外文翻译《数据库系统》
Database systemA database may be defined as a collection of interrelated data stored together with as little redundancy as possible to serve one or more applications in an optimal fashion; the data are stored so that they are independents of programs which use the data; a common and controlled approach is used in adding new data and in modifying and retrieving existing data within the data base one system is said to contain a collection of databases if they are entirely separate in structure.The restructuring should be possible without having to rewrite the application program and in general should cause as little upheaval as possible the ease with which a database can be changed will have a major effect on the rate at whichdata-processing application can be developed in a corporation.The term data independence is often quoted as being one of the main attributes of a database int implies that the data and the may be changed without changing the other, when a single setoff data items serves a variety of applications, different application programs perceive different relationships between the data items,to a large extent database organization is concerned with the as how and where the data are stored.A database used for many applications can have multiple interconnection referred to as entities.An entity may be a tangible object or no tangible if it has various properties which we may wish to record.It can describe the real world.The data item represents an attribute and the attribute must be associated which the relevant entity.We relevant entity we design values to the attributes one attribute has a special significance in that it identifies the entity.Logical data description is called a model.We must distinguish a record and a record examples, when talking about all personnel records when it is really a record type, not combined with its data value.A model is used to describe the database used storage in the database data item type and record types of general charts, subschema paragraph refers to an application programmer view of data, many different patterns can get from one mode. T he schema and the subschema are both used by the database management system the primary function of which is to serve the application programs by execution their data operations.A DBMS will usually be handling multiple data calls concurrently, it must organize its system buffers so that different data operations can be in process together, it provides a data definition language to specify the conceptual schema and most likely some of the details regarding the implementation of the conceptual schema by the physical schema the describe the conceptual schema in terms for a “data model”.The choice of a data model is a difficult one, since it must be such enough in structure to describe significant aspects of the real world, yet it must be possible to determine fairly automatically an efficient implementation of the conceptual conceptual schema by a physical schema.It should be emphasized that while a DBMS might be used to build small databases many databases involve millions of bytes and an inefficient implementation can be disastrous.Logical schemas are defined as data, pedals with the underlying structure of particular database management systems superimposed on them at the present time there are three main underlying structures for database management systems these are:relational,hierarchical,network.The hierarchical and network structures have been used for DBMS since the 1960’s . the relational structure was introduced in the early 1970’s.In the relational model two-dimensional tables represent the entities and their relationships every table represents an entities are represented by common columns containing values from a domain or range of possible values .The end user is presented with a simple data model his and her request and don not reflect any complexities due to system-oriented aspects a relational data model is what the user sees , but it is mot necessarily what will be implemented physically.The relational data model removes the details of storage structure and access strategy from the user inter-face the model providers a relatively higher degree of data to make use of this property of the relational data model however, the design of the relations must be complete and accurate.Although some DBMS based on the relational data model are commercially available today it is difficult to provide a complete set of operational capabilities with required efficiency on a large scale it appears today that technological improvements in providing faster and more reliable hardware may answer the question positively.The hierarchical data model is based no a tree-like structure made up of nodes and branches a node is a collection of data attributes describing the entity at that opine the highest node of the hierarchical.A hierarchical data model always starts with a root node every node consists of one or more attributes describing the entity at that node dependent nodes can follow the succeeding levels the mode in the receding level becomes the parent node of the new dependent nodes a parent node can have one child node as a dependent or many children nodes the major advantage of the hierarchical data model is the existence of proven database management systems that use the hierarchical data model as the basic structure there is a reduction of data dependency but any child mode is accessible only in a clumsy way this often results in a redundancy in stored data.The network data model interconnects the entities of an enterprise into a network in the network data model a database.Consists of a number of areas an area contains records in turn a recode may consist of fields a set which is a grouping of records may reside in an area or span a number of areas a set type is based on the owner record type and the member record type the many-to-many relation-ship which occurs quite frequently in rap fife can be implemented easily the network data model is very compel the application programmer must be familiar with the logical structure of the database.To meet the multiple users in a particular sector of the need for a variety of applications, according to some data model in the computer system in the organization, storage and use of data collection linked to each other.数据库系统一个数据库可以被定义成一个相关数据的集合，这个集合尽可能小的冗余为一个或多个应用程序在最理想的方式下服务，存贮数据的目的是使他们与使用数据的程序独立，一种相同的控制方法用于数据库更新数据和修改，恢复已存在的数据，如果一个系统在结构上完全分离，则他们被称为一个数据库集合。
管理信息系统外文翻译 (2)
毕业设计（论文）外文文献翻译毕业设计（论文）题目翻译（1）题目管理信息系统翻译（2）题目数据库管理系统的介绍学院计算机学院专业姓名班级学号Management Information SystemIt is the MIS(Management Information System ) that we constantly say that the management information system , and is living to emphasize the administration , and emphasizes that it changes into more and more significantly and more and more is universalized in the contemporary community of message . MIS is a fresh branch of learning, and it leaped over several territories, and for instance administers scientific knowledge, system science, operational research, statistic along with calculating machine scientific knowledge. Is living on these the branches of learning base, and takes shape that the message is gathered and the process means, thereby take shape the system that the crossbar mingles.1. The Management Information System Summary20 centuries, in the wake of the flourishing development of whole world economy, numerous economists propose the fresh administration theory one by one. Xi Men propose the administration and was dependent on idea to message and decision of strategic importance in the 50’s 20 centuries. The dimension of simultaneous stage is admitted issuing cybernetics, and he thinks that the administration is a control procedure. In 1958, Ger. write the lid: “ the administration shall obtain without delay with the lower cost and exact message, completes the better control “. This particular period, the calculating machine starts being used accountancy work. The data handling term has risen.In 1970, Walter T.Kennevan give administration that has raised the only a short while ago information system term to get off a definition: “ either the cover of the book shape with the discount, is living appropriately time to director, staff member along with the outside world personnel staff supplies the past and now and message that internal forecasting the approaching relevant business reaches such environment, in order to assist they make a strategic de cision”. Is living in this definition to emphasize, yet does not emphasize using the pattern, and mention the calculating machine application in the way of the message support decision of strategic importance.In 1985, admonishing information system originator, title Buddhist nun Su Da university administration professor Gordon B.Davis give the management information system relatively integrated definition, in immediate future “ administer the information system is one use calculating machine software and hardware resources along with data bank man - the engine system.It be able to supply message support business either organization operation, administration or the decision making function. Comprehensive directions of this definition management information system target and meritorious service capacity and component, but also make known the management information system to be living the level that attains at that time.1.1 The Developing History of MISThe management information system is living the most primarily phase iscounting the system, the substance which researched is the regular pattern on face between the incremental data, it what may separate into the data being mutually related and more not being mutually related series, afterwards act as the data conversion to message.The second stage is the data are replaced the system, and it is that the SABRE that the American airline company put up to in the 50’s 20 centuries subscribes to book the bank note system that such type stands for. It possess 1008 bank note booking spots, and may access 600000 traveler keep the minutes and 27000 flight segments record. Its operation is comparatively more complex, and is living whatever one “spot ”wholly to check whether to be the free place up some one flight n umbers. Yet through approximately attending school up to say, it is only a data and replaces the system, for instance it can not let know you with the bank note the selling velocity now when the bank note shall be sell through, thereby takes remedying the step. As a result it also is administer information system rudimentary phase.The third phase is the status reports system, and it may separate into manufacture state speech and service state and make known and research the systems such as status reports and so on. Its type stands for the production control system that is the IBM corporation to the for instance manufacture state speech system. As is known to all, the calculating machine corporation that the IBM corporation is the largest on the world, in 1964 it given birth to middle-sized calculating machine IBM360 and causes the calculating machine level lift a step, yet form that the manufacture administration work. Yet