvers in general,CLP(FD)solvers are embedded either into standalone platforms such as the ILOG OPL Studio[2]or host languages,such as C[3],Java[4],Oz[5]or Prolog[6,7].In CLP(FD),FD stands forﬁnite domain,because each variable has aﬁnite set of integer values which it can take.These variables are connected by the constraints,which propagate the change of the domain of one variable to the domains of others.A constraint can be thought of like a“daemon”which wakes up when the domain of one(or more)of its variables has changed, propagates the change and then falls asleep again.This change can be induced either by an other constraint or by the distribution or labeling process,which enumerates the solutions by successively substituting every possible value into the variables.Constraints can be divided into two groups: simple and global constraints.The former always operate on aﬁxed number of arguments(like X=Y),while the latter are more generic and can work with a variable number of arguments (e.g.,“X1,X2,...,X n are all diﬀerent”).Many solvers allow the users to implement user-deﬁned constraints.However,the speciﬁcation languages vary.In some cases,a speciﬁc syntax is deﬁned for this purpose,in others,the host lan-guage is used.There are several problems with this.First,CLP(FD)programmers using diﬀerent systems could have serious diﬃculties sharing such constraints because of the lack of a common description language.Second,to deﬁne constraints,one usually has to know the solver in greater detail than if merely using the predeﬁned ones.Inspired by these problems,Nicolas Beldiceanu suggested a new method for deﬁning and describing globalﬁnite domain constraints[8].After The results reported in this paper were presented at the CS2conference held at Szeged,July1–4.2002.studying his theory,I decided to put it into practice by implementing a parser of Beldiceanu’s ab-stract description language(ADL),as an extension to the CLP(FD)library of SICStus Prolog[9, Sect.CLPFD],a full implementation of the CLP(FD)language.The paper is structured as follows.Section2introduces the theory of Beldiceanu,explains how constraints may be represented by graphs and describes the ADL in some detail.Section3 speciﬁes the concrete syntax of the language used by the implementation,Sect.4presents the implemented programs capable of understanding such a description.Section5gives some ideas about the possible directions of future research and development,andﬁnally Sect.6concludes the paper.2The TheoryIn[8],Beldiceanu speciﬁes a description language which enables mathematicians,computer sci-entists and programmers of diﬀerent CLP systems to share information on global constraints in a way that all of them understand.It also helps to classify global constraints,and as a most important feature,it enables us to write programs which,given only this abstract description, can automatically generate parsers,type checkers and propagators(pruners)for speciﬁc global constraints.Beldiceanu has also deﬁned a large number of constraints in the ADL.Most of them are already known,but the slight modiﬁcation of existing descriptions has resulted in several new constraints. The potential of these modiﬁcations arose only with the use of this schema.Section2.1introduces the essential concepts of Beldiceanu’s theory,Sect.2.2presents the most important features of the ADL,ﬁnally Sect.2.3illustrates the usage through the simple example of the widely used element constraint.2.1Representing Constraints as GraphsIn order to create an inter-paradigm platform,Beldiceanu reached for a device that is abstract enough and capable of depicting relations between members of a set:the directed graph.Before we can show how graphs can represent global constraints,three concepts have to be introduced:1.The initial graph is a regularly structured graph,which is characteristic of the constraint andthe number of arguments1,but is independent from the speciﬁc values of the arguments.2.The elementary constraint is a very simple constraint with few arguments,such as X=Y.3.The graph properties are restrictions on the number of arcs,sources,connected components,etc.The description of a constraint speciﬁes how the initial graph should be built.Its vertices are assigned one or more variables from the constraint,while the arcs connecting the vertices are generated according to a regular pattern.Finally the chosen elementary constraint is assigned to each arc.The variable belonging to the start point of the arc will become theﬁrst argument of the elementary constraint,while the variable assigned to the endpoint will become the second argument.Note that in general,the elementary constraint need not be binary,if it has more arguments,then a hypergraph is built using arcs with the required number of endpoints.Every distinct instantiation of the constraint arguments results in a separate instance of the constraint.For every such instance,a diﬀerentﬁnal graph is derived from the common initial graph by keeping those arcs for which the elementary constraint holds.If a vertex