一个软件产品开发完成投入使用后，常常由于各种原因需要对它做适当的变更。在软件的使用过程中，软件原来的(48)可能不再适应用户的要求，需要进行变更；软件的工作环境也可能发生变化，最常见的是配合软件工作的(49)有变动；还有一种情况是在软件使用过程中发现错误，需要进行修正。通常把软件交付使用后做的变更称为(50)。软件投入使用后的另一项工作是(51)，针对这类软件实施的软件工程活动，主要是对其重新实现，使其具有更好的(52)，包括软件重构、重写文档等。(51)和新的软件开发工作的主要差别在于(53)。

(65)

(63)

(64)

Originally, the World-Wide Web was designed as information medium for (71) research teams. A deliberately simple implementation model was chosen to make it as simple as possible for authors to (72) documents to the web, and to (73) these in the sense of updating content. This implementation model is centered around the notion of resources, usually file-base D. For the (74) intended use of the web, resources presented a useful abstraction, as they related to relatively self-contained chunks of information such as research publications and (75) pages. Such chunks of information typically could be set up and maintained independently of other resources, so that resources were the appropriate abstraction for composition and modification.

(62)

(60)

(58)

(59)

(57)

UML-based tools are often used for J2EE/.NET application analysis and design, both because UML's object orientation is ideal for the J2EE/.NET implementation(66)and because of the expanding scope and complexity of today's enterprise endeavors.(67)the approaches diverge at the coding/implementation phase, a common set of analysis and design techniques applies to both J2EE and.NET.

 The use of a virtual, machine(VM)architecture is also common to J2EE and .NET. Application development tools(68)intermediate-level code instead of platform-specific binary code, which means the VM interprets that code in real time or performs Just-In-Time(JIT)compilation; the Microsoft VM always runs JIT-compiled code. This VM-based model results in(69)-independent applications and is conducive to the late-binding technique that's(70)to the OO approach.