enormously complicatedly dissolve moreover, the calculating machine overtakes 15000 difference components once more, in addition the plant of IBM extends all over the American various places to every one components once more like works an element, and the order of difference possess difference components and the difference element, and have to point out that what element what plant what installation gives birth to, hence not merely giving birth to complexly, fitting, installation and transportation wholly fully complex. Have to there be a manufacture status reports system that takes the calculating machine in order to guarantee being underway successfully of manufacture along with else segment as the base. Hence the same ages IBM establish the systematic AAS of well-developed administration it be able to carry on 450 professional work operations. In 1968, the corporation establishes the communal once more and manufactures informationsystem CMIS and runs and succeeds very much, the past needs 15 weeks work, that system merely may be completed in the way of 3 weeks.It is the data handling system that the status reports system still possess one kind of shape , and that it is used for handles the everyday professional work to make known with manufacture , and stress rests with by the handwork task automation , and lifts the effectiveness with saves the labor power . The data handling system ordinarily can not supply decision of strategic importance message.Last phase is the support systems make a strategic decision, and it is the information system being used for supplementary making a strategic decision. That system may program and the analysis scheme, and goes over key and the error solve a problem. Its proper better person-machine dialogue means, may with not particularlythe personnel staff who have an intimate knowledge of the calculating machine hold conversation. It ordinarily consists of some pattern so as to come into being decision of strategic importance message, yet emphasize comprehensive administration meritorious service capacity.1.2 The Application of Management Information SystemThe management information system is used to the most base work, like dump report form, calculation pay and occurrences in human tubes and so on, and then developing up business financial affairs administrations and inventory control and so on individual event operational control , this pertains to the electron data handling ( EDP Data Processing ) system . When establish the business data bank, thereby possess the calculating machine electric network to attain data sharing queen , the slave system concept is start off , when the implementation the situation as a whole is made program and the design information system ,attained the administration information system phase . In the wake of calculating machine technique progress and the demand adjust the system of people lift further, people emphasize more furthermore administer the information system phase. Progress and people in the wake of the calculating machine technique lift at the demand adjust the system further, people emphasize more furthermore to administer the information system whether back business higher level to lead makes a strategic decision this meritorious service capacity, still more lay special emphasis on the gathering to the external message of business and integrated data storehouse, model library , means storehouse and else artificial intelligence means whether directly to decision of strategic importance person , this is the support system ( DDS ) mission making a strategic decision.There is the part application that few business start MIS inner place the limit of the world at the early days of being living in the 70’s 20 centuries. Up at the moment, MIS is living, and there be the appropriatePopularization rate in every state nation in world, and nearly covered that every profession reaches every department.1.3 The Direction of MIS DevelopmentClose 20 curtains; external grand duke takes charge of having arisen3 kinds of alternations:A. Paying special attention to the administration being emphasized toestablishing MIS’s s ystem, and causing the administration technique headfor the ageing.B. The message is the decision of strategic importance foundation, and MISsupplies the message service in the interest of director at all times.C. Director causes such management program getting in touch with togetherwith the concrete professional work maneuver by means of MIS. not merelybig-and-middle-sized business universally establish MIS some small-sizebusiness also not exceptions of self, universally establish the communaldata network, like the electronic mail and electron data exchange and so on,MIS supplied the well support environment to the application of Intranet’stechnique to speedily developing of INTERNET especially in the past fewyears in the interest of the business.Through international technique development tendency is see, in the 90’s 20 centuries had arisen some kinds of brand-new administration technique.1. Business Processes Rebuild (BPR)A business should value correctly time and produce quality, manufacturing cost and technical service and so on several section administrations, grip at the moment organization and the process compose once more,andcompletes that meritorious service capacity integrationist, operation processization and organization form fluctuation. Shall act as the service veer of middle layer management personnel staff the decision of strategic importance of the director service?2. Intelligentization Decision Support System (IDSS)The intelligentization decision of strategic importance support system was sufficiently consider demand and the work distinguishing feature of business higher level personnel staff.3. Lean Production (LP)Application give birth to on time, comprehensive quality control and parallel project that picked amount is given birth to and so on the technique, the utmost product design cutting down and production cycle, raise produce quality and cuts down the reproduced goods to reserve, and is living in the manufacture promote corps essence, in order to meet the demand that client continuously changes.4. Agile Manufacture (AM)One kind of business administration pattern that possess the vision, such distinguishing feature is workers and staff members’ quality is high, and the organization simplifies and the multi-purpose group effectiveness GAO message loading is agile and answers client requires swiftly.2. The Effect To The Business Administration of MIS DevelopmentThe effect to the business administration of the management information system development is administered the change to business and business administration of information system development and come into being and is coming into being the far-reaching effect with.Decision of strategic importance, particularly strategic decision-making may be assisted by the administration information system, and its good or bad directly affects living and the development up the business. The MIS is impeding the orientation development that the administration means one another unites through quality and ration. This express to utilize the administration in the calculation with the different mathematical model the problem in the quantitative analysis business.The past administer that the problem is difficult to test, but MIS may unite the administration necessaries, and supply the sufficient data, and simulates to produce the term in the interest of the administration.In the wake of the development of MIS, much business sit up the decentralizedmessage concentration to establish the information system ministry of directly under director, and the chief of information system ministry is ordinarily in the interest of assistant manager’s grade. After the authority of business is centralized up high-quality administration personnel staff’s hand, as if causing much sections office work decrease, hence someone prophesy, middle layer management shall vanish. In reality, the reappearance phase employed layer management among the information system queen not merely not to decrease, on the contrary there being the increase a bit.This is for, although the middle layer management personnel staff getting off exonerate out through loaded down with trivial details daily routine, yet needs them to analyses researching work in the way of even more energy, lift further admonishing the decision of strategic importance level. In the wake of the development of MIS, the business continuously adds to the demand of high technique a talented person, but the scarce thing of capability shall be washed out gradually. This compels people by means of study and cultivating, and continuously lifts individual’s quality. In The wake of the news dispatch and electric network and file transmission system development, business staff member is on duty in many being living incomparably either the home. Having caused that corporation save the expenses enormously, the work efficiency obviously moves upward American Rank Zeros corporation the office system on the net, in the interest of the creativity of raise office personnel staff was produced the advantageous term.At the moment many countries are fermenting one kind of more well-developed manufacturing industry strategy, and become quickly manufacturing the business. It completely on the basis of the user requirement organization design together with manufacture, may carry on the large-scale cooperation in the interest of identical produce by means of the business that the flow was shifted the distinct districts, and by means of the once more programming to the machinery with to the resources and the reorganization of personnel staff , constituted a fresh affrication system, and causes that manufacturing cost together with lot nearly have nothing to do with. Quickly manufacturing the business establishes a whole completely new strategy dependence relation against consumer, and is able to arouse the structure of production once more revolution.The management information system is towards the self-adoption and Self-learning orientation development, the decision procedure of imitation man who is be able to be better. Some entrepreneurs of the west vainly hope that consummate MIS is encircles the magic drug to govern the business all kinds of diseases; Yet also someone says, and what it is too many is dependent on the defeat that MIS be able to cause on the administration. It is adaptable each other to comprehend the effect to the business of MIS, and is favor of us to be living in development and the research work, and causes the business organization and administer the better development against MIS of system and administration means , and establish more valid MIS.The Source Of Article： Russ Basiura, Mike Batongbacal管理信息系统管理信息系统就是我们常说的MIS(Management Information System), 在强调管理，强调信息的现代社会中它变得越来越重要、越来越普及。
数据库系统原理英文PPT课件
I/O system : drivers
memory controllers (i.e. disk controller),
on the basis of secondary storage’s physical structures, such as storage structures, access method
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§1.2 Purpose of Database Systems (cont.)
