问题 单项选择题

某软件公司欲开发一个在线交易系统。为了能够精确表达用户与系统的复杂交互过程,应该采用UML的()进行交互过程建模。

A.类图

B.序列图

C.部署图

D.对象图

答案

参考答案:B

解析:

一个系统的行为可以用许多方法来说明,包括协作或者交互的方法。用例设计通常使用交互(特别是序列图)来说明系统的行为。当系统或者子系统的行为主要通过同步消息传递来说明时,序列图非常有用。由于消息序列通常没有严格的定义,因此,尤其是在事件驱动系统中,异步消息传递更容易利用状态机和协作来进行说明。

单项选择题
阅读理解

Switching telephone providers used to be the only way homeowners could save money on telephone bills. Now thanks to new technology, comsumers have another choice-making phone calls over the internet. And this can be completely free if you call another person with an internet phone set-up.

The technology is called voice over internet protocol (协议), or VoIP. In 2005, consumer demand for VoIP dramatically grew. In the US, where popularity has grown faster than here in the UK, 8.4 million are predicted to subscribe this year. For the past couple years, VoIP pioneers such as Skype have accounted for the majority of internet phone subscribers.

VoIP is attractive to consumers because it’s cheaper than traditional phone services. With the basic equipment of PC, microphone and headset, and VoIP software and broadband internet for optimum (最适宜的) voice quality, consumers can save a fortune chatting for free to other internet phone owners and save money calling regular landlines (通讯电缆). But, as the saying goes, you get what you pay for. Many of these services suffer from uncontinuous lapses (失效) in quality. While some users may tolerate echoes or a dropped call, improved quality is needed to attract more customers.

Computing has examined the benefits of using a PC as a telephone with VoIP in how easy they were to set up, how effective they were and the range of their features.

Skype(www. skype.com) came top for its bother-free approach, easy set-up and exceptional voice clarity. Sipgate (www. sipgate. co. uk), MSN(www. messenger. msn. co. uk) and Yahoo! Messenger (uk. messenger. yahoo. com) provide an audio “wizard” that improves sound levels. Google Talk (www. google. com/ talk) was less helpful and Babble. net (www. babble. net) was let down by its poor help files. Yahoo! Messenger provides some of the best features, including the option of landline calls, webcam chats, instant messaging, voice-mail and conference calls.

小题1:Which one of the following if you call others?

A.VolP,voice over internet protocol

B.Switching telephone

C.New technology

D.letters小题2:The underlined sentence in Paragraph 3 implies that ______.

A.VoIP can save money but it has some disadvantages

B.whatever you buy is related to how much you pay

C.what you pay for will belong to you forever

D.what you buy is not always high in quality小题3:Which of the following statement is true according to the passage?

A.Sipgate is less helpful.

B.Yahoo! Messenger offers some best features.

C.Skype is the best one in the new technology.

D.Google Talk provides very good audio “wizard”.