问题 问答题 简答题

设计E-R图应遵循哪些主要原则?

答案

参考答案:

(1)首先针对特定用户的应用,确定实体、属性和实体间的联系,作出反映该用户视图的局部E-R图。

(2)综合各个用户的局部E-R图,产生反映数据库整体概念的总体E-R图。在综合时,删掉局部E-R图中的同名实体,以便消除冗余,保持数据的一致性。

(3)在综合局部E-R图时,还要注意消除那些冗余的联系,冗余信息会影响数据的完整性,使维护工作复杂化,但有时也要折中考虑,有时必要的冗余会提高数据处理效率。

(4)综合时也可以在总体E-R图中增加新的联系。

经过综合后的E-R图应尽量能真实地模拟现实世界,也容易被用户理解。

阅读理解

Sagrada Familia ( 2,056,448 visits/year)

Opening hours: 09:00—18:00 (October—March); 09:00—20:00 (April—September)

Admission: $ 11, or $ 10 with the Barcelona Card.

Disabled Access: Yes.

The temple have been under construction since 1882 and they’ve still got another 30 to 80 years to go before it will be finished. The project’s vast scale and its special design have made it one of Barcelona’s top tourist attractions for many years.

La Pedrera (1,133,220 visits/year)

Opening hours: November—February: 09:00—18:30; March—October: 09:00—20:00

Admission: $ 9.50. Save 20% with the Barcelona Card.

Disabled Access: No.

This building used to be called Casa Mila but nowadays it’s more commonly known as La Pedrera. It is a unique modernist building in Barcelona and was made of bricks and had colorful tiles (瓦). It was built between 1906 and 1912 by famous Catalan architect Antoni Gaudi (1852—1926) and in 1984 it was declared a UNESCO World Heritage site with other Gaudi buildings in Barcelona. Visitors to La Pedrera can see the amazing 800 square meters attic with 270 brick arches that give you a feeling that you are walking inside the skeleton (骨架) of a whale. The roof is equally impressive and is preserved exactly the way that it was built in 1912 with six staircases and seven chimneys each made in a unique style.

Barcelona FC Museum (1,032,763 visits/year) 

Opening hours: 6th April—4th October: (Monday to Saturday) 10:00—20:00; the rest of the year: 10:00—18:30

Admission: $ 8.50 for entry to the museum and $ 17 for a guided tour.

Disabled Access: Yes.

When you buy your ticket you have two options. You can buy a ticket for the museum to see the football stadium or you can buy a dual (双的) ticket for $ 15 where you get to see the museum and the scenes at the club.

Miro Museum (518,869 visits/year)

Opening hours: Check the web site for details as they vary depending on the time of the year.

Admission: $ 8. Save 20% with the Barcelona Card.

Disabled Access: Yes.

This museum has a wide range of Miro’s work dating back as far as 1914. This artwork collection not only includes his paintings but also a good selection of sculptures (雕塑).

L’Aquarium de Barcelona (1,375,271 visits/year)

Opening hours: 09:00—19:00 (October—March); 09:00—20:00 (April—September)

Admission: $ 7. Save 10 % on the entrance fee to the aquarium with the Barcelona Card.

Barcelona Aquarium is a popular Barcelona attraction to take the kids and young ones. I have to admit I love the aquarium.

Picasso Museum (887,958 visits/year)

Opening hours: Check the website for details as they vary depending on the time of the year.

Admission: $ 9 for main exhibition—extra for special showings. Save 50% with the Barcelona Card.

Disabled Access: Yes. The museum has arranged Picasso’s paintings in chronological order from his early days to his final works. Arranging the paintings in this way gives you a fascinating insight into the development of Picasso thinking over time and shows how he developed the distinctive designs that he is famous for today. Very popular art gallery.

小题1:Which of the following attractions is the most popular with people?

A.Sagrada Familia

B.La Pedrera

C.Barcelona FC Museum

D.Picasso Museum小题2:What do we know about the tourist attractions mentioned in the above passage?

A.Sagrada Familia is the largest building in Barcelona.

B.La Pedrera is well-known for its colorful material.

C.Barcelona FC Museum may attract football fans.

D.Miro Museum was built in 1914.小题3:If you visit the stadium and the club with a tour guide in Barcelona FC Museum, you should pay ________.

A.$ 25.5

B.$ 32

C.$ 42.5

D.$ 34小题4:What do the attractions have in common?

A.They are all famous for their architectural style.

B.They are available for the disabled people.

C.Their opening hours are changeable in different seasons.

D.Tourists can have a discount of 20% with the Barcelona Card.

单项选择题