C.1.4 Identify the characteristics of the following URI URL:
C.1.4 识别以下 URI URL 的特征：

uniform resource identifier (URI) 
统一资源标识符（URI）

URL.

The power of a link in the Web is that it can point to any document (or, more generally, resource) of any kind in the universe of information. This requires a global space of identifiers. These Universal Resource Identifiers are the primary element of Web architecture. 
Web 中链接的强大之处在于，它能指向信息宇宙中任何类型的文档（或更广义的资源）。这需要一个全局标识符空间，这些通用资源标识符构成了 Web 架构的主要元素。

A Uniform Resource Identifier (URI) is a compact sequence of characters that identifies an abstract or physical resource. Basically it is a term for an identifier of a resource. It identifies a ‘thing’, but does not give any information about where to find it. 
统一资源标识符(URI)是标识抽象或物理资源的紧凑字符序列。基本上它是资源标识符的术语。它标识一个"事物"，但不提供任何关于如何定位该事物的信息。

A Uniform Resource Identifier (URI) is a compact sequence of characters that identifies an abstract or physical resource. Basically it is a term for an identifier of a resource. It identifies a ‘thing’, but does not give any information about where to find it.
统一资源标识符 (URI) 是一个用于标识抽象或物理资源的紧凑字符序列。本质上，它是资源标识符的术语。它标识一个"事物"，但不提供关于如何找到该事物的任何信息。

A URI can be further classified as a locator, a name, or both. The term “Uniform Resource Locator” (URL) refers to the subset of URIs that, in addition to identifying a resource, provide a means of locating the resource by describing its primary access mechanism (e.g., its network “location”)
URI 可进一步分类为定位符（locator）、名称（name）或两者兼具。术语"统一资源定位符"（URL）特指 URI 的子集，这类标识符不仅能够识别资源，还能通过描述其主要访问机制（例如其网络"位置"）提供定位该资源的方法。

URL Is the global address of documents and pages/resources on the world wide web
URL 是万维网上文档和页面/资源的全球地址
Difference: URI only identifies the network resource, URL helps locate that resource as well and also defines the mechanism as to how to retrieve the resource over the web
区别：URI 仅标识网络资源，URL 不仅帮助定位该资源，还定义了如何通过 web 检索该资源的机制

Note: network resources are files that can be plain Web pages, other text documents, graphics, or programs.
注意：网络资源可以是普通网页、其他文本文档、图形或程序文件。

The first part of a protocol is called a protocol identifier and indicates to the browser what protocol to use. The second part is called resource name and it specifies the ip address/domain name of where the resource is located on the world wide web.
协议的第一部分称为协议标识符(protocol identifier)，用于向浏览器指示应使用哪种协议。第二部分称为资源名称(resource name)，它指定了资源在万维网(world wide web)上所处位置的 IP 地址/域名(ip address/domain name)。

C.1.5 Describe the purpose of a URL
C.1.5 描述 URL 的用途

From above, URL is the global address of documents and pages/resources on the world wide web. The first part of a protocol is called a protocol identifier and indicates to the browser what protocol to use. The second part is called resource name and it specifies the ip address/domain name of where the resource is located on the world wide web.
如上所述，URL 是全球万维网上文档和页面/资源的统一地址。协议的第一部分称为 protocol identifier（协议标识符），用于指示浏览器使用何种协议。第二部分称为 resource name（资源名称），指定了资源在万维网上所处位置的 ip address（IP 地址）/domain name（域名）。

The purpose of URL is to tell the server which webpage to display or to search for.
URL 的用途是告诉服务器要显示哪个网页或进行搜索。

The URL contains the name of the protocol to be used to access a file resource
URL 中包含要用于访问文件资源的协议名称

A URL (Uniform Resource Locator), as the name suggests, provides a way to locate a resource on the web
URL（Uniform Resource Locator），顾名思义，提供了一种在网络上定位资源的方法

C.1.6 Describe how a domain name server functions
C.1.6 描述域名服务器如何运作

C.1.7 Identify the characteristics of: IP, TCP and FTP
C.1.7 识别以下协议的特征：IP、TCP 和 FTP

