软件工程外文翻译
软件工程(外文翻译文献)
外文文献资料1、Software EngineeringSoftware is the sequences of instructions in one or more programming languages that comprise a computer application to automate some business function. Engineering is the use of tools and techniques in problem solving. Putting the two words together, software engineering is the systemtic application of tools and techniques in the development of computer-based applications.The software engineering process describes the steps it takes to deelop the system. We begin a development project with the notion that there is a problem to be solved via automation. The process is how you get from problem recognition to a working solution. A quality process is desirable because it is more likely to lead to a quality product. The process followed by a project team during the development life cycle of an application should be orderly, goal-oriented, enjoyable, and a learning experience.Object-oriented methodology is an approach to system lifecycle development that takes a top-down view of data objects, their allowable actions, and the underlying communication requirement to define a system architecture. The data and action components are encapsulated, that is , they are combined together, to form abstract data types Encapsulation means that if I know what data I want ,I also know the allowable processes against that data. Data are designed as lattice hierarchies of relationships to ensure that top-down, hierarchic inheritance and side ways relationships are accommodated. Encapsulated objects are constrained only to communicate via messages. At a minimum, messages indicate the receiver and action requested. Messages may be more elaborate, including the sender and data to be acted upon.That we try to apply engineering discipline to software development does not mean that we have all the answers about how to build applications. On the contrary, we still build systems that are not useful and thus are not used. Part of the reason for continuing problems in application development, is that we are constantly trying to hita moving target. Both the technology and the type of applications needed by businesses are constantly changing and becoming more complex. Our ability to develop and disseminate knowledge about how to successfully build systems for new technologies and new application types seriously lags behind technological and business changes.Another reason for continuing problems in application development is that we aren’t always free to do what we like and it is hard to change habits and cultures from the old way of doing things, as well as get users to agree with a new sequence of events or an unfamiliar format for documentation.You might ask then, if many organizations don’t use good software engineering practices, why should I bother learning them? There are two good answers to this question. First, if you never know the right thing to do, you have no chance of ever using it. Second, organizations will frequently accept evolutionary, small steps of change instead of revolutionary, massive change. You can learn individual techniques that can be applied without complete devotion to one way of developing systems. In this way, software engineering can speed changee in their organizations by demonstrating how the tools and techniques enhance th quality of both the product and the process of building a system.2、Data Base System1、IntroductionThe development of corporate databases will be one of the most important data-processing activities for the rest of the 1970s. Date will be increasingly regarded as a vital corporate resource, which must be organized so as to maximize their value. In addition to the databases within an organization, a vast new demand is growing for database services, which will collect, organize, and sell data.The files of data which computers can use are growing at a staggering rate. The growth rate in the size of computer storage is greater than the growth in the size or power of any other component in the exploding data processing industry. The more data the computers have access to, the greater is their potential power. In all walks of life and in all areas of industry, data banks will change the areas of what it is possiblefor man to do. In the end of this century, historians will look back to the coming of computer data banks and their associated facilities as a step which changed the nature of the evolution of society, perhaps eventually having a greater effect on the human condition than even the invention of the printing press.Some most impressive corporate growth stories of the generation are largely attributable to the explosive growth in the need of information.The vast majority of this information is not yet computerized. However, the cost of data storage hardware is dropping more rapidly than other costs in data processing. It will become cheaper to store data on computer files than to store them on paper. Not only printed information will be stored. The computer industry is improving its capability to store line drawing, data in facsimile form, photo-graphs, human speech, etc. In fact, any form of information other than the most intimate communications between humans can be transmitted and stored digitally.There are two main technology developments likely to become available in the near future. First, there are electromagnetic devices that will hold much more data than disks but have much longer access time. Second, there are solid-state technologies that will give microsecond access time but capacities are smaller than disks.Disks themselves may be increased in capacity somewhat. For the longer term future there are a number of new technologies which are currently working in research labs which may replace disks and may provide very large microsecond-access-time devices. A steady stream of new storage devices is thus likely to reach the marketplace over the next 5 years, rapidly lowering the cost of storing data.Given the available technologies, it is likely that on-line data bases will use two or three levels of storage. One solid-state with microsecond access time, one electromagnetic with access time of a fraction of a second. If two ,three ,or four levels of storage are used, physical storage organization will become more complex ,probably with paging mechanisms to move data between the levels; solid-state storage offers the possibility of parallel search operation and associativememory.Both the quantity of data stored and the complexity of their organization are going up by leaps and bounds. The first trillion bit on-line stores are now in use . in a few year’s time ,stores of this size may be common.A particularly important consideration in data base design is to store the data so that the can be used for a wide variety of applications and so that the way they can be changed quickly and easily. On computer installation prior to the data base era it has been remarkably difficult to change the way data are used. Different programmers view the data in different ways and constantly want to modify them as new needs arise modification , however ,can set off a chain reaction of changes to existing programs and hence can be exceedingly expensive to accomplish .Consequently , data processing has tended to become frozen into its old data structures .To achieve flexibility of data usage that is essential in most commercial situations . Two aspects of data base design are important. First, it should be possible to interrogate and search the data base without the lengthy operation of writing programs in conventional programming languages. Second ,the data should be independent of the programs which use them so that they can be added to or restructured without the programs being changed .The work of designing a data base is becoming increasing difficult , especially if it is to perform in an optimal fashion . There are many different ways in which data can be structured ,and they have different types of data need to be organized in different ways. Different data have different characteristics , which ought to effect the data organization ,and different users have fundamentally different requirements. So we need a kind of data base management system(DBMS)to manage data.Data base design using the entity-relationship model begins with a list of the entity types involved and the relationships among them. The philosophy of assuming that the designer knows what the entity types are at the outset is significantly different from the philosophy behind the normalization-based approach.The entity-relationship(E-R)approach uses entity-relationship diagrams. The E-Rapproach requires several steps to produre a structure that is acceptable by the particular DBMS. These steps are:(1) Data analysis(2) Producing and optimizing the entity model.