is left without connecting arcs,the vertex itself is also removed.The global constraint succeeds if and only if the speciﬁed graph properties hold for thisﬁnal graph.The graph of a simpliﬁed variant of the element constraint can be seen in Fig.1.This constraint serves as an example throughout this paper,and it is explained in detail in Sect.2.3.For now, it is enough to know that it succeeds if itsﬁrst argument,a single variable(denoted by A in the ﬁgure),is equal to a member of its second argument,a list of values(denoted by B,C,D and E). The required graph property is that the number of arcs should be exactly one.1As already mentioned,global constraints may(and usually do)have variable number of arguments.A i Bi C i D i E i T =E =c ='=(a)Initial graph 3i 1i 3i i 4i T =E =c ='=(b)An instance of (a)3i 3i E =(c)Final graphFig.1.The graph of the simpliﬁed element constraint2.2The Abstract Description Language (ADL)The most important feature of the ADL is the ability to describe how the initial graph has to be generated,what is the elementary constraint to be assigned to the arcs,and what graph properties must hold for the ﬁnal graph.Beside these,the ADL gives means to limit the set of values to be accepted in the constraint arguments,too.We have to specify the type of each argument,and we may also pose further restric-tions on the values.Any concrete application of the constraint that violates these preconditions will be considered as erroneous.The syntactic order of these language elements in a concrete deﬁnition reﬂects the order in which they are interpreted:the type and value restrictions are followed by the graph generation parameters,ﬁnally the required graph properties are speciﬁed.The following paragraphs discuss the language features in the very same order.Argument type restrictions.According to the schema of Beldiceanu,all arguments of the global constraint must be typed.There are three simple data types and a compound type,which are widely used.These are:int is a constant integer;atom is a character sequence (just like a Prolog atom);dvar is a domain variable (which could also be a constant as an special case);collection(Attr 1-Type 1,Attr 2-Type 2,...)is an ordered list of items ,each item being aset of labeled attributes,where Attr i and Type i are the label and type of the i th attribute,respectively.This type speciﬁcation does not require the items of such a collection to have all the attributes speciﬁed and also allows them to have additional attributes.It only requires the values of the given attributes to have the right type.An example collection and its type speciﬁcation (taken from [8])is shown in Fig.2.The type RECTANGLES corresponds to a collection of rectangles,each rectangle being deﬁnedin both dimensions by its origin and either its size or its end.The following is the typedeﬁnition of RECTANGLES and a sample instance of it,that contains two rectangles,one givenwith its size,the other with its endpoint.(The attributes of each rectangle are separated byspaces,the two rectangles are separated by a comma.)RECTANGLES:collection(ori1-dvar,siz1-dvar,end1-dvar,ori2-dvar,siz2-dvar,end2-dvar)RECTANGLES ={ori1-5siz1-20ori2-5siz2-10,ori1-25end1-45ori2-15end2-25}E T 1st 2nd Fig.2.An example collectionThere are other compound data types,too,like list or term ,which are rarely used in the numerous existing constraint descriptions.Argument value restrictions.In addition to type restrictions it is also possible to specify preconditions on the values of the arguments.These conditions can be expressed with the following formulæ:Name Relop Expression means Name must be in relation Relop with Expression .Here Name is the name of either an argument or an attribute of a collection,in the form Coll .Attr ,Coll being the collection.Relop is a relational operator,like =or ≥.Expression is an arbitrary expression consisting of constants,other names and mathematical operators.Name in {List }means Name (same as before)must appear in List ,a list of comma separated constants.distinct(Coll /Attr )means that all appearances of attribute Attr in the collection Coll must be distinct,i.e.no two attributes of this name can share the same value.required(Coll .Attr )means that all items in collection Coll must have attribute Attr speciﬁed.There are several other value restricting statements,but those are seldom used.Graph generation parameters.The initial graph generation consists of three phases.In the ﬁrst phase the vertices are created,in the second phase they are connected by arcs,and in the third phase,the speciﬁed elementary constraint is assigned to each arc.In the most common case,one has to specify an input collection to create the vertices:each element of this collection is assigned to a vertex.The collection may either be a constraint argument or it can be built for this purpose.The created vertices provide the input of the arc generator,which manages the second phase.Each generator incorporates a regular pattern,which is reﬂected in the created set of arcs.The arity of the arcs is characteristic of the generator,and it must also match the arity of the speciﬁed elementary constraint.In general,the arc generator may require the vertices to be divided into disjoint subsets.In that case,not one but several input collections must be speciﬁed,each of these is mapped to a separate subset of vertices.Currently,most existing arc generators need a single set of vertices (i.e.,one collection)as an input,and there are two of them expecting two.Figure 3shows four example arc generators.All of these generators create binary arcs,which means that they can be used with binary elementary constraints only.