數(shù)據(jù)庫相關(guān)畢業(yè)設(shè)計外文翻譯

1、 database management systems（dbms）and management information system（mis）you know that a database is a collection of logically related data elements that may be structured in various ways to meet the multiple processing and retrieval needs of organizations and individualsthere s nothing new about dat

2、abasesearly ones1 were chiseled in stone，penned on scrolls，and written on index cardsbut now databases are commonly recorded on magnetizable media，and computer programs are required to perform the necessary storage and retrieval operationsyoull see in the following pages that complex data relationsh

3、ips and linkages may be found in all but the simplest databases2the 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 t

4、he 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 from the databasethis capability enables decision makers to search，probe，and

5、query database contents in order to extract answers to nonrecurring and unplanned questions that arent available in regular reports3these questions might initially be vague and / or poorly defined，but people can“browse”through the database until they have the needed informationin short，the dbms will

6、“manage”the stored data items and assemble the needed items from the common database in response to the queries of those who arent programmersin a file-oriented system，users needing special information may communicate their needs to a programmer，who，when time permits，will write one or more programs

7、to extract the data and prepare the information4the availability of a dbms，however，offers users a much faster alternative communications path（see fig. 7-1）if the dbms provides a way to interactively and update the database, as well as interrogate it capability allows for managing personal data-aces

8、however, it does not automatically leave an audit trail of actions and does not provide the kinds of controla necessary in a multiuser organization. these-controls are only available when a set of application programs are customized for each data entry and updating function. software for personal co

9、mputers which perform me of the dbms functions have been very popular arsenal computers were intended for use by individuals for personal information storage and process- these machines have also been used extensively small enterprises, professionals like doctors, acrylics, engineers, lawyers and so

10、 on by the nature of. intended usage, database systems on these machines except from several of the requirements of full doge database systemssince data sharing is not：tended, concurrent operations even less so, the) fewer can be less complex. security and integrity7aintenance are de-emphasized or a

11、bsent. as data-) limes will be small, performance efficiency is also important. in fact, the only aspect of a database system that is important is data independence. data-.dependence, as stated earlier. means that applicant programs and user queries need not recognizantphysical organization of data

12、on secondary storage. the importance of this aspect, particularly for the personal computer user, is that this greatly simplifies database usage. the user can store, access and manipulate data at a high level (close to the application) and be totally shielded from the low level (close to the machine

13、) details of data organization. we will not discuss details of specific pc dbms software packages herelet us summarize in the following the strengths and weaknesses of personal computer data-base software systems： the most obvious positive factor is the user friendliness of the software. a user with

14、 no prior computer background would be able to use the system to store personal and professional data, retrieve and perform relayed processing. the user should, of course, satiety himself about the quality of software and the freedom from errors (bugs) so that invest-merits in data arc protected. fo

15、r the programmer implementing applications with them, the advantage lies in the support for applications development in terms of input screen generations, output report generation etcoffered by theses stems the main negative point concerns absence of data protection featuresunless encrypted, data ca

16、ne accessed by whoever has access to the machine data can be destroyed through mistakes or maliciousintent. the second weakness of manv of the pc-basedsystems is that of performance. if data volumes growup to a few thousands of records，performance couldbe a bottleneck for organization where growth i

17、n data volumesis expected, availability of, the same or compatiblesoftware on large machines should be considered.this is one of the most common misconceptionsabout database management systems that are used inpersonal computersthoroughly comprehensive andsophisticated business systems can be develop

18、ed indbash, paradox and other dbmsshowever, theyare created by experienced programmers using thedbmss own programming language. that is not the same as users who create and manage personal filesthat are not part of the mainstream company systemtransaction management of databasethe objective of long-

19、duration transactions is to model long-duration, interactive database access sessions in application environmentsthe fundamental assumption about short-duration of transactions that underlies the traditional model of transactions is inappropriate for long-duration transactionsthe implementation of t

20、he traditional model of transactions may cause intolerably long waits when transactions aleph to acquire locks before accessing data, and may also cause a large amount of work to be lost when transactions are backed out in response to user-initiated aborts or system failure situations the objective

21、of a transaction model is to pro-vide a rigorous basis for automatically enforcing criterion for database consistency for a set of multiple concurrent read and write accesses to the database in the presence of potential system failure situationsthe consistency criterion adopted for traditional trans

22、actions is the notion of scrializabilityscrializa-bility is enforced in conventional database systems through the use of locking for automatic concurrency control, and logging for automatic recovery from system failure situationsa transaction”that doesnt provide a basis for automatically enforcing d