(3) Logical schema development(4) Physical data base design process.Developing a data base structure from user requirements is called data bases design. Most practitioners agree that there are two separate phases to the data base design process. The design of a logical database structure that is processable by the data base management system(DBMS)d escribes the user’s view of data, and is the selection of a physical structure such as the indexed sequential or direct access method of the intended DBMS.Current data base design technology shows many residual effects of its outgrowth from single-record file design methods. File design is primarily application program dependent since the data has been defined and structured in terms of individual applications to use them. The advent of DBMS revised the emphasis in data and program design approaches.There are many interlocking questions in the design of data-base systems and many types of technique that one can use is answer to the question so many; in fact, that one often sees valuable approaches being overlooked in the design and vital questions not being asked.There will soon be new storage devices, new software techniques, and new types of data bases. The details will change, but most of the principles will remain. Therefore, the reader should concentrate on the principles.2、Data base systemThe conception used for describing files and data bases has varied substantially in the same organization.A data base may be defined as a collection of interrelated data stored together with as little redundancy as possible to serve on or more applications in an optimal fashion; the data are stored so that they are independent of programs which use thedata; 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 data bases if they are entirely separate in structure.A data base may be designed for batch processing, real-time processing, or in-line processing. A data base system involve application program, DBMS, and data base.One of the most important characteristics of most data bases is that they will constantly need to change and grow. Easy restructuring of the data base must be possible as new data types and new applications are added. 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 data base can be changed will have a major effect on the rate at which data-processing application can be developed in a corporation.The term data independence is often quoted as being one of the main attributes of a data base. It implies that the data and the application programs which use them are independent so that either may be changed without changing the other. When a single set of data items serves a variety of applications, different application programs perceive different relationships between the data items. To a large extent, data-base organization is concerned with the representation of relationship between data items and records as well as how and where the data are stored. A data base used for many applications can have multiple interconnections between the data item about which we may wish to record. It can describes the real world. The data item represents an attribute, and the attribute must be associated with the relevant entity. We design values to the attributes, one attribute has a special significance in that it identifies the entity.An attribute or set of attribute which the computer uses to identify a record or tuple is referred to as a key. The primary key is defined as that key used to uniquely identify one record or tuple. The primary key is of great importance because it is used by the computer in locating the record or tuple by means of an index or addressing algorithm.If the function of a data base were merely to store data, its organization would be simple. Most of the complexities arise from the fact that is must also show the relationships between the various items of data that are stored. It is different to describe the data in logical or physical.The logical data base description is referred to as a schema .A schema is a chart of the types of data that one used. It gives the names of the entities and attributes, and specifics the relations between them. It is a framework into which the values of the data-items can be fitted.We must distinguish between a record type and a instance of the record. When we talk about a “personnel record”,this is really a record type.There are no data values associated with it.The term schema is used to mean an overall chart of all of the dataitem types and record types stored in a data he uses. Many different subschema can be derived from one schema.The schema and the subschema are both used by the data-base management system, the primary function of which is to serve the application programs by executing their data operations.A DBMS will usually be handing 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 data definition language is a high-level language, enabling one to describe the conceptual schema in terms of a “data model” .The choice of a data model is a difficult one, since it must be rich 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 schema by a physical schema. It should be emphasized that while a DBMS might be used to build small data bases, many data bases involve millions of bytes, and an inefficient implementation can be disastrous.We will discuss the data model in the following.3、Three Data ModelsLogical schemas are defined as data models 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 :RelationalHierarchicalNetworkThe hierarchical and network structures have been used for DBMS since the 1960s. The relational structure was introduced in the early 1970s.In the relational model, the entities and their relationships are represented by two-dimensional tables. Every table represents an entity and is made up of rows and columns. Relationships between entities are represented by common columns containing identical values from a domain or range of possible values.The last user is presented with a simple data model. His and her request are formulated in terms of the information content and do not reflect any complexities due to system-oriented aspects. A relational data model is what the user sees, but it is not necessarily what will be implemented physically.The relational data model removes the details of storage structure and access strategy from the user interface. The model provides a relatively higher degree of data. To be able 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 on a tree-like structure made up of nodes and branches. A node is a collection of data attributes describing the entity at that point.The highest node of the hierarchical tree structure is called a root. The nodes at succeeding lower levels are called children .