• Data management on the basis of file systems
• Example
— customer_record=<c_name, c_id, street, city> in Customer_File
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§1.0 DB, DBMS, DBS
• Definitions in the textbook • Database (DB) — a collection of interrelated data, stored in systems as files • Database management system (DBMS) — DB, or a collection of interrelated data — set of programs to access the data in DB
• Databases and DBS touch all aspects of our lives • Banking: all transactions • Airlines: reservations, schedules • Universities: registration, grades • Sales: customers, products, purchases • Manufacturing: production, inventory, orders, supply chain • Human resources: employee records, salaries, tax deductions
外文科技文献译文-- 信息系统的开发和数据库开发
本科生毕业设计（论文）外文科技文献译文译文题目信息系统的开发和数据库开发(外文题目)Information System Development and Database Development系名称电子与信息工程系专业电子信息工程（通信工程）学号1115028学生姓名薛祥宇日期2015.4.16指导教师签名日期2015.4.16译文：信息系统的开发和数据库开发在许多组织中，从企业数据建模之初数据库开发，数据建模企业确定数据库和一般内容的范围。
这一步通常发生在一个组织的信息系统规划的过程中，它的目的是帮助企业建立一个全面的数据说明或解释，而不是特定数据库的设计。
为一个或多个信息系统的一个特定的数据库提供该组织保持数据的范围中记载的数据与公司数据模型（其可以涉及多个数据库）。
在企业数据建模，你检讨现行制度，需要支持的业务领域的性质，需要对抽象数据进一步说明，并规划一个或多个数据库开发项目的分析。
图1显示了松谷家具公司的企业数据的一部分的模型。
1.1信息系统体系结构如图1，高级数据模型也只是一般的信息系统架构（ISA），或一个组织的信息系统蓝图的一部分。
在信息系统的规划，你可以建立一个企业数据模型作为整个信息系统架构的一部分。
根据Zachman的（1987），索瓦和Zachman的（1992）的观点的信息系统架构由以下六个关键的组件组成：数据（图1示出，但也有其他方法）。
数据处理的操作（一个数据流图的都可以使用，与对象模型的方法，或者其它符号）。
网络，其组织和与商业伙伴之间的数据，其主传动机构（它可以通过网络拓扑映射连接并展示）。
人谁处理的数据和信息的实现，是在源和接收器（在用于数据的过程模型表明，发送者和接收者）。
实现事件和时间点（他们可以使用状态转换图等多种方式。
）的原因，事件和数据处理规则（通常在文本的形式显示出来，但也有许多图表的规划工具，如决策表）。
1.2信息工程信息系统的规划者按照特定的信息系统规划方法开发的信息系统架构。
外文文摘型数据库简介
外文文摘型数据库简介1．Ei Compendex工程索引数据库EI(The Engineering Index:工程索引)是工程技术领域的综合性检索工具，由美国工程信息中心编辑出版。
侧重提供应用科学和工程领域的文摘索引信息，涉及核技术、生物工程、交通运输、化学和工艺工程、照明和光学技术、农业工程和食品技术、计算机和数据处理、应用物理、电子和通信、控制工程、土木工程、机械工程、材料工程等学科。
Ei的数据来源于5100种工程类期刊、会议论文集和技术报告，每年大约增加文献25万篇。
2000年8月，Ei 推出Engineering Information Village-2（简称EI Village2 或EV2)新版本，对文摘录入格式进行了改进，首次将文后参考文献列入Compemdex 数据库。
用户在EI Village2网上可检索到1884年至今的文献。
EI Village2有“简易检索（Easy Search）”、“快速检索（Quick Search）”和“高级检索（Expert Search）”三种检索方法。
检索结果显示方式有：Citation（引文）、Abstracts（摘要）或Detailed record(详细记录)格式，可以通过文摘页左下角Full-Text Links链接Elsevier、Springer等全文数据库查阅全文。
EI Village2数据库及时报道全世界工程与技术文献，为科学研究者和工程技术人员提供专业化、实用化的最新文献信息服务。
2．SCI（科学引文索引）数据库科学引文索引（SCI）是国际学术界公认的“四大权威检索工具”之一，内容涵盖自然科学、工程技术、生物医学、社会科学、艺术与人文等170多个学科领域。
目前该数据库有“扩展版”和“核心版”2种版本。
2006年12月SCI Expanded扩展版收录期刊6613种、SCI核心版收录3766种期刊。
SCI数据每周更新。
SCI数据库检索系统有General Search(普通检索)、Cited Ref Saerch(引文检索)、Structure Search(结构检索)和Advanced Search(高级检索)四种检索方法。
数据库外文参考文献及翻译
数据库外文参考文献及翻译数据库外文参考文献及翻译SQL ALL-IN-ONE DESK REFERENCE FOR DUMMIESData Files and DatabasesI. Irreducible complexityAny software system that performs a useful function is going to be complex. The more valuable the function, the more complex its implementation will be. Regardless of how the data is stored, the complexity remains. The only question is where that complexity resides. Any non-trivial computer application has two major components: the program the data. Although an application’s level of complexity depends on the task to be performed, developers have some control over the location of that complexity. The complexity may reside primarily in the program part of the overall system, or it may reside in the data part.Operations on the data can be fast. Because the programinteracts directly with the data, with no DBMS in the middle, well-designed applications can run as fast as the hardware permits. What could be better? A data organization that minimizes storage requirements and at the same time maximizes speed of operation seems like the best of all possible worlds. But wait a minute . Flat file systems came into use in the 1940s. We have known about them for a long time, and yet today they have been almost entirely replaced by database s ystems. What’s up with that? Perhaps it is the not-so-beneficial consequences。
计算机专业外文翻译--信息系统开发和数据库开发
外文原文Information System Development and Database DevelopmentIn many organizations, database development from the beginning of enterprise data modeling, data modeling enterprises determine the scope of the database and the general content. This step usually occurs in an organization's information system planning process, it aims to help organizations create an overall data description or explanation, and not the design of a specific database. A specific database for one or more information systems provide data and the corporate data model (which may involve a number of databases) described by the organization maintaining the scope of the data. Data modeling in the enterprise, you review of the current system, the need to support analysis of the nature of the business areas, the need for further description of the abstract data, and planning one or more database development project. Figure 1 shows Pine Valley furniture company's enterprise data model of a part.1.1 Information System ArchitectureAs shown in figure 1, senior data model is only general information system architecture (ISA) or a part of an organization's information system blueprint. In the information system planning, you can build an enterprise data model as a whole information system architecture part. According to Zachman (1987), Sowa and Zachman (1992) views of an information system architecture consists of the following six key components:Data (Figure 1 shows, but there are other methods that).Manipulation of data processing (of a data flow diagram can be used, with the object model methods, or other symbols that).Networks, which organizations and in organizations with its main transmission of data between business partners (it can connect through the network topology map and to demonstrate).People who deal with the implementation of data and information and is the source and receiver (in the process model for the data shows that the sender and the receiver).Implementation of the events and time points (they can use state transition diagram and other means.)The reasons for the incident and data processing rules (often in the form of text display, but there are also a number of charts for the planning tools such as decision tables).1.2 Information EngineeringInformation systems planners in accordance with the specific information system planning methods developed information system architecture. Information engineering is a popular and formal methods. Information engineering is a data-oriented creation and maintenance of the information system. Information engineering is because the data-oriented, so when you begin to understand how the database is defined by the logo and when information engineering a concise explanation is very helpful. Information Engineering follow top-down planning approach, in which specific information systems from a wide range of information needs in the understanding derived from (for example, we need about customers, products, suppliers, sales and processing of the data center), rather than merging many detailed information requested ( orders such as a screen or in accordance with the importation of geographical sales summary report). Top-down planning will enable developers to plan more comprehensive information system, consider system components provide an integrated approach to enhance the information system and the relationship between the business objectives of the understanding, deepen their understanding of information systems throughout the organization in understanding the impact.Information Engineering includes four steps: planning, analysis, design and implementation. The planning stage of project information generated information system architecture, includingenterprise data model.1.3 Information System PlanningInformation systems planning objective is to enable IT organizations and the business strategy closely integrated, such integration for the information systems and technology to make the most of the investment interest is very important. As the table as a description, information engineering approach the planning stage include three steps, we in the follow-up of three sections they discussed.1. Critical factors determining the planningPlanning is the key factor that organizational objectives, critical success factors and problem areas. These factors determine the purpose of the establishment of planning and environment planning and information systems linked to strategic business planning. Table 2 shows the Pine Valley furniture company's key planning a number of possible factors, these factors contribute to the information systems manager for the new information systems and databases clubs top priority to deal with the demand. For example, given the imprecise sales forecasts this problem areas, information systems managers in the organization may be stored in the database additional historical sales data, new market research data and new product test data.2. The planning organizations set targetsOrganizations planning targets defined scope of business, and business scope will limit the subsequent analysis and information systems may change places. Five key planning targets as follows:●organizational units in the various sectors.