23、ata-base consistency is not really a transaction. to be sure, a long-duration transaction need not adopt seri-alizability as its consistency criterionhowever. there must be some consistcricv criterionversion system management of database despite a large number of proposals on version support in the

24、context of computer aided design and software engineering, the absence of a consensus on version semantics has been a key impediment to version support in database systemsbecause of the differences between files and databases, it is intuitively clear that the model of versions in database systems ca

25、nnot be as simple as that adopted in file systems to support software engineeringfor data-bases, it may be necessary to manage not only versions of single objects (e.g. a software module, document, but also versions of a collection of objects (e.g. a compound document, a user manual，etcand perhaps e

26、ven versions of the schema of database (c.g. a table or a class, a collection of tables or classes) broadly, there are three directions of research and development in versioningfirst is the notion of a parameterized versioning，that is, designing and implementing a versioning system whose behavior ma

27、y be tailored by adjusting system parameters this may be the only viable approach, in view of the fact that there are various plausible choices for virtually every single aspect of versioningthe second is to revisit these plausible choices for every aspect of versioning, with the view to discarding

28、some of themes either impractical or flawed. the third is the investigation into the semantics and implementation of versioning collections of objects and of versioning the database sche there is no consensus of the definition of the term management information system. some writers prefer alternativ

29、e terminology such as information processing system, information and decision system, organizational information system, or simply information system to refer to the computer-based information processing system which supports the operations, management, and decision-making functions of an organizati

30、on. this text uses “mis” because it is descriptive and generally understood; it also frequently uses “information system” instead of “mis” to refer to an organizational information system.2、a definition of a management information system, as the term is generally understood, is an integrated, user-m

31、achine system for providing information to support operations, management, and decision-making functions in an organization. the system utilizes computer hardware and software; manual procedures; models for analysis planning, control and decision making; and a database. the fact that it is an integr

32、ated system does not mean that it is a single, monolithic structure; rather, it means that the parts fit into an overall design. the elements of the definition are highlighted below. computer-based user-machine system3、conceptually, a management information can exist without computer, but it is the

33、power of the computer which makes mis feasible. the question is not whether computers should be used in management information system, but the extent to which information use should be computerized. the concept of a user-machine system implies that some tasks are best performed by humans, while othe

34、rs are best done by machine. the user of an mis is any person responsible for entering input data, instructing the system, or utilizing the information output of the system. for many problems, the user and the computer form a combined system with results obtained through a set of interactions betwee

35、n the computer and the user.4、user-machine interaction is facilitated by operation in which the users input-output device( usually a visual display terminal) is connected to the computer. the computer can be a personal computer serving only one user or a large computer that serves a number of users

36、through terminals connected by communication lines. the user input-output device permits direct input of data and immediate output of results. for instance, a person using the computer interactively in financial planning poses “what if” questions by entering input at the terminal keyboard; the resul

37、ts are displayed on the screen in a few second.5、the computer-based user-machine characteristics of an mis affect the knowledge requirements of both system developer and system user. “computer-based” means that the designer of a management information system must have a knowledge of computers and of

38、 their use in processing. the “user-machine” concept means the system designer should also understand the capabilities of humans as system components (as information processors) and the behavior of humans as users of information.6、information system applications should not require users to be comput

39、er experts. however, users need to be able to specify their information requirements; some understanding of computers, the nature of information, and its use in various management function aids users in this task.integrated system集成系統(tǒng)7、management information system typically provide the basis for in

40、tegration of organizational information processing. individual applications within information systems are developed for and by diverse sets of users. if there are no integrating processes and mechanisms, the individual applications may be inconsistent and incompatible. data item may be specified di

41、fferently and may not be compatible across applications that use the same data. there may be redundant development of separate applications when actually a single application could serve more than one need. a user wanting to perform analysis using data from two different applications may find the ta

42、sk very difficult and sometimes impossible.8、the first step in integration of information system applications is an overall information system plan. even though application systems are implemented one at a time, their design can be guided by the overall plan, which determines how they fit in with ot

43、her functions. in essence, the information system is designed as a planed federation of small systems.9、information system integration is also achieved through standards, guidelines, and procedures set by the mis function. the enforcement of such standards and procedures permit diverse applications

44、to share data, meet audit and control requirements, and be shares by multiple users. for instance, an application may be developed to run on a particular small computer. standards for integration may dictate that the equipment selected be compatible with the centralized database. the trend in inform

45、ation system design is toward separate application processing form the data used to support it. the separate database is the mechanism by which data items are integrated across many applications and made consistently available to a variety of users. the need for a database in mis is discussed below.