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 node in the preceding 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 node is accessible only through its parent node, the many-to –many relationship can be implemented 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 data base consists of a number of areas. An area contains records. In turn, a record 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 real life can be implemented easily. The network data model is very complex, the application programmer must be familiar with the logical structure of the data base.4、Logical Design and Physical DesignLogical design of databases is mainly concerned with superimposing the constructs of the data base management system on the logical data model. There are three mainly models: hierarchical, relational, network we have mentioned above.The physical model is a framework of the database to be stored on physical devices. The model must be constructed with every regard given to the performance of the resulting database. One should carry out an analysis of the physical model with average frequencies of occurrences of the grou pings of the data elements, with expected space estimates, and with respect to time estimates for retrieving and maintaining the data.The database designer may find it necessary to have multiple entry points into a database, or to access a particular segment type with more than one key. To provide this type of access; it may be necessary to invert the segment on the keys. Thephysical designer must have expertise in knowledge of the DBMS functions and understanding of the characteristics of direct access devices and knowledge of the applications.Many data bases have links between one record and another, called pointers. A pointer is a field in one record which indicates where a second record is located on the storage devices.Records that exist on storage devices is a given physical sequence. This sequencing may be employed for some purpose. The most common pupose is that records are needed in a given sequence by certain data-processing operations and so they are stored in that sequences.Different applications may need records in different sequences.The most common method of ordering records is to have them in sequence by a key —that key which is most commonly used for addressing them. An index is required to find any record without a lengthy search of the file.If the data records are laid out sequentially by key, the index for that key can be much smaller than they are nonsequential.Hashing has been used for addressing random-access storages since they first came into existence in the mid-1950s. But nobody had the temerity to use the word hashing until 1968.Many systems analysis has avoided the use of hashing in the suspicion that it is complicated. In fact, it is simple to use and has two important advantages over indexing. First, it finds most records with only one seek and second, insertion and deletions can be handled without added complexity. Indexing, however, can be used with a file which is sequential by prime key and this is an overriding advantage, for some batch-pro-cessing applications.Many data-base systems use chains to interconnect records also. A chain refers to a group of records scatters within the files and interconnected by a sequence of pointers. The software that is used to retrive the chained records will make them appear to the application programmer as a contiguous logical file.The primary disadvantage of chained records is that many read operations areneeded in order to follow lengthy chains. Sometimes this does not matter because the records have to be read anyway. In most search operations, however, the chains have to be followed through records which would not otherwise to read. In some file organizations the chains can be contained within blocked physical records so that excessive reads do not occur.Rings have been used in many file organizations. They are used to eliminate redundancy. When a ring or a chain is entered at a point some distance from its head, it may be desirable to obtain the information at the head quickly without stepping through all the intervening links.5、Data Description LanguagesIt is necessary for both the programmers and the data administrator to be able to describe their data precisely; they do so by means of data description languages. A data description language is the means of declaring to data-base management system what data structures will be used.A data description languages giving a logical data description should perform the folloeing functions:It should give a unique name to each data-item type, file type, data base and other data subdivision.It should identify the types of data subdivision such as data item segment , record and base file.It may define the type of encoding the program uses in the data items (binary , character ,bit string , etc.)It may define the length of the data items and the range of the values that a data item can assume .It may specify the sequence of records in a file or the sequence of groups of record in the data base .It may specify means of checking for errors in the data .It may specify privacy locks for preventing unauthorized reading or modification of the data .These may operate at the data-item ,segment ,record, file or data-base level and if necessary may be extended to the contents(value) of individual data items .The authorization may , on the other hand, be separate defined .It is more subject to change than the data structures, and changes in authorization proceduresshould not force changes in application programs.A logical data description should not specify addressing ,indexing ,or searching techniques or specify the placement of data on the storage units ,because these topics are in the domain of physical ,not logical organization .It may give an indication of how the data will be used or of searching requirement .So that the physical technique can be selected optimally but such indications should not be logically limiting.Most DBMS have their own languages for defining the schemas that are used . In most cases these data description languages are different to other programmer language, because other programmer do not have the capability to define to variety of relationship that may exit in the schemas.附录 B 外文译文1、软件工程软件是指令的序列，该指令序列由一种或者多种程序语言编写，它能使计算机应用于某些事物的运用自动化。
软件工程毕业论文文献翻译中英文对照
软件工程毕业论文文献翻译中英文对照学生毕业设计(论文)外文译文学生姓名: 学号专业名称:软件工程译文标题(中英文):Qt Creator白皮书(Qt Creator Whitepaper)译文出处:Qt network 指导教师审阅签名: 外文译文正文:Qt Creator白皮书Qt Creator是一个完整的集成开发环境(IDE)，用于创建Qt应用程序框架的应用。
Qt是专为应用程序和用户界面，一次开发和部署跨多个桌面和移动操作系统。
本文提供了一个推出的Qt Creator和提供Qt开发人员在应用开发生命周期的特点。
Qt Creator的简介Qt Creator的主要优点之一是它允许一个开发团队共享一个项目不同的开发平台(微软Windows?的Mac OS X?和Linux?)共同为开发和调试工具。
Qt Creator的主要目标是满足Qt开发人员正在寻找简单，易用性，生产力，可扩展性和开放的发展需要，而旨在降低进入新来乍到Qt的屏障。
Qt Creator 的主要功能，让开发商完成以下任务: , 快速，轻松地开始使用Qt应用开发项目向导，快速访问最近的项目和会议。
, 设计Qt物件为基础的应用与集成的编辑器的用户界面，Qt Designer中。
, 开发与应用的先进的C + +代码编辑器，提供新的强大的功能完成的代码片段，重构代码，查看文件的轮廓(即，象征着一个文件层次)。
, 建立，运行和部署Qt项目，目标多个桌面和移动平台，如微软Windows，Mac OS X中，Linux的，诺基亚的MeeGo，和Maemo。
, GNU和CDB使用Qt类结构的认识，增加了图形用户界面的调试器的调试。
, 使用代码分析工具，以检查你的应用程序中的内存管理问题。
, 应用程序部署到移动设备的MeeGo，为Symbian和Maemo设备创建应用程序安装包，可以在Ovi商店和其他渠道发布的。
, 轻松地访问信息集成的上下文敏感的Qt帮助系统。
软件工程(中英对照课件精品)第九章
Techniques used in system testing系统测试使用的技术
Build or spin plan for gradual testing构建或螺 旋化渐进测试计划 Configuration management配置管理
versions and releases版本和发布 production system vs. development system产 品系统与开发系统 deltas, separate files and conditional compilation差别文件、单独文件和条件编译 change control变动控制
Separate the requirement into five ―cause‖这些需求分成5 种“原因” 1. 函数名为 “LEVEL‖ 2. 参数体“(A, B)‖ 3. 函数值= LOW 4. 函数值= SAFE 5. 函数值= HIGH Three ―effects‖三种“结果” 1. 显示 “LEVEL = SAFE‖ 2. 显示 “LEVEL = HIGH‖ 3. 显示 “INVALID SYNTAX‖ 为函数体的语法检查增加两个中间节点 1. The command is syntactically valid命令是合法的 2. The operands are syntactically valid操作数是合法的
Function testing功能测试: does the integrated system perform as promised by the requirements specification系统能按需求规格说 明的要求运行吗? Performance testing性能测试: are the nonfunctional requirements met是需求说明中的非 功能需求? Acceptance testing验收测试: is the system what the customer expects是客户所希望的系 统? Installation testing安装测试: does the system run at the customer site(s)系统能运行在客户的 环境吗?
软件工程专业外文翻译