(This is the most common case.)The loop generator connects each vertex to itself.The path generator exploits that the collections are ordered lists,and connects the ﬁrst vertex to the second,the second to the third,and so on.The clique generator connects all vertices to all others by default,but it can have a relational operator as an argument,in which case it only connects vertices with indices which sustain the relation.Such a case is shown in the ﬁgure.The product generator gets two sets as an input,and connects all the vertices in the ﬁrst set to all the vertices in the second set.This generator can also have a relational operator as an argument.loop i c 1i c 2i c 3path i i i 123E E clique(<)i i i i 12E E c c d d ©producti i i i 12a b E E d d Fig.3.Arc generatorsThe elementary constraint,the third ingredient of the graph generation,is basically a mathem-atical relation containing symbolic references to values assigned to the vertices (i.e.,the endpoints of the arcs).A constraint deﬁnition contains three terms to specify this information.We have to determine the input collection(s),select the arc generator by its name,and deﬁne the elementary constraint assigned to the arcs.Graph property requirements.These statements also have the form of an equation,with a graph property name on the left hand side,constants and arguments of the global constraint on the right.Let us see several graph properties:nvertex is the number of vertices;2narc is the number of arcs;ncc is the number of connected components;nscc is the number of strongly connected components;nsource is the number of sources(those vertices which do not have arcs leading into them); nsink is the number of sinks.2.3An Example–The element ConstraintThe element constraint is one of the most common global constraints.It receives a single item and a set of items as arguments and it succeeds iﬀthe item is a member of the set.In some implementations,both the item and the elements of the set may be domain variables,but in the following interpretation the elements of the set must be constants.The formal deﬁnition of element according to[8]is shown in Fig.4,an instance of its graph with speciﬁc arguments was presented in Fig.1.It can be explained as follows.1.The element constraint has two arguments(line1).2.Theﬁrst,called ITEM is a collection with two attributes,index and value,both are domainvariables(line2).The second argument,called TABLE is also a collection with two attributes, also called index and value,but these are constants(line3).3.The following restrictions must hold:–both attributes of both collections must be speciﬁed in all items(lines4–5);–there must be exactly one item in ITEM(line6);–the indices in both collections must be between1and the size of TABLE(lines7–8);–all indices in TABLE must be distinct(line9).4.The arc generator is product(line11),which requires two collections as its input,namelyITEM and TABLE(line10).5.The elementary constraint assigned to the arcs appears in lines12–13.It is to be read like this:the value assigned to theﬁrst endpoint of the arc([1])is a member of the ITEM collection,and its attributes labeled as index and value must both be equal to the equivalent attributes of the value assigned to the second endpoint([2]),which is a member of the TABLE collection.The syntax looks a bit weird and perhaps even confusing,this question is addressed in Sect.3.1.6.The number of arcs must be exactly1in theﬁnal graph(line14).Note.It might seem strange to deﬁne ITEM as a collection when it must have exactly one element (line6).However,passing the index and value as two separate arguments of the constraint would be less symmetric with respect to TABLE.Another advantage is that ITEM,being a collection,can serve directly as an input for the product arc generator.2This property is sensible to examine,because unconnected vertices are removed from the graph,therefore it is not necessarily equal to the size of the input collection.1Constraint:element(ITEM,TABLE)2Arguments:ITEM:collection(index-dvar,value-dvar)3TABLE:collection(index-int,value-int)4Restrictions:required([ITEM.index,ITEM.value]),5required([TABLE.index,TABLE.value]),6|ITEM|=1,7ITEM.index≥1,ITEM.index≤|TABLE|,8TABLE.index≥1,TABLE.index≤|TABLE|,9distinct(TABLE/index)10Arc input:ITEM,TABLE11Arc generator:product12Arc constraint:ITEM.index[1]=TABLE.index[2]∧13ITEM.value[1]=TABLE.value[2]14Graph property:narc=1Fig.4.The element constraint in abstract