●organizations location of the place of business operations.●functions of the business support organizations handling mission of the relevant group. Unlike business organizations function modules, in fact a function can be assigned to various organizations modules (for example, product development function is the production and sale of the common responsibility of the Ministry).●types of entities managed by the organization on the people, places and things of the major types of data.●Information System data set processing software applications and support procedures.3. To set up a business modelA comprehensive business model including the functions of each enterprise functional decomposition model, the enterprise data model and the various planning matrix. Functional decomposition is the function of the organization for a more detailed decomposition process, the functional decomposition is to simplify the analysis of the issue, distracted and identify components and the use of the classical approach. Pine Valley furniture company in order to function in the functional decomposition example in figure 2 below. In dealing with business functions and support functions of the full set, multiple databases, is essential to a specific database therefore likely only to support functions (as shown in Figure 2) provide a subset of support. In order to reduce data redundancy and to make data more meaningful, has a complete, high-level business view is very helpful.The use of specific enterprise data model to describe the symbol. Apart from the graphical description of this type of entity, a complete enterprise data model should also include a description of each entity type description of business operations and a summary of that business rules. Business rules determine the validity of the data.An enterprise data model includes not only the types of entities, including the link between thedata entities, as well as various other objects planning links. Showed that the linkage between planning targets a common form of matrix. Because of planning matrix need not be explicit modeling database can be clearly described business needs, planning matrix is an important function. Regular planning matrix derived from the operational rules, it will help social development activities that top priority will be sorting and development activities under the top-down view through an enterprise-wide approach for the development of these activities. There are many types of planning matrix is available, their commonalities are:●locations - features show business function in which the implementation of operational locations.●unit - functions which showed that business function or business unit responsible for implementation.●Information System - data entities to explain how each information system interact with each data entity (for example, whether or not each system in each entity have the data to create, retrieve, update and delete).●support functions - data in each functional entities in the data set for the acquisition, use, update and delete.●Information System - target indication for each information system to support business objectives.Figure 3 illustrate a possible functions - data entities matrix. Such a matrix can be used for a variety of purposes, including the following three objectives:1) identify gaps in the data entities to indicate the types of entities not use any function or functions which do not use any entity.2) found that the loss of each functional entities involved in the inspection staff through the matrix to identify any possible loss of the entity.3) The distinction between development activities if the priority to the top of a system development function for a high-priority (probably because it important organizational objectives related), then this area used by entities in the development of the database has a high priority. Hoffer, George and Valacich (2002) are the works of the matrix on how to use the planning and completion of the Information EngineeringThe planning system more complete description.2 database development processBased on information engineering information systems planning database is a source of development projects. These new database development projects is usually in order to meet the strategic needs of organizations, such as improving customer support, improve product and inventory management, or a more accurate sales forecast. However, many more database development project is the bottom-up approach emerging, such as information system user needs specific information to complete their work, thus beginning a project request, and as other information systems experts found that organizations need to improve data management and begin new projects. Bottom-up even in the circumstances, to set up an enterprise data model is also necessary to understand the existing database can provide the necessary data, otherwise, the new database, data entities and attributes can be added to the current data resources to the organization. Both the strategic needs or operational information needs of each database development projects normally concentrated in a database. Some projects only concentrated in the database definition, design and implementation of a database, as a follow-up to the basis of the development of information systems. However, in most cases, the database and associatedinformation processing function as a complete information systems development project was part of the development.2.1 System Development Life CycleGuide management information system development projects is the traditional process of system development life cycle (SDLC). System development life cycle is an organization of the database designers and programmers information system composed of the Panel of Experts detailed description, development, maintenance and replacement of the entire information system steps. This process is because Waterfall than for every step into the adjacent the next step, that is, the information system is a specification developed by a piece of land, every piece of the output is under an input. However shown in the figure, these steps are not purely linear, each of the steps overlap in time (and thus can manage parallel steps), but when the need to reconsider previous decisions, but also to roll back some steps ahead. (And therefore water can be put back in the waterfall!)Figure 4 on the system development life cycle and the purpose of each stage of the product can be delivered concise notes. The system development life cycle including each stage and database development-related activities, therefore, the question of database management systems throughout the entire development process. In Figure 5 we repeat of the system development life cycle stage of the seven, and outlines the common database at each stage of development activities. Please note that the systems development life cycle stages and database development steps一一对应exists between the relationship between the concept of modeling data in both systems development life cycle stages between.Enterprise ModelingDatabase development process from the enterprise modeling (system development life cycle stage of the project feasibility studies, and to choose a part), Organizations set the scope and general database content. Enterprise modeling in information systems planning and other activities, these activities determine which part of information systems need to change and strengthen the entire organization and outlines the scope of data. In this step, check the current database and information systems, development of the project as the main areas of the nature of the business, with a very general description of each term in the development of information systems when needed data. Each item only when it achieved the expected goals of organizations can be when the next step.Conceptual Data ModelingOne has already begun on the Information System project, the concept of data modeling phase of the information systems needs of all the data. It is divided into two stages. First, it began the project in the planning stage and the establishment of a plan similar to Figure 1. At the same time outlining the establishment of other documents to the existing database without considering the circumstances specific development projects in the scope of the required data. This category only includes high-level data (entities), and main contact. Then in the system development life-cycle analysis stage must have a management information system set the entire organization Details of the data model definition of all data attributes, listing all data types that all data inter-entity business linkages, defining description of the full data integrity rules. In the analysis phase, but also the concept of inspection data model (also called the concept behind the model) and the goal of information systems used to explain other aspects of the model of consistency categories, such as processing steps, rules and data processing