软件工程专业外文翻译英文原文SSH is Spring + struts + Hibernate an integration framework, is one of the more popular a Web application framework・SpringLight weight 一一from two aspects in terms of size and cost of the Spring are lightweight・A complete Spring framework can in one size only1MB multiple JAR files released .And Spring required processing overhead is not worth mentioning・Inversion of control 一一Spring through a known as inversion of control (IoC) technology promotes loose coupling .When using IoC, an object depend on other objects will be passed in through passive way, but not the object of its own to create or find a dependent object .You can think of IoC and JNDI instead 一一not the object from the container for dependent, but in different container object is initialized object request on own initiative will rely on to it.Aspect oriented programming 一一Spring provides rich support, allowed by separating the application's business logic and system level service cohesiondevelopment .Application object only realize they should do 一一complete business logic・ They are not responsible for other system level concerns.Container 一一Spring contains and management application object configuration and life cycle, in this sense, it is a kind of container, you can configure each of your bean to be created 一一Based on a reconfigurable prototype (prototype), your bean can create a single instance or every time when they are needed to generate a new examples 一一and how they are interrelated・ However, Spring should not be confused with the traditional heavyweight EJB container, they are often large and unwieldy, difficult to use・ StrutsStruts on Model, View and Controller are provided with the corresponding components・ActionServlet, this is Struts core controller, responsible for intercepting the request from the user・Action, this class is typically provided by the user, the controller receives from the ActionServlet request, and according to the request tocall the model business logic method to processing the request, and the results will be returned to the JSP page display.54Part ModelBy ActionForm and JavaBean, where ActionForm used to package the user the request parameters, packaged into a ActionForm object, the object to be forwarded to the Action ActionServlet Action ActionFrom, according to which the request parameters processing a user request・JavaBean encapsulates the underlying business logic, including database access・ Part ViewThis section is implemented by JSP・Struts provides a rich library of tags, tag library can be reduced through the use of the script, a custom tag library can be achieved with Model effective interaction, and increased practical function.The Controller componentThe Controller component is composed of two parts 一一the core of the system controller, the business logic controller・System core controller, the corresponding ActionServlet.The controller is provided with the Struts framework, HttpServlet class inheritance, so it can be configured to mark Servlet .The controller is responsible for all HTTP requests, and then according to the user request to decide whether or not to transfer to business logic controller・ Business logic controller, responsible for processing a user request, itself does not have the processing power, it calls the Model to complete the dea1. The corresponding Action part・HibernateHibernate is an open source object relation mapping framework, it had a very lightweight JDBC object package, makes Java programmers can usearbitrary objects to manipulate database programming thinking .Hibernate can be applied in any use of JDBC occasions, can be in the Java client programto use, also can be in Servlet / JSP Web applications, the most revolutionary, Hibernate can be applied in theEJB J2EE schema to replace CMP, complete data persistence.The core of Hibernate interface has a total of 5, are： Session, SessionFactory, Query, Transaction and Configuration. The 5 core interface in any development will be used in. Through these interfaces, not only can the persistent object access, but also to carry out a transaction control.55中文翻译SSH为spring+ struts+ hibernate的一个集成框架，是忖前较流行的一种Web应用程序开源框架。
软件工程外文文献翻译
西安邮电学院毕业设计（论文）外文文献翻译院系：计算机学院专业：软件工程班级：软件0601学生姓名：导师姓名：职称：副教授起止时间：2010年3月8日至2010年6月11日ClassesOne of the most compelling features about Java is code reuse. But to be revolutionary, you’ve got to be able to do a lot more than copy code and change it.That’s the approach used in procedural languages like C, and it hasn’t worked very well. Like everything in Java, the solution revolves around the class. You reuse code by creating new classes, but instead of creating them from scratch, you use existing classes that someone has already built and debugged.The trick is to use the classes without soiling the existing code.➢Initializing the base classSince there are now two classes involved—the base class and the derived class—instead of just one, it can be a bit confusing to try to imagine the resulting object produced by a derived class. From the outside, it looks like the new class has the same interface as the base class and maybe some additional methods and fields. But inheritance doesn’t just copy the interface of the base class. When you create an object of the derived class, it contains within it a subobject of the base class. This subobject is the same as if you had created an object of the base class by itself. It’s just that from the outside, the subobject of the base class is wrapped within the derived-class object.Of course, it’s essential that th e base-class subobject be initialized correctly, and there’s only one way to guarantee this: perform the initialization in the constructor by calling the base-class constructor, which has all the appropriate knowledge and privileges to perform the base-class initialization. Java automatically inserts calls to the base-class constructor in the derived-class constructor.➢Guaranteeing proper cleanupJava doesn’t have the C++ concept of a destructor, a method that is automatically called when an object is destroyed. The reason is probably that in Java, the practice is simply to forget about objects rather than to destroy them, allowing the garbage collector to reclaim the memory as necessary.Often this is fine, but there are times when your class might perform some activities during its lifetime that require cleanup. As mentioned in Chapter 4, you can’t know when the garbage collector will be called, or if it will be called. So if you want something cleaned up for a class, you must explicitly write a special method to do it, and make sure that the client programmer knows that they must call this method.Note that in your cleanup method, you must also pay attention to the calling order for the base-class and member-object cleanup methods in case one subobject depends on another. In general, you should follow the same form that is imposed by a C++ compiler on its destructors: first perform all of the cleanup work specific to your class, in the reverse order of creation. (In general, this requires that base-class elements still be viable.) Then call the base-class cleanup method, as demonstrated here➢Name hidingIf a Java base class has a method name that’s overloaded several times, redefining that method name in the derived class will not hide any of the base-class versions (unlike C++). Thus overloading works regardless of whether the method was defined at this level or in a base class，it’s far more common to override methods of the same name, using exactly the same signature and return type as in the base class. It can be confusing otherwise (which is why C++ disallows it—to prevent you from making what is probably a mistake).