syntax3The Concrete SyntaxIn order to be able to put the theory into practice,we had to deﬁne a concrete syntax of the language.The chosen representation closely resembles the abstract syntax,but follows the syntax of Prolog,too.This has the advantage that it can be eﬀortlessly parsed by a Prolog program.This work has helped to discover weaknesses of the ADL.First,it turned out that the semantics of the distinct operator is unclear in certain contexts,because it is under-speciﬁed.Second,as it was already noted at the end of the previous section,the syntax of the elementary constraint speciﬁcation can be confusing.Section3.1covers the two problematic issues and suggests a solution to both.Section3.2 illustrates the concrete syntax itself,supported by the updated version of the already familiar element example.3.1Clarifying the Language SpeciﬁcationThe problem of the distinct operator.Let us consider the following type declaration of a collection of collections:COLL:collection(c-collection(val-int))Such a data structure can be used to model diﬀerent data in diﬀerent constraints.Two of these are the following:1.A list of sets,where each set must have distinct elements in itself,but the same element canappear in more than one set.2.A partitioning of a single set,in this case all elements must be distinct,no element can appeartwice in the whole construct.Since their type signature is the same,they must be distinguished with value restrictions.Unfor-tunately,weﬁnd that we cannot express both with distinct statements.Moreover,it is unclear which of these distinct(COLL/c/val)really means.The inability to exactly specify what values are to be selected leads us to the deﬁnition of two concepts in the following paragraph.Selectors and designators.When we refer to attributes of items of collections,sometimes we want to reach single values,in other cases we need the list of values of all items within the collection.The required and distinct operators are good examples of the two possibilities,respectively.Keeping the notation of [8],which uses the name designator to refer to a sequence of names selected by slashes,let us introduce two new concepts,deﬁned with BNF notation as follows:selector ::=Coll |selector .Attrdesignator ::=selector |designator /AttrSelectors can be used to point out single values.They state something about values of items of a collection separately .Designators,on the other hand,point to a list of values.They state something about the values in all the items of a collection together .By starting a designator with a selector,we express that we want to divide the list of all the values into sublists and state something about these sublists separately.The division points are determined by the selector part of the designator.To clarify this,Fig.5shows a somewhat degenerated collection as a tree,along with two designators and the corresponding sublists marked with ovals.C:collection(a-collection(b-collection(c-int)))q q q q q q q q ¢¢¢f f f ¢¢¢f f f d d d ¢¢¢f f f q q q q q q t t t d d d q q q &&&& q C a b c £¢ ¡£¢ ¡£¢ ¡d §¦¤¥§¦¤¥§¦¤¥C.a.b/c §¦¤¥C.a/b/cFig.5.The meaning of designatorsIn certain contexts only selectors are accepted.Among others,such places are where the dot notation was already used,such as the argument of required ,or TABLE.index ≥1in Fig.4.In the latter we want to express that all values labeled as index must be greater than or equal to 1,separately.Elsewhere designators are required.The argument of distinct is such a place.One would also use a designator to count those items of a collection which possess a certain attribute.Then one needs to write |COLL/attr|,because COLL/attr brings all the items with attr attribute together into a list,and |...|returns the length of this.Now let us return to the problem of distinct .In the example presented there,the statement distinct(COLL.c/val)means that for all c collections separately,the val values must be distinct,but the same value can appear in more than one collection (case 1).distinct(COLL/c/val),on the other hand,means that the list of all values in all collections must be distinct (case 2).The elementary constraint notation.As we have seen in Fig.4,ITEM.value[1]means the value of the value attribute of the ﬁrst argument which is the ITEM collection.Thus we can say that the general form is something like Coll .Attr [ArgIndex ].This is rather confusing and does not resemble any of the notations we are used to:–the speciﬁcation of ITEM is redundant,because it is well known from the graph structure that theﬁrst argument of the elementary constraint must be an item of that collection;–the position of the index1between the brackets is misleading because this notation suggests some kind of array indexing,which is not the case.We would be better oﬀwith a notation like Args[1].value(where Args would be an array of all arguments of the elementary constraint)or Arg1.value.As we will see,the concrete syntax usesa very similar notation.3.2The Prolog-like Concrete SyntaxAs stated in the introduction of Sect.3,the chosen