time of timing. However, even if the concept is such detailed data model is only preliminary, because follow-up information system life cycle activities in the design of services, statements, display and inquiries may find that missing element ormistakes. Therefore, the concept of data often said that modeling is a top-down manner, its areas of operation from the general understanding of the driver, rather than the specific information processing activities by the driver.3. Logical Database DesignLogical database design from two perspectives database development. First, the concept of data model transform into relational database theory based on the criteria that means - between. Then, as the design of information systems, every computer procedures (including procedures for the input and output format), database support services, statements, and inquiries revealed that a detailed examination. In this so-called Bottom-up analysis, accurate verification of the need to maintain the database and the data in each affairs, statements and so on the needs of those in the nature of the data.For each separate statements, services, and so on the analysis must take into account a specific, limited but complete database view. When statements, services, and other analysis might be necessary to change the concept of data model. Especially in large-scale projects, the different analytical systems development staff and the team can work independently in different procedures or in a centralized, the details of their work until all the logic design stage may be displayed. In these circumstances, logic database design stage must be the original concept of data model and user view these independent or merged into a comprehensive design. In logic design information systems also identify additional information processing needs of these new demands at this time must be integrated into the logic of earlier identified in the database design.Logical database design is based on the final step for the formation of good data specifications and determine the rules, the combination, the data after consultation specifications or converted into basic atomic element. Most of today's database, these rules from the relational database theory and the process known as standardization. This step is the result of management of these data have not cited any database management system for a complete description of the database map. Logical database design completed, we began to identify in detail the logic of the computer program and maintenance, the report contents of the database for inquiries.4. Physical database design and definitionPhysical database design and definition phase decisions computer memory (usually disk) database in the organization, definition of According to the library management system for physical structure, the procedures outlined processing services, produce the desired management information and decision support statements. The objective of this stage is to design an effective and safe management of all data-processing database, the physical database design to closely integrate the information systems of other physical aspects of the design, including procedures, computer hardware, operating systems and data communications networks.5. Database ImplementationThe database prepared by the realization stage, testing and installation procedures for handling databases. Designers can use the standard programming language (such as COBOL, C or Visual Basic), the dedicated database processing languages (such as SQL), or the process of the non-exclusive language programming in order to produce a statement of the fixed format, the result will be displayed, and may also include charts. In achieving stage, but also the completion of all the database files, training users for information systems (database) user setup program. The final step is to use existing sources of information (documents legacy applications and databases and now needs new data) loading data. Loading data is often the first step in data from existing files and databases to an intermediate format (such as binary or text files) and then to turn intermediate loading data to a new database. Finally, running databases and related applicationsfor the actual user maintenance and retrieval of data. In operation, the regular backup database and the database when damaged or affected resume database.6. Database maintenanceDuring the database in the progressive development of database maintenance. In this step, in order to meet changing business conditions, in order to correct the erroneous database design, database applications or processing speed increase, delete or change the structure of the database. When a procedure or failure of the computer database affect or damage the database may also be reconstruction. This step usually is the longest in the database development process step, as it continued to databases and related applications throughout the life cycle, the development of each database can be seen as a brief database development process and data modeling concepts arise, logical and physical database design and database to achieve dealing with the changes.2.2 Information System developed by other meansSystem Development Life Cycle minor changes in law or its variant of the often used to guide information systems and database development. Information System is a life-cycle methodology, it is highly structured approach, which includes many checks and balances to ensure that every step of produce accurate results, and new or alternative information system and it must communications or data definitions consistent existing system needs consistency. System development life cycle because of the regular need to have a working system for a long time been criticized because only work in the system until the end of the whole process generated. More and more organizations now use rapid application development method, it is a includes analysis, design and implementation of steps to repeat the rapid iterative process until convergence to users the system so far. Rapid Application Development Act required the database has been in existence, and enhance system is mainly to the application of data retrieval application, but not to those who generate and modify database applications.The most widely used method of rapid application development is one of the prototype. The prototype system is a method of iterative development process, analysts and users through close co-operation, continuing to revise the system will eventually convert all the needs of a working system. Figure 6 shows prototype of the process. In this diagram we contains notes, briefly describes each stage of the prototype of the database development activities. Normally, when information systems problems were identified, tried only a rough concept of data modeling. In the development of the initial prototype, the design of the user wants to display and statements, and that any new database needs and define a term prototype database. This is usually a new database, copy the part of the existing system, but might also added some new content. When the need for new content, these elements are usually from external data sources, such as market research data, the general economic indicators or industry standards.When a prototype of a new version to repeat the achievement and maintenance of database activities. Usually only a minimum level of security and integrity control, because at this time the focus is as soon as possible to produce a prototype version can be used. But document management project also deferred to the final, only be used in the delivery of user training. Finally, once constructed an acceptable prototype, developers, and users will be the final decision of whether to prototype delivery and the use of the database. If the system (including database) efficiency is very low, then the system and database will be re-programming and re-organization in order to achieve the desired performance.Along with visual programming tools (such as Visual Basic, Java, Visual C + + and fourth generation language) increasingly popular use of visual programming tools can easily change the user interface with the system, the prototype is becoming the choice of system developmentmethodology. Customers using the prototype method statements and show changes to the content and layout is quite easy. In the process, the new database needs were identified, so it is the development of the use of the existing database should be amended. There is even the possibility of a need for a new database system prototype method, in such circumstances, when the system demand in the iterative process of development in the ever-changing needs access to sample data, the construction or reconstruction of the database prototype.3 database development of the three-tier architecture modelIn this article on the front of the database development process mentioned in the interpretation of a system development project on the establishment of the several different, but related database view or model:●conceptual model (in the analysis stage of the establishment).