➢Choosing composition vs. inheritanceBoth composition and inheritance allow you to place subobjects inside your new class (composition explicitly does this—with inheritance it’s implicit). You might wonder about the difference between the two, and when to choose one over the other.Composition is generally used when you want the features of an existing class inside your new class, but not its interface. That is, you embed an object so that you can use it to implement functionality in your new class, but the user of your new class sees the interface you’ve defined for the new class rather than the interface from theembedded object. For this effect, you embed private objects of existing classes inside your new class.Sometimes it makes sense to allow the class user to directly access the composition of your new class; that is, to make the member objects public. The member objects use implementation hiding themselves, so this is a safe thing to do. When the user knows you’re assembling a bunch of parts, it makes the interface easier to understand.When you inherit, you take an existing class and make a special version of it. In general, this mea ns that you’re taking a general-purpose class and specializing it for a particular need➢The final keywordJava’s final keyword has slightly different meanings depending on the context, but in general it says “This cannot be changed.” You might want to prev ent changes for two reasons: design or efficiency. Because these two reasons are quite different, it’s possible to misuse the final keywordThe following sections discuss the three places where final can be used: for data, methods, and classes.➢Final dataMany programming languages have a way to tell the compiler that a piece of data is “constant.” A constant is useful for two reasons:It can be a compile-time constant that won’t ever change.It can be a value initialized at run time that you don’t want ch anged.In the case of a compile-time constant, the compiler is allowed to “fold” the constant value into any calculations in which it’s used; that is, the calculation can be performed at compile time, eliminating some run-time overhead. In Java, these sorts of constants must be primitives and are expressed with the final keyword. A value must be given at the time of definition of such a constant.A field that is both static and final has only one piece of storage that cannot be changed.When using final with object references rather than primitives, the meaning gets a bit confusing. With a primitive, final makes the value a constant, but with an object reference, final makes the reference a constant. Once the reference is initialized to an object, it can never be changed to point to another object. However, the object itself can be modified; Java does not provide a way to make any arbitrary object a constant. (You can, however, write your class so that objects have the effect of being constant.) This restriction includes arrays, which are also objects.➢Final methodsThere are two reasons for final methods. The first is to put a “lock” on the method to prevent any inheriting class from changing its meaning. This is done for design reasons when you want to mak e sure that a method’s behavior is retained during inheritance and cannot be overridden.The second reason for final methods is efficiency. If you make a method final, you are allowing the compiler to turn any calls to that method into inline calls. When the compiler sees a final method call, it can (at its discretion) skip the normal approach of inserting code to perform the method call mechanism (push arguments on the stack, hop over to the method code and execute it, hop back and clean off the stack arguments, and deal with the return value) and instead replace the method call with a copy of the actual code in the method body. This eliminates the overhead of the method call. Of course, if a method is big, then your code begins to bloat, and you probably won’t see any performance gains from inlining, since any improvements will be dwarfed by the amount of time spent inside the method. It is implied that the Java compiler is able to detect these situations and choose wisely whether to inline a final method. However, it’s best to let the compiler and JVM handle efficiency issues and make a method final only if you want to explicitly prevent overriding➢Final classesWhen you say that an entire class is final (by preceding its definition with the final keyword), you state that you don’t want to inherit from this class or allow anyone else to do so. In other words, for some reason the design of your class is suchthat there is never a need to make any changes, or for safety or security reasons you don’t want subc lassingNote that the fields of a final class can be final or not, as you choose. The same rules apply to final for fields regardless of whet However, because it prevents inheritance, all methods in a final class are implicitly final, since there’s no way to override them. You can add the final specifier to a method in a final class, but it doesn’t add any meaning.her the class is defined as final.➢SummaryBoth inheritance and composition allow you to create a new type from existing types. Typically, however, composition reuses existing types as part of the underlying implementation of the new type, and inheritance reuses the interface. Since the derived class has the base-class interface, it can be upcast to the base, which is critical for polymorphism, as you’ll see in the next chapter.Despite the strong emphasis on inheritance in object-oriented programming, when you start a design you should generally prefer composition during the first cut and use inheritance only when it is clearly necessary. Composition tends to be more flexible. In addition, by using the added artifice of inheritance with your member type, you can change the exact type, and thus the behavior, of those member objects at run time. Therefore, you can change the behavior of the composed object at run time.When designing a system, your goal is to find or create a set of classes in which each class has a specific use and is neither too big (encompassing so much functionality that it’s unwieldy to reuse) nor annoyingly small (you can’t use it by itself or without adding functionality).类“Java引人注目的一项特性是代码的重复使用或者再生。
软件工程专业外文翻译--VB的数据库编程分析
外文原文ANALYSIS OF DATABASE PROGRAMMING IN VB VB (Visual Basic) is a visualization programming environment that Microsoft Corporation promotes based on the Basic language.It is simple and easy to study.It has formidable function so that many computer amateurs really like it.A lot of application softwares all use VB as the software development platform.When we use VB to develop the application software,how to use the database and carry on the management of the database is concerned by all exploiters.VB has provided many tools and methods for database programming.What method is used to visit the database depends on users’different demands,a simple analysis of the VB database programming is explained as followings.1.DAO TechnologyBy using Microsoft company’s Jet Database Engine (Jet database engine),DAO (Data Access Object) the technology mainly provides visit to ISAM (smooth index search method) type database,such as the realization of the visit to database like FoxPro,Access, Dbase.1.1 Use Data ControlsData controls are produced by using “Data” button in the toolbox.It has 3 basic attributes:Connect,Database Name and RecordSource.Connect attribute specifys the database type that data controls visit,the default database is the Access database.The value of the Database Name attribute is the database filename which contains the complete path.The Record Source attribute is the recordset that we visit,also can be tables or SQL sentences.If we will visit table stud of database file teacher mdb of TEMP folder under D plate,then Data controls’s Connect attribute is null,and the Database Name attribute is “D: \temp \ teacher mdb”,the value of the Record Source attribute is “stud”.This can accomplish the binding between Data controls and database records. Through the methods of Data controls like Add new,Update,Delete, Move last,we can visit the database as every request.When we browse the content in database,Data controlls is used frequently with DBGrid,it provides data inquiry in grid way.1.2 Use DAO Object StorehouseThe model of the DAO object storehouse is mainly using hierarchical structure, Dentine is the object in the topmost story,below it are two object sets,Errors and workspace, under the workspace object,is the Databases set.When the applicationprocedure quotes the DAO object storehouse,it produces only a Dentine object,and produces a default