representation,while closely resembling the abstract syntax,follows the syntax of Prolog.Hence,each global constraint is described by a Prolog clause with seven arguments,as shown in Fig.6for the element constraint.These arguments are the following:1.the name and arguments of the global constraint(as a Prolog term);2.the list of type restrictions of the form Arg-Type where Arg is the name of the argument andType is the type speciﬁcation;3.the list of value restrictions in a form very similar to the abstract syntax,with the exceptionof|COLL|which should be written as size(COLL),and all the relational operators must be written in Prolog notation;4.the arc generator input(a list of collections);5.the name of the arc generator;6.the elementary constraint in the form Args=>Body,where Args is a collection of the argu-ments of the elementary constraint and Body is the constraint itself(#=and#/\are operators of the host language,basically they mean=and∧,respectively);7.the list of graph properties.Inline collections have a somewhat diﬀerent syntax than the one in Fig.2.They can be written as follows(note the diﬀerence in the use of commas and semicolons):–a collection has the form{Item1;Item2;...};–each Item i above has the form Att1-Val1,Att2-Val2,...where Att i is an attribute name and Val i is a value.The lines of Fig.6correspond respectively to the lines of Fig.4,and the deﬁnition as a whole should be self-explanatory.However,two things are worth mentioning.One is that we have chosen to represent the arguments of the elementary constraint as items of a collection.In the body,we need to refer to these items and their attributes.However,there no syntax is deﬁned to access the attribute of a single item of a collection,therefore we call for a trick.{A}means a collection with a single item(A),therefore{A}.index will expand to the index of this single element.The other point to note that the relational operator#=comes from the SICStus CLP(FD) library,therefore,after expanding the selectors,the statement will become a valid CLP(FD)ex-pression.The advantages of this will be discussed in Sect.4.2.4The ImplementationThe schema created by Beldiceanu allows us to test whether the relation expressed by a global constraint holds for a given set of concrete arguments.However,it does not deal with the more important case where only the domains of the arguments are speciﬁed,but their speciﬁc values are unknown.In such a case we need an algorithm to prune the domains of the arguments by deleting those values that would certainly result in aﬁnal graph not satisfying the properties. This question is fundamental in practical applications,therefore it is addressed by this section.1graphfd:global(element(Item,Table),2[Item-collection(index-dvar,value-dvar),3Table-collection(index-int,value-int)],4[required(Item.index),required(Item.value),5required(Table.index),required(Table.value),6size(Item)=:=1,7Item.index>=1,Item.index=<size(Table),8Table.index>=1,Table.index=<size(Table),9distinct(Table/index)],10[Item,Table],11product,12{A;B}=>{A}.index#={B}.index#/\13{A}.value#={B}.value,14narc=1).Fig.6.The element constraint in concrete syntaxDevelopment was launched with two goals in mind.Theﬁrst task was to implement a relation checker,a realization of the testing feature oﬀered by the schema,and a dumb propagator built on this checker.By and large,this task isﬁnished,the results are presented by Sect.4.1.The second task was to implement an direct propagator capable of pruning variable domains based on an analysis of the current state of the graph,with the required properties in view.This task is much bigger,the development is still in an early stage.Its current state and features are introduced by Sect.4.2.Both tasks are implemented in SICStus Prolog[9],extending its CLP(FD)library by utilizing the interface for deﬁning global constraints.This allows thorough testing of both the program and the theory itself in a trusted environment.4.1The Complex Relation Checker and the Generate-and-Test PropagatorTheﬁrst stage was to implement the complex relation checker,a program that checks whether the relation deﬁned by the global constraint holds for a given set of values,but does no pruning at all.It includes the following features:–complete type checking(dvar is interpreted as int);–full support of selectors and designators introduced in Sect.3.1;–support for value restriction with the most frequent statements:•distinct and required;plus•arbitrary Prolog calls which must succeed for the restriction to hold;•size(...)is replaced by the length of a collection or list.–full set of built-in arc generators;–extensive set of supported graph properties.When called,the relation checker is given a constraint with fully speciﬁed arguments,and reports the result of the type check,the restriction check,and whether the graph properties hold for the ﬁnal graph.The output of two example runs can be seen in Fig.7.In theﬁrst case,theﬁrst argument appears in the collection passed in the second argument,while in the second case it does not.。