Abstract: A search engine is developed.The use case，class，state and package diagrams of UML are used to do the requirement analysis and design of the system.The state diagrams are enriched by means of the OCL expressions.This system is programmed in C# and ASP.NET，with SQL Server for storing information，and is run in the Microsoft .NET environment.Following the object-oriented methodology，such as refinement and modularization，in building the UML/OCL models and constructing the program，the system is hierarchically divided into modules of particular functions.The system consists of a collector，an indexer and a searcher.They are respectively responsible for information gathering，information analysis and index constructing，and user interface.The paper reports on the ideas and process of the system analysis，design and implementation.

摘要： 介绍一个搜索引擎系统的开发。运用UML用例图做系统的需求分析，运用UML类图、状态图、包图进行系统设计。以OCL表达式丰富状态图。使用C#语言和ASP.NET编程，SQL Server存储信息，系统运行在微软.NET环境上。遵循面向对象方法，如逐步求精和模块化，建立UML/OCL模型、组织程序，将系统逐层分解成具有特定功能的模块。系统由收集器、索引器、检索器三大部分组成，分别负责数据收集、数据分析和索引构建、用户检索接口。论文报告系统分析、设计和实现的思想和过程。