automatical working space object named workspace.When not mentioned,all database operations are all work in workspace(0),which is a default work area.But we must pay attention:The Jet engine will not starts automatically after VB has been loaded. Only when we choose References in the menu of Project can we select Microsoft DAO 3.5 Object Library to use.We create databases with the method “Create Database” in DAO,use “CreateTable” method to bulid tables,use the “Open Database ” to open the database ,use “Open recordset”method to open recordset,use Add new,Update,Delete,Move first,Edit methods to realize each kind of operations about tables.2.RDO TechnologyRDO provides a connection to related ODBC data pool.When we need to visit other databases like SQL Server,Oracle,especially to establish the customer/server application procedure,we may use the long range data controls RDC (Remote Data Control) and long range data objects RDO (Remote Data Control) to realize the visit to the database through the ODBC driver.By using ODBC to visit some database we must first install the corresponding drivers,like establish a data pool,through assigned data pool to visit corresponding database.To establish the ODBC data pool is open the window of “the control panel”, double-clicks the icon of ODBC executive program,single-click “Add” butt on to create the data pool of the opening ODBC data pool supervisor dialog box,and choose corresponding database.2.1 Use RDC ControlsSimilar to the use of DATA Controls, we use Data source name attributes to assign the data source name that controls bind,and we use SQL attributes to assign the recordset, The difference is that,we have to use the SQL sentences to assign the SQL attribute in RDC Controls . When we browse the database we may find it is used with DBGrid frequently.2.2 Use RDO Object StorehouseBefore we use RDO object,we should choose References in the menu of Project, click”Microsoft Remote Data Object 2.0”,then we can continue.The step we use RDO to visit the ODBC data pool is:(1) Set a RDO environment object.(2) Open an ODBC data pool with the method of Open connection.(3) Establish a result object with the method of Open Result set.(4) Use assigned method to operate the records of resultset.After founds the as this result collection object,is similar with the DAO object storehouse use,may through transfer method realizations and so on its Add new,Update, Delete visit to assign the data pool each kind of request.3.ADO TechnologyADO (ActiveX Data Objects) is the latest data access technology of Microsoft,It uses data accessing connection UDA (Universal Data Access),to standard all datas as a kind of data pool,through the filtration of OLEDB connection,transforms as a kind of general data format in the same way,enables the application procedure to visit this kind of datas.OLEDB is an underlying level of the data accessing connection,with it we may visit kinds of data pools,including traditional related databases,as well as electronic mail system and self-definition commercial object.3.1 Use ADO ControlsSingle-click the Components command in the menu of the Project,select “Microsoft ADO Data Control in the Components dialog box 6.0 (OLE DB)”,we may add ADO controls to the box of controls.We set the OLEDB Provider and assigned database file by setting the Connection string attribute of ADO,and we set the Record Source attribute as record source that ADO connected.Similar to DAO and RDO, with it, we are able to visit all kinds of database fastly.3.2 Use The ADO Object StorehouseSingle click the References orders in the Project menu, select “Microsoft ActiveX Data Objects 2.0 Library” in the References dialog box, you may add ADO object.Old object models, like DAO and RDO, are look like levels,a lower data object like Recordset is the sub-object of higher level objects like Environment and the Queried. But ADO is actually different, it defined a group of plane top object, the most importantADO objects are Connection, Recordset and Command.The Connection object is used to establish the connection of application procedure and the data pool.The Command object is used in defining a SQL sentence, a memory process or other commands that operates the datas.Recordset object preserves recordsets after executions.By using alternative means of the recordset object, we can modify,delete and inquire the recordset.4 ConclusionsVB provides many methods to accomplish the operation to the database, in which DAO mainly finish the visit to ISAM database, RDO provides connection to the ODBC data pool, both RDO and DAO have developed as matured technology.Before VB 6.0 ,the main technology is about database visit, however,the Active Data Objects(ADO) ,as new generation of database interface which is promoted by Microsoft, is designed to work with new data accessing level OLEDB, so that it provides general data accessing (Universal Data Access), it provides quite a lot advantages to the programmers, including easy use, the familiar contact surface, high velocity ,as well as the lower memory. As a result of above reasons, ADO will gradually replace other data accessing connections, and will becomes the fundamental mode of the VB of visit database.中文译文VB的数据库编程分析VB（Visual Basic）是微软公司推出的基于Basic语言的可视化编程环境，以其简单易学、功能强大而倍受广大电脑爱好者的青睐。
(完整)软件工程专业英语
软件工程英语文档：Documents软件工具：Software Tools工具箱：Tool Box集成工具：Integrated Tool软件工程环境：Software Engineering Environment传统：Conventional经典：Classical解空间：Solution Domain问题空间：Problem Domain清晰第一，效率第二Clarity the first，Efficiency the next。
设计先于编码Design before coding使程序的结构适合于问题的结构Make the program fit the problem开发伴随复用，开发为了复用Development with reuse, Development for reuse。
靠度量来管理:Management by Measurement软件度量学：Software Metrics软件经济学：Software Economics软件计划WHY软件分析WHAT软件实现HOW软件生存周期过程的开发标准Standard for Developing Software Life Cycle Process软件开发模型:Software Development Model编码员：Coder瀑布模型：Waterfall Model快速原型模型:Rapid Prototype Model 增量模型:Incremental Model线性思维：Linear Thinking演化模型：Evolutionary Model螺旋模型：Spiral Model对象：Object类：Class继承：Inheritance聚集:Aggregation消息：Message面向对象＝对象Object+分类Classification+继承Inheritance+消息通信Communication with Messages 构件集成模型：Component Integration Model转换模型：Transformational Model净室软件工程:Cleanroom Software Engineering净室模型：Cleanroom Model软件需求规格说明书：Software Requirement Specification ，SRS分析模型：Analysis Model便利的应用规约技术：Facilitated Application Specification Techniques ,FAST结构化语言：Structured Language判定树：Decision Tree基数：Cardinality事件轨迹：Event Trace对象－关系Object—Relationsship结构化分析:SA（Structured Analysis）由顶向下，逐步细化Top-Down Stepwise Refinement面向对象分析：Object-Oriented Analysis包含：Contains临近：Is Next To传到：Transmits to来自:Acquires from管理:Manages 控制:Controls组成:Is Composed of细化：Refinement抽象：Abstraction模块:Module策略：Strategy信息隐藏:Information Hiding数据封装：Data Encapsulation抽象数据类型：Abstract Data type模块化设计：Modular Design分解：Decomposition模块性：Modularity单模块软件：Monolithic Software模块独立性：Module Independence内聚：Cohesion偶然性内聚:Coincidental Cohesion逻辑性内聚：Logical Cohesion时间性内聚：Temporal Cohesion过程性内聚： Procedural Cohesion通信性内聚：Communicational Cohesion顺序性内聚：Sequential Cohesion功能性内聚:Functional Cohesion非直接偶合:No Direct Coupling数据偶合：Data Coupling特征偶合:Stamp Coupling控制偶合:Control Coupling外部偶合:External Coupling公共偶合：Common Coupling内容偶合： Content Coupling由底向上设计：Bottom-Up Design自顶向下设计：Top-Down Design正式复审：Formal Review非正式复审：Informal Review走查，排练：Walk-Through会审：Inspection映射:Mapping传入路径：Afferent path传出路径：Efferent path变换中心：Transform Center接受路径：Reception path动作路径:Action path事务中心:Transaction Center分支分解：Factoring of Brandches瓮形：oval-shaped一个模块的控制域：Scope of Control 一个模块的作用域：Scope of Effect 结构化程序设计：Structured Programming通心面程序:Bowl of Spaghetti流程图：Flow Diagram编码:Coding方框图：Block DiagramPDL （Pidgin）：Program Design Language伪代码：Pseudo CodeJSD:Jackson System Development对象建模技术：Object Modeling Technique基础设施:Infrastructure控制线程：Thread of Control保护者对象:Guardian Object协议：protocolUML：Unified Modeling Language OMG：Object Management Group统一方法:Unified Method关联:Association泛化:Generalization依赖：Dependency结点：Node接口：Interface包：Package注释： Note特化：Specialization元元模型：Meta—Meta Model用户模型：User Model静态图:Static Diagram动态图：Dynamic Diagram用例视图：Use Case View逻辑视图:Logical View并发视图：Concurrent View构件视图:Component View实现模型视图：Implementation Model View部署视图：Deployment View航向：Navigability重数：Multiplicity共享聚集：Shared Aggregation组合：Composition泛化：Generalization简单消息：Simple Message同步消息：Synchronous Message异步消息:Asynchronous Message事件说明：Event_Signature守卫条件:Guard_Condition动作表达式：Action_Expression 发送子句：Send_Clause时序图：Sequence Diagram协作图：Collaboration Diagram前缀:Predecessor循环子句：Iteration-Clause活动图：Activity Diagram构件图：Component Diagram配置图：Deployment Diagram建模过程指导(RUP）：Rational Unified Process可执行代码:Executalbe Codes实现：Implementation编码风格：Coding Style标准：Classical控制流的直线性：Linearity of Control Flow程序风格设计要素：先求正确后求快 Make it right before you make it faster.先求清楚后求快 Make it clear before you make it faster.求快不忘保持程序正确 Keep it right when you make it faster.保持程序简单以求快 Keep it simpleto make it faster。
