One of the difficulties in building an SQL-like query language for the Web is the absence
A.schema
B.platform
C.module
D.relation
A.schema
B.platform
C.module
D.relation
One of the difficulties in building an SQL-like query language for the Web is the absence of a database(1)for this huge, heterogeneous repository ofinformation. However, if we are interested in HTML documents only, we can construct a virtual schema from the implicit structure ofthese files. Thus, at the highest level of(2), every such document is identified by its Uniform Resource Locator (URL), a(3)and a text. Also, Web servers provide some additional information such as the type, length, and the last modification date of a document. So, for data mining purposes, we can consider the set of all HTML documents as a relation:
Document (url, title, text,type, length, modify)
Where all the(4)are character strings. In this framework, an individual document is identified with a(5)in this relation. Ofcourse, if some optional information is missing from the HTML document, the associate fields will be left blank, but this is not uncommon in any database.
阅读理解。 |
American Youth Millions of words have been written about young people in the United States. There are reasons for this great interest in the ideas, feelings, and actions of youth. Today there are about seven million Americans in colleges and universities. Young persons under twenty- fivemake upnearly half of the American population. Many of these will soon be in charge of the nation. Naturally their ideas are important to everyone in the country, and it is necessary for older people to understand what they think and feel. College students today have strong opinions about right and wrong. They are deeply interested in making a better life for all people, especially for those who have not been given a fair chance before now. They see much that is wrong in the lives of their parents. It is hard for them to see what is right and good in the older ways. As a result, there is often trouble in American families. Your country may be meeting such problems, too. |
1. The meaning of the underlined phrase "make up" is _____. |
A. 编造 B. 构成 C. 补偿 D. 化妆 |
2. Which of the statements would the writer probably agree? |
A. It is unfortunate that so much attention is being paid to young people in the United States. B. Older people should try to understand the thoughts and feelings of youth. C. Many problems today are caused by parents who do not control their children. D. The young people of today are mainly interested in enjoying life. |
3. The last sentence says, "Your country may be meeting such problems, too." The phrase "such problems" refers most directly to _____. |
A. crime caused by the use of drugs B. the newer sexual freedom of youth C. young people's dislike of hard work D. disagreements between young people and their parents |
A、smell
B、touch
C、taste
D、sight
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