问题 问答题

阅读下列说明,回答问题。

[说明]

某公司拟开发一多用户电子邮件客户端系统,部分功能的初步需求分析结果如下。

(1)邮件客户端系统支持多个用户,用户信息主要包括用户名和用户密码,且系统中的用户名不可重复。

(2)邮件账号信息包括邮件地址及其相应的密码,一个用户可以拥有多个邮件地址(如user1@123.com)。

(3)一个用户可拥有一个地址簿,地址簿信息包括联系人编号、姓名、电话、单位地址、邮件地址1、邮件地址2、邮件地址3等信息。地址簿中一个联系人只能属于一个用户,且联系人编号唯一标识一个联系人。

(4) 一个邮件账号可以含有多封邮件,一封邮件可以含有多个附件。邮件主要包括邮件号、发件人地址、收件人地址、邮件状态、邮件主题、邮件内容、发送时间、接收时间。其中,邮件号在整个系统内唯一标识一封邮件,邮件状态有已接收、待发送、已发送和已删除4种,分别表示邮件是属于收件箱、发件箱、已发送箱和废件箱。一封邮件可以发送给多个用户。附件信息主要包括附件号、附件文件名、附件大小。一个附件只属于一封邮件,附件号仅在一封邮件内唯一。

该邮件客户端系统的主要关系模式如下,请填补(a)~(c)的空缺部分。

用户(用户名,用户密码)

地址簿((a),联系人编号,姓名,电话,单位地址,邮件地址1,邮件地址2,邮件地址3)

邮件账户(邮件地址,邮件密码,用户名)

邮件((b),收件人地址,邮件状态,邮件主题,邮件内容,发送时间,接收时间)

附件((c),附件号,附件文件名,附件大小)

答案

参考答案:

用户名,邮件号,邮件号

单项选择题
问答题

A hundred years ago it was assumed and scientifically" proved" by economists that the laws of society made it necessary to have a vast army of poor and jobless people in order to keep the economy going. (46) Today, hardly anybody would dare to voice this principle. It is generally accepted that nobody should be excluded from the wealth of the nation, either by the laws of nature or by those of society. The opinions, which were current a hundred years ago, that the poor owed their conditions to their ignorance, lack of responsibility, are outdated. In all Western industrialized countries, a system of insurance has been introduced which guarantees everyone a minimum of subsistence (生活维持费) in case of unemployment, sickness and old age. I would go one step further and argue that, even if these conditions are not present, everyone has the right to receive the means to subsist(维持生活), in other words, he can claim this subsistence minimum without having to have any" reason". (47) I would suggest, however, that it should be limited to a definite period of time. let’s say two years, so as to avoid the encouraging of an abnormal attitude which refuses any kind of social obligation.

This may sound like a fantastic proposal, but so, I think our insurance system would have sounded to people a hundred years ago. The main objection to such a scheme would be that if each person were entitled to receive minimum support, people would not work. (48) This assumption rests on the fallacy of the inherent laziness in human nature ; actually, aside from abnormally lazy people, there would be very few who would not want to earn more than the minimum, and who would prefer to do nothing rather than work.

(49)However, the suspicions against a system of guaranteed subsistence minimum are not groundless from the standpoint of those who want to use ownership of capital for the purpose of forcing others to accept the work conditions they offer. If nobody were forced to accept work in order not to starve, work would have to be sufficiently interesting and attractive to induce one to accept it. (50) Freedom of contract is possible only if both parties are free to accept and reject it ; in the present capitalist system this is not the case.

But such a system would not only be the beginning of real freedom of contract between employers and employees; its principal advantage would be the improvement of freedom in interpersonal relationships in every sphere of daily life.

(46) Today, hardly anybody would dare to voice this principle. It is generally accepted that nobody should be excluded from the wealth of the nation, either by the laws of nature or by those of society.