C.1.8 Outline the different components of a web page.
C.1.8 概述网页的不同组件。

C.1.9 Explain the importance of protocols and standards on the web.
C.1.9 解释协议和标准在网络上的重要性。

C.1.10 Describe the different types of web page
C.1.10 描述不同类型的网页

Client-side Environment  客户端环境

The client-side environment used to run scripts is usually a browser. The processing takes place on the end users computer. The source code is transferred from the web server to the users computer over the internet and run directly in the browser.
用于运行脚本的客户端环境通常是浏览器。处理过程发生在最终用户的计算机上。源代码通过互联网从网络服务器传输到用户的计算机，并直接在浏览器中运行。

The scripting language needs to be enabled on the client computer. Sometimes if a user is conscious of security risks they may switch the scripting facility off. When this is the case a message usually pops up to alert the user when script is attempting to run.
必须在客户端计算机上启用脚本语言。有时，如果用户意识到安全风险，他们可能会关闭脚本功能。当出现这种情况时，通常会弹出一条消息，在脚本试图运行时提醒用户。

Server-side Environment  服务器端环境

The server-side environment that runs a scripting language is a web server. A user's request is fulfilled by running a script directly on the web server to generate dynamic HTML pages. This HTML is then sent to the client browser. It is usually used to provide interactive web sites that interface to databases or other data stores on the server.
运行脚本语言的服务器端环境是 web 服务器。用户的请求通过直接在 web 服务器上运行脚本来生成动态 HTML 页面，从而得到满足。该 HTML 随后被发送至客户端浏览器。该技术通常用于提供与服务器端数据库或其他数据存储进行交互的交互式网站。

This is different from client-side scripting where scripts are run by the viewing web browser, usually in JavaScript. The primary advantage to server-side scripting is the ability to highly customize the response based on the user's requirements, access rights, or queries into data stores.
这与客户端脚本不同，客户端脚本通常由查看网页的浏览器（使用 JavaScript）运行。服务器端脚本的主要优势在于能够根据用户需求、访问权限或对数据存储的查询，高度定制响应内容。

HTML are markup languages, basically they are set of tags like <html>, <body>, which is used to present a website using css, and javascript as a whole. All these, happen in the clients system or the user you will be browsing the website.
HTML 是标记语言，本质上是一组标签，如、，用于结合 css 和 javascript 共同呈现网站。所有这些都发生在客户端系统或用户浏览网站时。

Now, Connecting to a database, happens on whole another level. It happens on server, which is where the website is hosted.
现在，连接到数据库（database）发生在完全不同的层面。这发生在服务器（server）上，也就是网站托管的地方。

So, in order to connect to the database and perform various data related actions, you have to use server-side scripts, like php, jsp, asp.net etc.
因此，为了连接到数据库并执行各种与数据相关的操作，您必须使用服务器端脚本，如 php、jsp、asp.net 等。

Now, lets see a snippet of connection using MYSQL Extension of PHP
现在，让我们来看一段使用 PHP 的 MYSQL 扩展进行连接的代码片段

$db= mysqli_connect('hostname','username','password','databasename');

This single line code, is enough to get you started, you can mix such code, combined with HTML tags to create a HTML page, which is show data based pages. For example:
这行单行代码足以让你入门，你可以将此类代码与 HTML 标签结合使用，创建出能够展示数据驱动型页面的 HTML 页面。例如：

<?php

$db= mysqli_connect('hostname','username','password','databasename');

?>  《选项 C 网络科学 - 计算机科学 初高中课程》

<html>   ...