46、need for a database 10、 the term “information” and “data” are frequently used interchangeably; however, information is generally defined as data that is meaningful or useful to the recipient. data items are therefore the raw material for producing information.11、the underlying concept of a database

47、is that data needs to be managed in order to be available for processing and have appropriate quality. this data management includes both software and organization. the software to create and manage a database is a database management system.12、when all access to any use of database is controlled th

48、rough a database management system, all applications utilizing a particular data item access the same data item which is stored in only one place. a single updating of the data item updates it for all uses. integration through a database management system requires a central authority for the databas

49、e. the data can be stored in one central computer or dispersed among several computers; the overriding requirement is that there be an organizational function to exercise control.utilization of models 13、it is usually insufficient for human recipients to receive only raw data or even summarized data

50、. data usually needs to be processed and presented in such a way that the result is directed toward the decision to be made. to do this, processing of data items is based on a decision model. for example, an investment decision relative to new capital expenditures might be processed in terms of a ca

51、pital expenditure decision model. 14、decision models can be used to support different stages in the decision-making process. “intelligence” models can be used to search for problems and/or opportunities. models can be used to identify and analyze possible solutions. choice models such as optimizatio

52、n models maybe used to find the most desirable solution.15、in other words, multiple approaches are needed to meet a variety of decision situations. the following are examples and the type of model that might be included in an mis to aid in analysis in support of decision-making; in a comprehensive i

53、nformation system, the decision maker has available a set of general models that can be applied to many analysis and decision situations plus a set of very specific models for unique decisions. similar models are available for planning and control. the set of models is the model base for the mis.16、

54、models are generally most effective when the manager can use interactive dialog to build a plan or to iterate through several decision choices under different conditions.眾所周知，數(shù)據(jù)庫是邏輯上相關(guān)的數(shù)據(jù)元的匯集。這些數(shù)據(jù)元可以按不同的結(jié)構(gòu)組織起來，以滿足單位和個人的多種處理和檢索的需要。數(shù)據(jù)庫本身不是什么新鮮事一早期的數(shù)據(jù)庫鑿在石頭上，記在名冊上，以及寫在索引卡中。而現(xiàn)在，數(shù)據(jù)庫普遍記錄在可磁化的介質(zhì)上，并且需要用計算機(jī)程序

55、來執(zhí)行必需的存儲和檢索操作。如下所述，所有數(shù)據(jù)庫（最簡單的除外）中都有復(fù)雜的數(shù)據(jù)關(guān)系及其鏈接。處理與創(chuàng)建、訪問以及維護(hù)數(shù)據(jù)庫記錄有關(guān)的復(fù)雜任務(wù)的系統(tǒng)軟件包叫做數(shù)據(jù)庫管理系統(tǒng)（dbms）。dbms軟件包中的程序在數(shù)據(jù)庫與其用戶間建立接口。（這些用戶可以是應(yīng)用程序員、管理員、及其他需要信息的人員和各種操作系統(tǒng)程序）。dbms可組織、處理和表示從數(shù)據(jù)庫中選出的數(shù)據(jù)元。該功能使決策者能搜索、探查和查詢數(shù)據(jù)庫的內(nèi)容，從而對在正規(guī)報告中沒有的、不再出現(xiàn)的且無法預(yù)料的問題作出回答。這些問題最初可能是模糊的并且（或者）是定義不恰當(dāng)?shù)模侨藗兛梢詾g覽數(shù)據(jù)庫直到獲得所需的信息。簡言之，dbms將“管理”存儲的數(shù)

56、據(jù)項(xiàng)，并從公共數(shù)據(jù)庫中匯集所需的數(shù)據(jù)項(xiàng)以回答非程序員的詢問。在面向文件的系統(tǒng)中，需要特定信息的用戶應(yīng)將他們的要求傳送給程序員。該程序員在時間允許時，將編寫一個或多個程序以提取數(shù)據(jù)和準(zhǔn)備信息。然而，dbms的可用性為用戶提供了一個更快的替代通信通道（如圖7-1所示）。如果數(shù)據(jù)庫管理系統(tǒng)提供一種方法來相互作用地進(jìn)入和修改數(shù)據(jù)庫，同時查詢數(shù)據(jù)庫，這種方法就為管理個人數(shù)據(jù)庫創(chuàng)造了條件。但是，它不能自動留下一串查賬行動，也不能在多用戶組織中提供那種必要的控制。只有當(dāng)一套應(yīng)用程序?yàn)槊恳粋€數(shù)據(jù)進(jìn)入和修改功能設(shè)定客戶規(guī)格時，才有可能得到這些控制。當(dāng)前，執(zhí)行數(shù)據(jù)庫系的一些功能的個人計算機(jī)軟件一直很流行。個人計算