软件工程外文翻译文献
软件工程外文翻译文献(文档含中英文对照即英文原文和中文翻译)Software engineeringSoftware engineering is the study of the use of engineering methods to build and maintain effective, practical and high-quality software disciplines. It involves the programming language, database, software development tools, system platform, standards, design patterns and so on.In modern society, the software used in many ways. Typical software such as email, embedded systems, human-machine interface, office packages, operating systems, compilers, databases, games. Meanwhile, almost all the various sectors of computer software applications, such as industry, agriculture, banking, aviation and government departments. These applications facilitate the economic and social development,improve people's working efficiency, while improving the quality of life. Software engineers is to create software applications of people collectively, according to which software engineers can be divided into different areas of system analysts, software designers, system architects, programmers, testers and so on. It is also often used to refer to a variety of software engineers, programmers.OriginIn view of difficulties encountered in software development, North Atlantic Treaty Organization (NATO) in 1968 organized the first Conference on Software Engineering, and will be presented at the "software engineering" to define the knowledge required for software development, and suggested that "software development the activities of similar projects should be. " Software Engineering has formally proposed since 1968, this time to accumulate a large number of research results, widely lot of technical practice, academia and industry through the joint efforts of software engineering is gradually developing into a professional discipline.Definitioncreation and use of sound engineering principles in order to obtain reliable and economically efficient software.application of systematic, follow the principle can be measured approach to development, operation and maintenance of software; that is to beapplied to software engineering.The development, management and updating software products related to theories, methods and tools.A knowledge or discipline (discipline), aims to produce good quality, punctual delivery, within budget and meet users need software.the practical application of scientific knowledge in the design, build computer programs, and the accompanying documents produced, and the subsequent operation and maintenance.Use systematic production and maintenance of software products related to technology and management expertise to enable software development and changes in the limited time and under cost.Construction team of engineers developed the knowledge of large software systems disciplines.the software analysis, design, implementation and maintenance of a systematic method.the systematic application of tools and techniques in the development of computer-based applications.Software Engineering and Computer ScienceSoftware development in the end is a science or an engineering, this is a question to be debated for a long time. In fact, both the two characteristics of software development. But this does not mean that they can be confused with each other. Many people think that softwareengineering, computer science and information science-based as in the traditional sense of the physical and chemical engineering as. In the U.S., about 40% of software engineers with a degree in computer science. Elsewhere in the world, this ratio is also similar. They will not necessarily use every day knowledge of computer science, but every day they use the software engineering knowledge.For example, Peter McBreen that software "engineering" means higher degree of rigor and proven processes, not suitable for all types of software development stage. Peter McBreen in the book "Software Craftsmanship: The New Imperative" put forward the so-called "craftsmanship" of the argument, consider that a key factor in the success of software development, is to develop the skills, not "manufacturing" software process.Software engineering and computer programmingSoftware engineering exists in a variety of applications exist in all aspects of software development. The program design typically include program design and coding of the iterative process, it is a stage of software development.Software engineering, software project seeks to provide guidance in all aspects, from feasibility analysis software until the software after completion of maintenance work. Software engineering that software development and marketing activities are closely related. Such assoftware sales, user training, hardware and software associated with installation. Software engineering methodology that should not be an independent programmer from the team and to develop, and the program of preparation can not be divorced from the software requirements, design, and customer interests.Software engineering design of industrial development is the embodiment of a computer program.Software crisisSoftware engineering, rooted in the 20th century to the rise of 60,70 and 80 years of software crisis. At that time, many of the software have been a tragic final outcome. Many of the software development time significantly beyond the planned schedule. Some projects led to the loss of property, and even some of the software led to casualties. While software developers have found it increasingly difficult for software development.OS 360 operating system is considered to be a typical case. Until now, it is still used in the IBM360 series host. This experience for decades, even extremely complex software projects do not have a set of programs included in the original design of work systems. OS 360 is the first large software project, which uses about 1,000 programmers. Fred Brooks in his subsequent masterpiece, "The Mythical Man Month" (The Mythical Man-Month) in the once admitted that in his management of theproject, he made a million dollar mistake.Property losses: software error may result in significant property damage. European Ariane rocket explosion is one of the most painful lesson.Casualties: As computer software is widely used, including hospitals and other industries closely related to life. Therefore, the software error might also result in personal injury or death.Was used extensively in software engineering is the Therac-25 case of accidents. In 1985 between June and January 1987, six known medical errors from the Therac-25 to exceed the dose leads to death or severe radiation burns.In industry, some embedded systems do not lead to the normal operation of the machine, which will push some people into the woods. MethodologyThere are many ways software engineering aspects of meaning. Including project management, analysis, design, program preparation, testing and quality control.Software design methods can be distinguished as the heavyweight and lightweight methods. Heavyweight methods produce large amounts of official documentation.Heavyweight development methodologies, including the famous ISO 9000, CMM, and the Unified Process (RUP).Lightweight development process is not an official document