●external model or user view (in the analysis phase and the establishment of logical design phase).●physical model or internal model (in the physical design phase of the establishment). Figure 7 describes the database view that the relationship between the three, it is important to remember that they are the same organizations database view or model. In other words, each organization has a database of the physical model, a concept model and one or more users view. Therefore, the three-tier architecture model using the same data set observe the different ways definition database.Concept models on the full database structure, has nothing to do with the technical specifications. Conceptual model definition do not involve the entire database data stored in the computer how the secondary memory. Usually, the conceptual model by entities - links (E-R) map or object modeling symbols such a graphical format to describe, we have this type of concept model called the data model. In addition, the conceptual model specification as a metadata stored in the database or data dictionary.Physical models including conceptual model of how data stored in computer memory in the two specifications. Analysts and the database design is as important to the physical database (physical mode) definition, it provides information on the distribution and management of data storage and access of the physical memory space of two full database technology specifications.Database development and database technology database is among the three models divided into basis. Database development projects may have a role to only deal with these three views of a related work. For example, a beginner may be designed for one or more procedures external model, and an experienced developer will design the physical model or conceptual model. Database design issues at different levels are quite different.4 three-tier structure of the database positioning systemObviously, all the good things in the database are, and the "three"!When designing a database, you have to choose where to store data. This option in the physical database design stage. Database is divided into individual databases, the Working Group database, departmental databases, corporate databases and the Internet database. Individuals often by the end-user database design and development of their own, just by database experts to give training and advice to help, it only contains individual end-users interested in the data. Sometimes, personal database from the database or enterprise Working Group extracted from the database, such circumstances database prepared by some experts from the regular routine to create local database. Sector Working Group database and the database is often the end-user, business experts and the central database system experts development. The collaborative work of these officers is necessary because in the design of the database to be shared by a large number of issues weigh:processing speed, ease of use, data definition differences and other similar problems. Due to corporate databases and the Internet database broad impact, large-scale, it is normally concentrated in the database development team has received professional training to develop a database of experts.1. Customers layerA desktop or notebook also known as that layer, which specialized management user interface and system localization data in this layer can be implemented on the Web scripting tasks.2. Server / Web serverHTTP protocol handling, scripting tasks, the implementation of computing and provide data access, the layer known as processing services layer.3. Enterprise Server (Minicomputer or mainframe) layerThe implementation of complex computing and inter-organizational management from multiple data sources of data integration, also known as data services layer.In an organization, hierarchical database and information system architecture for distributed computing and the client / server architecture of the concept of correlation. Client / server architecture based on a LAN environment, including servers (referred to as database server or database engine) database software implementation from the client workstation database orders, each customer applications focus on their user interface functions. In fact, the whole concept of the database (as well as the application of these databases to handle routine) as a distributed database or the separate but related physical database distribution in the local PC workstation, server intermediate (working group or sector) and one center server (departments or enterprises ). Simply said that the use of client / server architecture for:●it can handle multiple processors on the same application at the same time, improve application response time and data processing speed.●It can use each computer platform of the best data processing (such as PC Minicom Advanced user interface with the mainframe and computing speed).●can mix various client technology (Intel or Motorola processor assembly of personal computers, computer networks, information kiosks, etc.) and public data sharing. In addition, you can change the technology at any layer and other layers only a small influence on the system module.●able to handle close to the data source to be addressed to improve response time and reduce network traffic.●accept it to allow and encourage open systems standards.For database development, the use of a multi-layered client / server database architecture development is the most meaningful of the database will be easy to develop and maintain database module to the end-user and that the contents of the database information system module separated. That routine can be used as PowerBuilder, Java, and Visual Basic language to provide this easy-to-use graphical user interface. Through middleware that routine interaction between layers can be passed to access routine, the routine visit to the necessary data and analysis of these data in order to form the required information. As a database developers and programmers, you can in this three-tier level of any of the work, developing the necessary software.外文来源Modern Database Management7 th Edition Jeffrey A. Hoffer, Mary B. Prescott, Fred R. McFadden。
数据库毕业设计外文翻译--图像系统简介
附录1 外文原文COLOR SYSTEM OVERVIEWIn the age of office automation and electronic imaging, office documents are being processed, transported, and displayed in a variety of ways. The scope of document processing is enormous; it encompasses page layout, document length, collation, simplex/duplex, color, image quality, finishing, and binding. If the office system is networked, then another dimension of network-related issues-protocol, file format, page description language, compression/decompression, job management, error handling, user interface, and device driver-has to be addressed. Digital color-imaging systems process electronic information from various sources; images may come from a local-area network, a remote-sensing device, different color workstations, or a local scanner. After processing, a document is usually compressed and transmitted to several places via a computer network for viewing, editing, or printing. Moreover, the trend in the industry is moving toward an open environment. This means that various devices such as scanners, computers, workstations, modems, and printers from multiple vendors are assembled into one system. Implementations should be based on public-domain technology rather than proprietary standards. This will allow vendors equal access to the market for system components and give users the widest choice in selecting components. It is a vastly large task to enable the communication of all system components regardless of differences in the operating system, file format, page description language, and information content. Ideally, the exchange should not cause information loss or alteration. A closer look at a document may reveal that it consists of different types of images, primarily text, graphs, and pictorial images. These all have different image characteristics and representations such as ASCII (American Standard Code for Information Interchange) for text, vector for graphs, and raster for pictorial images. Each type of image and its associated attributes like the font, font size, halftone, gray level, resolution, and color have to be dealt with differently. In such a complex environment, there is no doubt that many compatibility problems occur when an image is acquired, transmitted, displayed, and rendered. ?With the fast development of Internet technology, large volumes of data in the form of electronic documents from the Web. For the purposes of data integration and data exchange, more and moreexisting sources, such as relational databases, support public XML export, and increasing amount of public and private data is described in a semi-structured way. A number of issues need to be addressed when we integrate data from different sources, including heterogeneous and