1、（ 2009 届毕业设计） 外文翻译原文及译文 学 院（部）： 计算机与通信学院 专 业： 计算机科学与技术 学 生 姓 名： 班 级： 指导教师姓名： 职称 副教授 2009 年 4 月 本科毕业设计（外文翻译原文 及译文） 1 The Semantic Web: An Overview Data Independence An important point about database systems is that the database should exist independently of any of the specific applications. Tradition
2、al data processing applications are data dependent. COBOL programs contain file descriptions and record descriptions that carefully describe the format and characteristics of the data. Users should be able to change the structure of the database without affecting the applications that use it. For ex
3、ample, suppose that the requirements of your applications change. A simple example would be expanding ZIP codes from five digits to nine digits. On a traditional approach using COBOL programs each individual COBOL application program that used that particular field would have to be changed, recompil
4、ed, and retested. The programs would be unable to recognize or access a file that had been changed and contained a new data description； this, in turn, might cause disruption in processing unless the change were carefully planned. Most database programs provide the ability to change the database str
5、ucture by simply changing the ZIP code field and the data-entry form. In this case, data independence allows for minimal disruption of current and existing applications. Users can continue to work and can even ignore the nine-digit code if they choose. Eventually, the file will be converted to the n
6、ew nine-digit ZIP code, but the ease with which the changeover takes place emphasizes the importance of data independence. Data Integrity Data integrity refers to the accuracy, correctness, or validity of the data in the database. In a database system, data integrity means safeguarding the data agai
7、nst invalid alteration or destruction arise. The first has to do with many users accessing the database concurrently. For example, if thousands of travel agents and airline reservation clerks are accessing the database concurrently. For example, if thousands of travel agents and airline reservation
8、clerks are accessing the same database at once, and two agents book the same seat on the same flight, the first agents booking will be lost. In such case the technique of locking the record or field provides the means for preventing one user from accessing a record while another user is updating the
9、 same record. 本科毕业设计（外文翻译原文 及译文） 2 The second complication relates to hardwires, software, or human error during the course of processing and involves database transactions treated as a single . For example, an agent booking an airline reservation involves several database updates (i.e., adding the
10、passengers name and address and updating the seats-available field), which comprise a single transaction. The database transaction is not considered to be completed until all updates have been completed； otherwise, none of the updates will be allowed to take place. Data Security Data security refers
11、 to the protection of a database against unauthorized or illegal access or modification. For example, a high-level password might allow a user to read from, write to, and modify the database structure, whereas a low-level password history of the modifications to a database-can be used to identify wh
12、ere and when a database was tampered with and it can also be used to restore the file to its original condition. Choosing between Oracle and SQL Server I have to decide between using the Oracle database and WebDB vs. Microsoft SQL Server with Visual Studio. This choice will guide our future Web proj
13、ects. What are the strong points of each of these combinations and what are the negatives? Lori: Making your decision will depend on what you already have. For instance, if you want to implement a Web-based database application and you are a Windows-only shop, SQL Server and the Visual Studio packag
14、e would be fine. But the Oracle solution would be better with mixed platforms. There are other things to consider, such as what extras you get and what skills are required. WebDB is a content management and development tool that can be used by content creators, database administrators, and developer
15、s without any programming experience. WebDB is a browser-based tool that helps ease content creation and provides monitoring and maintenance tools. This is a good solution for organizations already using Oracle. Oracle also scales better than SQL Server, but you will need to have a competent Oracle
16、administrator on hand. The SQL Sever/Visual Studio approach is more difficult to use and requires an experienced object-oriented programmer or some extensive training. However, you do get a fistful of development tools with Visual Studio: Visual Basic, Visual C+, and Visual InterDev for only $1,619. Plus, you will have to add the cost of the SQL Server, which will run you $1,999 for 10 clients or $3,999 for 25 clients-a less expensive solution than