of the large number of requirements. Lightweight methods, including well-known Extreme Programming (XP) and agile process (Agile Processes).According to the "new methodology" in this article, heavyweight method presented is a "defensive" posture. In the application of the "heavyweight methods" software organizations, due to a software project manager with little or no involvement in program design, can not grasp the item from the details of the progress of the project which will have a "fear", constantly had to ask the programmer to write a lot of "software development documentation." The lightweight methods are presented "aggressive" attitude, which is from the XP method is particularly emphasized four criteria - "communication, simplicity, feedback and courage" to be reflected on. There are some people that the "heavyweight method" is suitable for large software team (dozens or more) use, and "lightweight methods" for small software team (a few people, a dozen people) to use. Of course, on the heavyweight and lightweight method of approach has many advantages and disadvantages of debate, and various methods are constantly evolving.Some methodologists think that people should be strictly followed in the development and implementation of these methods. But some people do not have the conditions to implement these methods. In fact, themethod by which software development depends on many factors, but subject to environmental constraints.Software development processSoftware development process, with the subsequent development of technology evolution and improvement. From the early waterfall (Waterfall) development model to the subsequent emergence of the spiral iterative (Spiral) development, which recently began the rise of agile development methodologies (Agile), they showed a different era in the development process for software industry different awareness and understanding of different types of projects for the method.Note distinction between software development process and software process improvement important difference between. Such as ISO 15504, ISO 9000, CMM, CMMI such terms are elaborated in the framework of software process improvement, they provide a series of standards and policies to guide software organizations how to improve the quality of the software development process, the ability of software organizations, and not give a specific definition of the development process.Development of software engineering"Agile Development" (Agile Development) is considered an important software engineering development. It stressed that software development should be able to possible future changes and uncertaintiesof a comprehensive response.Agile development is considered a "lightweight" approach. In the lightweight approach should be the most prestigious "Extreme Programming" (Extreme Programming, referred to as XP).Correspond with the lightweight approach is the "heavyweight method" exists. Heavyweight approach emphasizes the development process as the center, rather than people-centered. Examples of methods such as heavyweight CMM / PSP / TSP.Aspect-oriented programming (Aspect Oriented Programming, referred to as the AOP) is considered to software engineering in recent years, another important development. This aspect refers to the completion of a function of a collection of objects and functions. In this regard the contents related to generic programming (Generic Programming) and templates.软件工程软件工程是一门研究用工程化方法构建和维护有效的、实用的和高质量的软件的学科。
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软件工程外文翻译————————————————————————————————作者：————————————————————————————————日期：译文学院：电气与信息工程学院专业：软件工程学号：1245536227姓名：闫雨涛指导教师：吴惠英江苏科技大学2015 年 5 月 30 日软件工程Roger S.Pressman概念：软件项目管理开始于全体项目计划的一系列活动。
在这个项目开始之前，管理者和软件团队必须预估要做的工作量、需要多少资源、从开始到结束花费的时间。
无论何时都要进行估算，我们观察未来并且接受一定程度不确定的必然发生的事情。
引用Frederick Brooks。
人员：软件管理者，使用从客户和软件工程师处获得的信息以及从过去的项目手机的软件度量数据。
为什么重要：你会在不知道你将要花多少钱的情况下建造房子吗？当然不会，而且因为大多数情况下基于计算机系统的产品的成本大大超出建造一栋大房子，因此，在你开始创建软件前开发一个估算似乎是合理的。
步骤：估算从产品的范围的描述开始。
在范围被”界定”前，不可能得出一个有意义的估算。
然后问题被分解为一组较小的问题，而且这些问题的每一个均通过使用历史数据和经验作为指南进行估算。
明智的做法是使用至少两种不同的方法（作为交叉检查）来产生你的估算。
问题复杂度和风险需在最终的估算给出前被考虑。
产品：一个简单的表，描述将完成的任务，将实现的功能以及各自涉及的版本，工作量和时间，同时也生成一个所需项目资源的列表。
保障措施：这是很困难的。
因为在项目已经完成前，你将不可能真正知道。
然而，如果你有经验且遵循系统化的方法，用可靠的历史数据生成估算，用至少两种不同的方法创建估算数据点并考虑复杂度和风险因素，那么你可以确信你已经得出了你的最好估算。
软件项目管理过程从一组活动开始，它们被称为项目计划。
在项目可以开始前，管理者和软件小组必须估算将要完成的工作，将需要的资源以及从开始到完成所需要的时间。
无论何时进行估算，我们都是预测未来，并会接受某种程度的不确定性。
引用FrederuckBrooks[BRO75]的话：我们的估算技术发展缓慢，更为严重的是，它们隐含了一个不正确的假设，即”一切都会好的”......因为我们对自己的估算没有把握，软件管理者常常缺少让人们得到一个好产品的信心。
虽然估算是一门科学，更是一门艺术，这个重要的活动不能以随意的方式来进行。
对时时间以及工作量进行评估又用的技术确实存在。
过程和项目度量可以定量估算的生成提供历史的视角和强有力的输入，过去的（所有参与人员的）经验可以非测量的辅助估算的开发和评审。
因为估算是所有其他项目计划活动的基础，而项目计划又提供了通往成功的软件工程的道路图，所以，没有他我们就会塔错车。
5.1对估算的观察一位总经理曾经被问到：在选择一个项目管理者时，什么特质是最重要的？他的回答是：”具有在错误真正发生之前就能知道的能力”。
我们还可以加上：”在未来还是一团迷雾的时候就有勇气进行估算”。
估算一个软件开发工作的资源，成本及进度需要经验，得到以前的有用信息进行估算。
估算具有与生俱来的风险，而正是这种风险导致了不确定性。
项目复杂性对计划中固有的不确定性具有重大影响。
不过，复杂性是一个相对的测量，受到对以前工作的熟悉程度的影响。
一个复杂的电子商务应用的第一次开发者可能认为他是非常复杂的，然而一个正在开发其10个电子商务Web站点的软件小组会认为这样的工作是非常普通的。
一系列定量的软件复杂度测量已经被提出[ZUS97]，这样的测量被应用于设计或代码级，并因此而难于在软件计划中被使用（在设计和代码存在前）。
不过，关于复杂性的其他一些更为主观的评估（如第4章描述的功能点复杂度调整因子）可以在早期的计划过程中建立。
项目规模是另一个影响估算准确性和效力的因素，随着规模的增长，软件中各个元素之间的相互依赖性也迅速增加。
估算中采用的一个重要方法，问题分解，也因为分解出来的元素仍然很大而变得更为困难，解释Murphy定律:”所有可能出错的地方都会出错”，如果有更多的事情可能更改，那就更多的事情将会失败。
结构不确定性的程度也会对估算的风险产生影响。
在这里，结构是指需求能被固定的程度，功能能被分解的容易程度以及必须要处理的信息的层次性。
历史信息的可用程度对估算的风险有较强的的影响，通过回顾过去，我们能够效仿好的地方，且避免以前遇到的困难，总体风险也会降低。
风险是由资源、成本及进度建立的定量估算去测量的，如果对项目范围理解很差或项目需求不断变化，不确定性及风险就会很高。
软件计划者应该要求功能。
性能以及接口定义（包含在系统规范中）的完全性。
计划者，尤其是客户，应该认识到软件需求的变化意味着成本及进度的不稳定，然而项目管理者不应该为估算所困扰。
现代软件工程方法（如演化软件过程模型）支持开发的迭代视图，在这类方法中，当用户改变需求时，有可能会重新审查估算（在知道更多信息后）并修改之。
5.2项目计划目标软件项目计划的目标是提供一个框架，使得管理者能够对资源、成本及进度进行合理的估算。
这些估算是软件项目开始是在一个限定的时间框架内所做的，并且随着项目的进展不断更新。
此外，估算应该定义”最好的情况”及”最坏的情况”，使得项目的结果能够限制在一定范围内。
项目计划的目标是，通过发现一个信息实现的。
该过程最终导致能够进行合理的估算。
在以下各节中，我们讨论了与软件项目计划相关的每一个活动。
5.3软件范围软件项目计划的第一个活动是确定软件范围。
在系统工程阶段分配给软件的功能及性能，应该加以评估来建立一个项目范围，该范围在管理级及技术级均是可理解的。
一个软件范围的陈述必须具有边界的。
软件范围描述了将被处理的数据和控制、功能、性能、约束、接口及可靠性。
在范围陈述中给出的功能被评估，并在某些情况下被进一步精华已在估算开始之前提供更多的细节。
因为成本及进度估算都是面向功能的，所以某种程度的分界常常是很有用的。
性能方面的考虑包含处理及响应时间的要求。
约束标识了外部硬件、可用内存或其他已有系统等对软件的限制。
5.3.1获取定义软件范围所需的信息在软件项目开始时，事情总是某种程度的模糊不清。
已经定义了要求并确立了基本的目标和目的，但定义软件范围所需的信息却还没有被定义。
在客户和开发者之间建立通信的桥梁并使通信过程顺利开始的最常用的技术是举行一个初步的会议或访谈。
软件工程师和客户之间的第一次回忆可能就像青年男女的第一次约会那么尴尬。
两方都不知道说什么或问什么，两方都担心它们所说的话会被误解，两方在想会有什么结果，两方都希望事情赶快完成，但同时，两方都希望能够成功。
不管怎样，通信必须要开始。
Gause和Weinberg建议分析员开始是可以问一些与项目无关的问题，也就是说，一组使你对总体情况有一个基本了解的问题，需要解决方案的人，所期望的解决方案的性质，以及对第一次见面的效果的评价等。
第一组语境无关的问题主要集中于客户。
总体目标及收益上。
例如，分析员可能会问：谁提出了关于这项工作的要求？谁将使用这个解决方案？成功的解决方案将获得什么经济利益？是否有另一种解决方案来源？下一组问题使得分析员能够对问题有一个更好的理解，使得客户能够谈出他或她对于解决方案的想法：你认为一个成功的解决方案所产生的好的效果应该具有什么特征？这个解决方案针对什么问题？你能给我显示一下该解决方案将使用的环境吗？是否有什么特殊的性能问题或约束会影响该解决方案被实现的方式？最后一组问题主要集中于回忆的效果。
Gause和Weinberg称这些为原问题，并推荐了下免得问题列表：你是回答这些问题的最合适的人吗？你的回答是否是正式的？我的提问与你想要的问题相关吗？我是否问了太多了问题呢？是否还有其他人能够提供更多的信息？是否还有其他我应该问你的问题？这些问题能够帮助打破僵局并开始建立项目范围所必需的通信活动。
但这种问答会议的形式并不是一定会成功的。
事实上，形式仅应用于第一次见面之后，应被结合了问题解决协商及规定等多种方式的会议形式所取代。
客户和软件工程师经常有一个无意识的”我们和它们”的思维定势。
不是作为一个小组工作去标志和精华需求。
而是各方面定义自己边界并通过一系列的备忘录。
正式意见书。
文档以及提问和回答会话而通信。
历史已经证明，这样的方法不能很好的工作。
误解大量存在，重要的信息被忽略，而且成功的工作关系永不能建立。
根据这些问题有很多独立研究者提出了一种收集需求的面向小组的方法，能够用于帮助建立项目的范围。
一种方法被称为便利的应用鬼月技术，该方法鼓励建立由客户及开发者共同组成的联合小组，它们在一起工作，建议解决方案，以上不同的方法都描述了初步的需求合集。
5.3.2 可行性一旦范围已经被标志出来，人们自然会问：我们能够建造软件以满足该范围要求吗？项目是可行的吗？一个太过经常的情形是：软件工程师匆匆越过的这些问题，最终陷人从一开始就注定有问题的项目泥潭中。
并非每个事情就靠想想就是可行的，对软件而言更是如此，相反软件可行性更是如此，相反软件可行性有四个固定的条件：技术，项目是技术的可行的吗？他是具有先进水平的吗？缺陷可以减少到满足应用要求的成都吗？财政是财政可行的吗？开发可以在客户或市场可以支付的成本范围内完成吗？时间项目的完成时间可以击败竞争者吗？资源组织拥有成功所需要的资源吗？对某些在已建立的领域内的项目，这些问题的回答是容易的。
你以前已完成过这样的项目在经过几个小时或有时几周的调查后，你可确信你能够再次完成这样的项目。
在你的能力范围之外的项目却不会如此容易，一个小组可能不得不花费几个月去发现什么是一个新应用的中心的。
难于实现的需求，这些需求中的某些会带来使项目不可行的风险吗？这些风险刻意被克制吗？可行性小组应该研究高风险需求的体系结构和设计，以便可以回答这些问题。
在某些情形当小组得到否定的回答时，可能需要就减少需求进行谈判。
同时，卡通人员在用手指紧紧地敲打它们的大桌子上，经常的情况是它们气派的挥舞它们手中的粗雪茄，透过烟雾不耐烦的叫喊，足够了，开始进行。
很多这样开始的项目在几年后作为失败案例而出现在报纸上。
Putnam和Myers正确的指出仅仅范围定义是远远不够的，一旦范围被理解后，软件小组和其他人员必须工作已确定是否他能在上面提到的几个为内被完成。
这是估算过程中最重要的部分，虽然经常被忽略。
5.3.3 一个范围定义的例子与客户的通信使得我们可以定义被处理的数据和控制、必须被实现的功能、界定系统的性能和约束以及相关的信息。
举一个例子，考虑开发驱动一个传送带分类系统的软件。
对CLSS的范围陈述如下：传送带分类系统（CLSS）讲沿传送带方向移动的盒子进行分类，每一个盒子由一个包含零件号的条形码阅读器及一台PC所组成的分类站。