duplicate data, multiple divisions and partners, and changes.? Data heterogeneity results from the use of different information management systems to store data and each system has its own data structure and access methods. Relational database management systems benefit from the universal acceptance of Structured Query Language (SQL) as the primary means of getting answers whilst document and email repositories are generally accessed using text search engines with varying interfaces and capabilities. Because these systems were not designed with interoperability in mind, each must generally be accessed using source-specific applications or application programming interfaces (APIs).? Another difficulty in data integration is data duplication-different systems represent the same piece of data in different ways. For example, customers may be identified by name in one database, but by account number in a second repository, may identify the same customer by email address. Frequently a required piece of information is derived from multiple data points. Data integration is further complicated when customers do business with multiple divisions within a large company, or with other partners. Similarly, answering questions about the state of a company's supply chain requires access to vendor and distributor information sources. Doing business electronically across the firewall gives rise to security and data ownership issues. Finally, data integration has to deal with different types of changes; change in business requirements and strategies, in IT systems, mergers and acquisitions, and new product launches. This demands that a data integration solution be sufficiently flexible and adaptable.One possible solution for the data integration problems mentioned above is to provide an XML Web services break down the barriers between different computing platforms, development environments and communications networks, allowing organizations to work together electronically without the expense and delay of agreeing on semantics, schema, interfaces, and other application integration. XML provides the flexibility for handling data with differing structures. As XML is becoming the principal medium for data exchange over the Web and for information integration in general,increasing amounts of public and private data are described in XML. XML data is usually defined in a tree or graph based, self-describing object instance model (Boncz and Kersten, 1999). However, semi-structured data is incompatible with the flat structure of relational database tables, and so the growth of XML data requires new and complex query optimization techniques.Creating XML files with a text editor would be a lot easier if you didn't have to close all those HTML tags. First you have to add the XML declaration and the root opening and closing HTML tags. Next, you start adding element opening and closing tags one at a time. Of course, once you have the initial sequence completed you can just copy and paste to repeat the required elements. After doing this hundreds of times you'll be looking for a faster way to create XML files.Some XML editors will automatically add the closing tag after you have finished typing the opening tag but, you still have to type the brackets around the opening tag. I kept thinking this process should be easier. So, I came up with a solution that allows you to create XML files without using HTML tags.This console application will create an XML file based on user input. Just enter the file name, how many element fields you want, and the name of each field. Optionally, you can include a data type separated by a comma after the field name. You can just enter the field name because the data type is not required. The structure of the XML file that is created will be compatible with the .NET Dataset and can be easily added to a database.In addition to creating the XML file, an XSL file and HTML file are also created. The HTML file uses client side JavaScript to transform the XML file using the XSL file. This provides an easy way to view the new XML file by displaying it in a table layout.The download includes both the source code and the already compiled application. You can start using the executable right away or customize it to meet your needs. All you will need is the .NET Framework and a text editor, like Notepad, to build this application.Improving ASP Performance with Data CachingOne of the nicest features of is the ability to cache page content. This can be used to substantially reduce load on a website's database - which is an obvious attraction if the site uses Microsoft's Access to store data rather than SQL Server. Unfortunately there is no built in cachingsystem in classic ASP, but it is easy to build one by using the Application object to store data.When to use ASP Caching. Caching is most useful for data that changes - but not too often. For example an e-commerce store could display a list of popular products, or an information site could display a list of press releases.Don't forget that it is also possible to build functionality into the admin part of the site so that the cache would be flushed if new content is added to the database. That way the website administrator would not have to wait until the cache timed out in order for new content to appear on the website. Remember that data stored in Application variables is visible by all the users of the website。
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外文文献和翻译_信息系统开发和数据库开发
信息系统开发和数据库开发在许多组织中，数据库开发是从企业数据建模开始的，企业数据建模确定了组织数据库的范围和一般内容。
这一步骤通常发生在一个组织进行信息系统规划的过程中，它的目的是为组织数据创建一个整体的描述或解释，而不是设计一个特定的数据库。
一个特定的数据库为一个或多个信息系统提供数据，而企业数据模型（可能包含许多数据库）描述了由组织维护的数据的范围。
在企业数据建模时，你审查当前的系统，分析需要支持的业务领域的本质，描述需要进一步抽象的数据，并且规划一个或多个数据库开发项目。
图1显示松谷家具公司的企业数据模型的一个部分。
1.1 信息系统体系结构如图1所示，高级的数据模型仅仅是总体信息系统体系结构(ISA)一个部分或一个组织信息系统的蓝图。
在信息系统规划期间，你可以建立一个企业数据模型作为整个信息系统体系结构的一部分。
根据Zachman(1987)、Sowa和Zachman（1992）的观点，一个信息系统体系结构由以下6个关键部分组成:数据（如图1所示，但是也有其他的表示方法）。
操纵数据的处理（着系可以用数据流图、带方法的对象模型或者其他符号表示）。
网络，它在组织内并在组织与它的主要业务伙伴之间传输数据（它可以通过网络连接和拓扑图来显示）。
人，人执行处理并且是数据和信息的来源和接收者（人在过程模型中显示为数据的发送者和接收者）。
执行过程的事件和时间点（它们可以用状态转换图和其他的方式来显示）。
事件的原因和数据处理的规则（经常以文本形式显示，但是也存在一些用于规划的图表工具，如决策表）。
1.2 信息工程信息系统的规划者按照信息系统规划的特定方法开发出信息系统的体系结构。
信息工程是一种正式的和流行的方法。
信息工程是一种面向数据的创建和维护信息系统的方法。
因为信息工程是面向数据的，所以当你开始理解数据库是怎样被标识和定义时，信息工程的一种简洁的解释是非常有帮助的。
信息工程遵循自顶向下规划的方法，其中，特定的信息系统从对信息需求的广泛理解中推导出来（例如，我们需要关于顾客、产品、供应商、销售员和加工中心的数据），而不是合并许多详尽的信息请求（如一个订单输入屏幕或按照地域报告的销售汇总）。
数据库外文翻译毕业设计
Database Management Systems( 3th Edition ),Wiley ,2004,5-12A introduction to Database Management SystemRaghu RamakrishnanA database (sometimes spelled data base) is also called an electronic database , referring to any collection of data, or information, that is specially organized for rapid search and retrieval by a computer. Databases are structured to facilitate the storage, retrieval , modification, and deletion of data in conjunction with variousdata-processing operations .Databases can be stored on magnetic disk or tape, optical disk, or some other secondary storage device.A database consists of a file or a set of files. The information in these files maybe broken down into records, each of which consists of one or more fields. Fields are the basic units of data storage , and each field typically contains information pertaining to one aspect or attribute of the entity described by the database . Using keywords and various sorting commands, users can rapidly search , rearrange, group, and select the fields in many records to retrieve or create reports on particular aggregate of data.Complex data relationships and linkages may be found in all but the simplest databases .The system software package that handles the difficult tasks associated with creating ,accessing, and maintaining database records is called a database management system(DBMS).The programs in a DBMS package establish an interface between the database itself and the users of the database.. (These users may be applications programmers, managers and others with information needs, and various OS programs.)A DBMS can organize, process, and present selected data elements form the database. This capability enables decision makers to search, probe, and query database contents in order to extract answers to nonrecurring and unplanned questions that aren't available in regular reports. These questions might initially be vagueand/or poorly defined ,but people can “browse”through the database until they have the stored data items and”manage“the needed information. In short, the DBMS willassemble the needed items from the common database in response to the queries of those who aren't programmers.A database management system (DBMS) is composed of three major parts:(1)a storage subsystem that stores and retrieves data in files;(2) a modeling and manipulation subsystem that provides the means with which to organize the data and to add , delete, maintain, and update the data;(3)and an interface between the DBMS and its users. Several major trends are emerging that enhance the value and usefulnessof database management systems;Managers: who