57、機(jī)是供個人信息存儲和處理而用。這些機(jī)器也廣泛地被一些小企業(yè)、職業(yè)家如建筑師，醫(yī)師、工程師、律師等等所使用。從使用意圖的性質(zhì)看，這些機(jī)器上的數(shù)據(jù)庫系統(tǒng)沒有正式數(shù)據(jù)庫系統(tǒng)的一些要求。由于不需要數(shù)據(jù)分享，也不需要同時操作。軟件也就不那么復(fù)雜。安全和整體維護(hù)也不那么重要，甚至沒有隨著數(shù)據(jù)容量變性能效率也不那么重要。事實(shí)上，數(shù)據(jù)庫系統(tǒng)唯一重要的方面是數(shù)據(jù)獨(dú)立。正如以前所述，數(shù)據(jù)獨(dú)立是指在輔助存儲器上，應(yīng)用程序和用戶詢問不必知道數(shù)排的物理組織。這個方面的重要性，尤其對個人計算機(jī)用戶來說，大大簡化了數(shù)據(jù)庫的使用。用戶能夠高層次地存儲，存取和操縱數(shù)據(jù)，并且能夠完全不受數(shù)據(jù)組織低層次細(xì)節(jié)的影響。在這里我們將不討

58、論一個特定個人計算機(jī)數(shù)據(jù)庫管理系統(tǒng)軟件包細(xì)節(jié)。我們將在下面總結(jié)一下個人計算機(jī)數(shù)據(jù)庫軟件系統(tǒng)的優(yōu)缺點(diǎn)：最明顯的積極方面是軟件的用戶友好型。一個事先不了解計算機(jī)知識的用戶能夠使用該系統(tǒng)來儲存?zhèn)€人和職業(yè)數(shù)據(jù)，檢索和執(zhí)行有關(guān)處理。當(dāng)然，用戶應(yīng)該使自己對軟件質(zhì)量感到滿足，高質(zhì)量的軟件仗數(shù)據(jù)的出錯率減少從而使數(shù)據(jù)投資 得到保護(hù)。對于完成應(yīng)用的程序員而言，這個優(yōu)點(diǎn)存在于支持這些系統(tǒng)所提供的在輸入屏幕產(chǎn)生，輸出報告產(chǎn)生方面的應(yīng)用發(fā)展。主要消極點(diǎn)是缺少數(shù)據(jù)保護(hù)特征。除非被譯成密碼，數(shù)據(jù)不能被任何接觸機(jī)器的人所存取。數(shù)據(jù)也能由于錯誤或被懷有惡意的人毀掉。以個人計算機(jī)為基礎(chǔ)的許多系 統(tǒng)的第二個缺點(diǎn)是效率方面的缺點(diǎn)。如果數(shù)據(jù)發(fā)展到幾千個記錄，效率問題可能是一個難關(guān)。 由于數(shù)據(jù)容量的增長是一種發(fā)展趨勢，所以應(yīng)該考慮在較大的權(quán)器上獲得相同或相容的軟件。這是對用個人計算機(jī)數(shù)據(jù)庫管理系統(tǒng)的最常見的錯誤概念之一：高綜合和復(fù)雜的商業(yè)系統(tǒng)可以在dbase，paradox和其它數(shù)據(jù)庫譽(yù)理系統(tǒng)中得以發(fā)展。但是，這些商業(yè)系統(tǒng)是由富有經(jīng)驗(yàn)的程序設(shè)計員通過使用數(shù)據(jù)庫管理系統(tǒng)專用的程序語言而建立的，這與建立和管理不是公司主要系統(tǒng)部分的個人文件的用戶有所不同。1. 數(shù)據(jù)庫的業(yè)務(wù)管理長期業(yè)務(wù)的目的是：在應(yīng)用環(huán)境中模擬長期的、相互作用的數(shù)據(jù)庫存取對話傳統(tǒng)業(yè)務(wù)模式中關(guān)于短期業(yè)務(wù)的基本假設(shè)對于