计算机相关外文翻译-----一种新的网络应用程序开发框架——mvc.doc

摘要
MVC(Model/View/Controller)的设计模式出现在在Smalltalk-80,并在软件的设计中广泛应用。本文介绍一种基于MVC框架的的新网络应用程序。这种框架把实施逻辑与表现形式独立开来。它也提高了系统的可维护性,可扩展性以及使用模块数据库备案、模板数据库,通讯对象和缓冲队列的性能。
关键词:MVC、设计模式、网络应用程序

1.简介
网络应用系统是一个基于B(rowser)/ S(erver)模型应用系统。它利用多种动态网页开发技术。目前,软件设计的主题之一是网络应用开发模式和工具的。它们直接影响系统的几个关键因素,比如可维护性、可扩展性、稳定性和安全性。本文中，基于MVC[1]的网络应用程序的设计模式是为解决这两类因素——扩展性和可维护性这些不易处理的问题。把MVC设计模式引入网络应用程序开发，执行逻辑可以独立于系统的表现形式。
MVC由三种对象组成。1)模型:是应用对象，2)视图:是它的屏幕的显示,3)控制器:
定义用户界面并对输入的信息做出响应。在出现MVC之前,用户界面的设计倾向于把这些东西做在一起。然而,MVC独立了它们，增加系统的灵活性和可重用性。MVC把视图和模型独立开来,在它们之间建立了“subscribe/notify”协议。一个视图必须确保其正确反映模型的状态。每当模型的数据发生改变,视图会得到相应的通知。作为回应,每个视图都会有更新自身的机会。这个方法可以让你附上一个模型的多个视图以便提供不同的报告。你也可以不改变原模型同时创建新的视图。

2.背景和存在的问题
虽然MVC的设计模式已经在smalltalk-80中提出了,并广泛应用于软件设计,介绍它到网页应用程序开发却仍很困难的。主要由于以下两个因素:1)首先,很难独立
来自HTML的编程语言。早期的CGI程序使用字符串输出创造了HTML内容。默认的,将HTML文本分成几份,然后把他们嵌入到CGI程序中。脚本语言出现后,变成了脚本语言编写的程序嵌入到HTML文本中。然而,这两种方法有一个共同的不足,使他们不能完


Abstract
The MVC (Model/View/Controller) design pattern was developed in Smalltalk-80 and widely used in software design. This paper introduces a novel Web application frame based on MVC. This frame separates the transaction logic from the presentation format. It also improves the system maintainability, scalability and performance by using the module database, template database, messaging object and buffer queue.
Key words: MVC, Design Pattern, Web Application

1. Introduction
Web application system is a transaction system based on B (rowser)/S(erver) model. It exploits many kinds of dynamic Web developing technologies. At present, Web application developing patterns and tools are one of the topics of the software design. They directly influence several key factors such as maintainability, scalability, stability and the security. In this paper, the purpose of MVC[1]-based Web application design pattern is to resolve the two factors – maintainability and scalability, which are the stubborn problems in the Web application development. By introducing the MVC design pattern into the Web application development, the implementation of system transaction logic can be separated from the system presentation.
MVC consists of three kinds of objects. 1) the Model: is the application object, 2) the View: is its screen presentation, 3) the Controller: defines the way the user interface reacts to user input. Before MVC, user interface designs tended to lump these objects together. However, MVC decouples them to increase the flexibility and reuse. MVC decouples views and models by establishing a “subscribe/notify” protocol between them. A view must ensure that its appearance reflects the state of the model correctly. Whenever the model’s data changes, the model notifies views that depend on it. In response, each view gets an opportunity to update itself. This approach lets you attach multiple views to a model to provide different presentations. You can also create new views for a model without rewriting it.

2. Background and Problems
Even though the MVC design pattern was already put forward in smalltalk-80 and widely used in software design, it is difficult to introduce it into the Web application development. It was mainly due to the following two factors: 1) First, it was difficult to separate the programming language from HTML. Early CGI programs created the HTML content by using character string output. In nature, it divided the HTML content into several portions, and then inserted them into the CGI programs. After the appearance of Script languages, the way changed to insert the programs written by script languages into HTML content. However, these two ways had a common deficiency that they could not separate the programs from the HTML content absolutely. Therefore, it is very difficult to implement the MVC detached three-layer pattern based on these two ways. 2) Second, functions of the script languages are less weak. They lack some necessary technologies to support the MVC design pattern, such as message mechanism and event response