require more up-to-data information to make effective decision Customers: who demand increasingly sophisticated information services andmore current information about the status of their orders, invoices, and accounts. Users: who find that they can develop custom applications with databasesystems in a fraction of the time it takes to use traditional programming languages.Organizations : that discover information has a strategic value; they utilize their database systems to gain an edge over their competitors.The Database ModelA data model describes a way to structure and manipulate the data in a database. The structural part of the model specifies how data should be represented(such as tree, tables, and so on ).The manipulative part of the model specifies the operation with which to add, delete, display, maintain, print, search, select, sort and update the data. Hierarchical ModelThe first database management systems used a hierarchical model-that is-they arranged records into a tree structure. Some records are root records and all others have unique parent records. The structure of the tree is designed to reflect the order in which the data will be used that is ,the record at the root of a tree will be accessed first,then records one level below the root ,and so on.The hierarchical model was developed because hierarchical relationships are commonly found in business applications. As you have known, an organization char often describes a hierarchical relationship: top management is at the highest level, middle management at lower levels, and operational employees at the lowest levels. Note that within a strict hierarchy, each level of management may have many employees or levels of employees beneath it, but each employee has only one manager. Hierarchical data are characterized by this one-to-many relationship among data.In the hierarchical approach, each relationship must be explicitly defined whenthe database is created. Each record in a hierarchical database can contain only one key field and only one relationship is allowed between any two fields. This can create a problem because data do not always conform to such a strict hierarchy. Relational ModelA major breakthrough in database research occurred in 1970 when E. F. Codd proposed a fundamentally different approach to database management called relational model ,which uses a table as its data structure.The relational database is the most widely used database structure. Data is organized into related tables. Each table is made up of rows called and columns called fields. Each record contains fields of data about some specific item. For example, in a table containing information on employees, a record would contain fields of data such as a person's last name ,first name ,and street address.Structured query language(SQL)is a query language for manipulating data in a relational database .It is nonprocedural or declarative, in which the user need onlyspecify an English-like description that specifies the operation and the described record or combination of records. A query optimizer translates the description into a procedure to perform the database manipulation.Network ModelThe network model creates relationships among data through a linked-liststructure in which subordinate records can be linked to more than one parent record. This approach combines records with links, which are called pointers. The pointers are addresses that indicate the location of a record. With the network approach, a subordinate record can be linked to a key record and at the same time itself be a key record linked to other sets of subordinate records. The network mode historically has had a performance advantage over other database models. Today , such performance characteristics are only important in high-volume ,high-speed transaction processing such as automatic teller machine networks or airline reservation system.Both hierarchical and network databases are application specific. If a new application is developed ,maintaining the consistency of databases in different applications can be very difficult. For example, suppose a new pension application is developed .The data are the same, but a new database must be created.Object ModelThe newest approach to database management uses an object model , in which records are represented by entities called objects that can both store data and provide methods or procedures to perform specific tasks.The query language used for the object model is the same object-oriented programming language used to develop the database application .This can create problems because there is no simple , uniform query language such as SQL . The object model is relatively new, and only a few examples of object-oriented database exist. It has attracted attention because developers who choose an object-oriented programming language want a database based on an object-oriented model. Distributed DatabaseSimilarly , a distributed database is one in which different parts of the database reside on physically separated computers . One goal of distributed databases is the access of information without regard to where the data might be stored. Keeping in mind that once the users and their data are separated , the communication and networking concepts come into play .Distributed databases require software that resides partially in the larger computer. This software bridges the gap between personal and large computers and resolves the problems of incompatible data formats. Ideally, it would make the mainframe databases appear to be large libraries of information, with most of the processing accomplished on the personal computer.A drawback to some distributed systems is that they are often based on what is called a mainframe-entire model , in which the larger host computer is seen as the master and the terminal or personal computer is seen as a slave. There are some advantages to this approach . With databases under centralized control , many of the s personal'problems of data integrity that we mentioned earlier are solved . But todaycomputers, departmental computers, and distributed processing require computers and their applications to communicate with each other on a more equal or peer-to-peer basis. In a database, the client/server model provides the framework for distributing databases.One way to take advantage of many connected computers running database applications is to distribute the application into cooperating parts that are independent of one anther. A client is an end user or computer program that requests resources across a network. A server is a computer running software that fulfills those requests across a network . When the resources are data in a database ,the client/server model provides the framework for distributing database.A file serve is software that provides access to files across a network. Adedicated file server is a single computer dedicated to being a file server. This is useful ,for example ,if the files are large and require fast access .In such cases, a minicomputer or mainframe would be used as a file server. A distributed file server spreads the files around on individual computers instead of placing them on one dedicated computer.Advantages of the latter server include the ability to store and retrieve files onother computers and the elimination of duplicate files on each computer. A major disadvantage , however, is that individual read/write requests are being moved across the network and problems can arise when updating files. Suppose a user requests a record from a file and changes it while another user requests the same record and changes it too. The solution to this problems called record locking, which means that the first request makes others requests wait until the first request is satisfied . Other users may be able to read the record, but they will not be able to change it .A database server is software that services requests to a database across a network. For example, suppose a user types in a query for data on his or her personal computer . If the application is designed with the client/server model in mind ,the query language part on the personal computer simple sends the query across the network to the database server and requests to be notified when the data are found. Examples of distributed database systems can be found in the engineering world. Sun's Network Filing System(NFS),for example, is used in computer-aided engineering applications to distribute data among the hard disks in a network of Sun workstation.Distributing databases is an evolutionary step because it is logical that datashould exist at the location where they are being used . Departmental computers within a large corporation ,for example, should have data reside locally , yet those data should be accessible by authorized corporate management when they want to consolidate departmental data . DBMS software will protect the security and integrity of the database , and the distributed database will appear to its users as no different from the non-distributed database .。