chapter01_2

assignment-2 Questions of module01Read the chapter01-chapter03 of textbook, answer the following questions:1.Discuss the meaning of each of the following terms:(a) dataData is the physical symbols that represent different kinds of information.(b) databaseA Shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization.(c) database management systemDatabase management system is a software system that enables users to define, create, and maintain the database and that provides controlled access to this database.(d) data independenceThis is essentially the separation of underlying file structures from the programs that operate on them,also called program-data independence.(e) views.A virtual table that does not necessarily exist in the database but is generated by the DBMS from the underlying base tables whenever it’s accessed.2.What is the difference between conceptual and logical data models? Giveexamples of each.Conceptual data models: Used to describe data independently of any system；Purpose is to represent the concepts of the real world；Used in early stages of database design；Example: entity-relationship (E-R) modelLogical data models:Used in DBMSs for the organization of data at a level that abstracts from physical structuresExample:the relational data modelthe network data modelthe hierarchical data model3.Define the terms relation, schema, instance and attribute. Give examples.Relations is a table with columns and rows.Example:Courses（course,tutor,room）The schema represents the structure of the data .Example:Schema of Courses is (Course, Tutor, Room)The instance represents the actual values.Example:The instances of Courses are the contents of the tables4.What is the purpose of the three levels (i.e. physical, logical and external) fora DBMS?Separate each user’s view of the database from the way the database is physically represented.5.What is the difference between the DML and DDL parts of SQL? What partwould you use to (i) create a table to hold information about employees, (ii) add information about a new employee to the table, and (iii) find out thesalary of one of the employees?The database administrator often interacts with the database via a “Data Definition Language” or DDL.Database users interact with the database via a “Data Manipulation Language” or DML.DDL DML DML6.Describe the five components of the DBMS environment and discuss howthey relate to each other.Hardware:The computer system(s) that the DBMS and the application programs run on. This can range from a single PC, to a single mainframe(主机), to anetwork of computers.Software:The DBMS software and the application programs, together with theoperating system, including network software if the DBMS is being used over a network.Data:Used by the organization.The data acts as a bridge between the hardware and software components and the human components.Procedures:Instructions and rules（操作说明和规则）that should be applied to the design and use of the database and DBMS.People:Includes DBMS designers and implementers(实现者), database designers, database administrators ( DBAs), application programmers, and end-users.7.What is logical data independence?Logical data independence refers to the immunity of the external schema to the changes in the conceptual schema.8.what is physical data independence?Physical data independence refers to the immunity of the conceptual schema to the changes in the internal schema.。

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Let a, b, and c represent elements of the set of integers. Under the operation of addition, the following properties are true:
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The Integers
Exercises Writing About Mathematics
1. Tina is three years old and knows how to count. Explain how you would show Tina that 3 1 2 5 5.
2. Greg said that ͉a 2 b͉ 5 ͉b 2 a͉. Do you agree with Greg? Explain why or why not.
DEFINITION
The opposite or additive inverse of a is 2a, the number such that a 1 (2a) 5 0.
The set of integers is the union of the set of whole numbers and their opposites. The set of non-zero whole numbers is the positive integers and the opposites of the positive integers are the negative integers.
Rosie Barbi is playing in an amateur tournament. Her standing is recorded as 2 below par (22) after sixteen holes. She shoots 2 below par on the seventeenth hole and 1 above par on the eighteenth. What is Rosie’s standing after eighteen holes? Nancy Taylor, who is her closest opponent, has a standing of 1 below par (21) after sixteen holes, shoots 1 below par on the seventeenth hole and 1 below par on the eighteenth.What is Nancy’s standing after eighteen holes?

[GROWING PAINS]02 SpringsteenThis is it, my Springsteen tickets.是我的，肯定是斯普林斯汀的演唱会门票When do they outgrow skateboards? 他们什么时候才会不再喜欢溜冰板？[outgrow: 过大而不适于, 长大成熟而不再]When you buy them a Camaro(美系车科迈罗). 等你给他们买了车之后Yeah, okay. Bye. 对，好的。

拜。

Gonna see Springsteen, huh? 要去听斯普林斯汀的演唱会，嗯？Yep. Tomorrow night. It's gonna be awesome(极好的).对，明天晚上，肯定很精彩Ladies and gentlemen... the Boss. 女士们先生们…演出开始Wait, wait. I thought the Springsteen concert was sold-out(卖光的,满员的).我还以为演唱会的票一早卖光了呢Sold-out? Carol, to a man with connection s, nothing is ever sold-out.卖光了？对一个有门路的男人来说，没有东西买不到。

[connection: 关系] That just happened to be Seth Jameson, nephew of the man whose brother-in-law owns a hot-dog concession at the Coliseum(大体育场,大剧场).[happen to: 碰巧；nephew: 侄子; concession: 特许(权)]刚才打电话来的是塞斯.詹姆森，他叔叔的小舅子在体育馆里面有个卖热狗的摊位-Wow. -So did you get tickets? -哇哦。

《呼啸山庄》逐章内容概述 (1)章节一: 1801年12月20日故事以第一章开始，时间设定在1801年12月20日。

读者通过主人公、叙述者之一的Lockwood的视角了解到了故事的背景和环境。

Lockwood是一个伦敦律师，在寻找乡村居所的过程中来到了呼啸山庄。

他的房东是一个叫做Heathcliff的男人，一个神秘而古怪的人物。

在这一章中，Lockwood描述了Heathcliff的外貌和他对他的印象，还遇到了一个叫做Cathy的女孩，她是Heathcliff的养女。

章节二: 1801年12月22日第二章发生在1801年12月22日。

Lockwood因为天气变得危险而被迫留宿在呼啸山庄。

在这个晚上，他偶然发现了一个房间，房间中有一些奇怪的东西，以及一个刻有"Catherine Earnshaw, Catherine Heathcliff, Catherine Linton"的刻字。

Lockwood还做了一个梦，梦到了一个叫做Catherine的女孩。

第二章结束时，Lockwood决定第二天离开呼啸山庄。

章节三: 1801年12月24日第三章发生在1801年12月24日。

Lockwood回到了呼啸山庄，他希望找到Heathcliff以解释他在梦中看到的事情。

在山庄里，他遇到了一位叫做Nelly Dean的女仆，她是Cathy的管家。

Nelly Dean开始向Lockwood讲述了关于Heathcliff、Cathy和其他人的故事。

这一章中，Nelly Dean回忆起了Heathcliff和Cathy的童年时光，以及他们之间的亲密关系。

章节四: 1771年第四章讲述了1771年的故事。

Nelly Dean继续向Lockwood回忆起过去的事情。

她描述了Cathy的父亲Mr. Earnshaw带回了一个被他命名为Heathcliff的孤儿，并将他带入了呼啸山庄。

Cathy和Heathcliff逐渐成为了好朋友，但是他们的关系却引起了Cathy的兄弟Hindley的嫉妒。