<body>

<?php

$query="SELECT * FROM `mytable`;"
$query="SELECT * FROM `mytable`;";;

$result= mysqli_query($db,$query);
$result = mysqli_query($db, $query);

while($row= mysqli_fetch_assoc($result)){
while($row = mysqli_fetch_assoc($result)){

// Display your datas on the page
// 在页面上显示您的数据

}

?>

</body>

</html>

CGI is a method used to exchange data between the server and the web browser. CGI is a set of standards where a program or script can send data back to the web server where it can be processed.
CGI 是一种用于在服务器和网络浏览器之间交换数据的方法。CGI 是一套标准，允许程序或脚本将数据发送回网络服务器进行处理。

Common Gateway Interface (CGI) offers a standard protocol for web servers to execute programs that execute like Console applications (also called Command-line interface programs) running on a server that generates web pages dynamically. Such programs are known as CGI scripts or simply as CGIs. The specifics of how the script is executed by the server are determined by the server. In the common case, a CGI script executes at the time a request is made and generates HTML.
通用网关接口（Common Gateway Interface，CGI）为 Web 服务器提供了一种标准协议，使其能够执行类似于在服务器上运行的命令行界面程序（即控制台应用程序），从而动态生成网页。这类程序被称为 CGI 脚本或简称为 CGI。服务器具体如何执行脚本由其自身决定。通常情况下，CGI 脚本会在收到请求时立即执行并生成 HTML 内容。

CGI is the part of the Web server that can communicate with other programs running on the server. With CGI, the Web server can call up a program, while passing user-specific data to the program (such as what host the user is connecting from, or input the user has supplied using HTML form syntax). The program then processes that data and the server passes the program's response back to the Web browser.
CGI 是 Web 服务器的一部分，能够与服务器上运行的其他程序进行通信。通过 CGI，Web 服务器可以调用某个程序，同时将用户特定的数据传递给该程序（例如用户连接的主机信息，或用户通过 HTML 表单语法输入的参数）。该程序处理完数据后，服务器会将程序的响应结果传回给 Web 浏览器。

Past paper Questions  历年真题

A search engine is accessed through a browser on the user’s computer.
搜索引擎通过用户计算机上的浏览器进行访问。
The list of contents/results returned to the user is known as search engine results page (SERP)
返回给用户的内容/结果列表被称为搜索引擎结果页面（SERP）

C.2.3 Outline the principles of searching algorithms used by search engines
C.2.3 概述搜索引擎使用的搜索算法原理

HITS algorithm  HITS 算法

C.2.12 future challenges to search engines as the web continues to grow
C.2.12 随着网络持续发展搜索引擎将面临的未来挑战

Search engines must be fast enough to crawl the exploding volume of new Web pages in order to provide the most up-to-date information. As the number of pages on the Web grows, so will the number of results search engines return. So, it will be increasingly important for search engines to present results in a way that makes it quick and easy for users to find exactly the information they’re looking for. Search engines have to overcome both these challenges.
搜索引擎必须足够快速地爬取激增的新网页数量，以提供最新的信息。随着网络上网页数量的增长，搜索引擎返回的结果数量也会增加。因此，搜索引擎以快速、简便的方式呈现结果，让用户准确找到所需信息将变得越来越重要。搜索引擎必须克服这两大挑战。

C.3 Distributed approaches to the web
C.3 网络的分布式方法

Link to Peer-to-peer Slides and ubiquitous Computing
链接至 Peer-to-peer 幻灯片与 ubiquitous Computing

Link to Grid Computing Slides
网格计算幻灯片链接

C.3.1 Define the terms: mobile computing, ubiquitous computing, peer-2-peer network, grid computing
C.3.1 定义以下术语：移动计算（mobile computing）、普适计算（ubiquitous computing）、点对点网络（peer-2-peer network）、网格计算（grid computing）

What is Grid Computing?  什么是网格计算？

the grid that will enable the public to exploit data storage and computer power over the Internet analogous to the electric power utility (a ubiquitous commodity).
这种网格将使公众能够通过互联网利用数据存储和计算能力，类似于电力设施（一种无处不在的商品）。

Normally, a computer can only operate within the limitations of its own resources. There's an upper limit to how fast it can complete an operation or how much information it can store. Most computers are upgradeable, which means it's possible to add more power or capacity to a single computer, but that's still just an incremental increase in performance.
通常，计算机只能在自身资源的限制范围内运行。其完成操作的速度或存储信息的量都存在上限。大多数计算机都可以升级，这意味着可以为单台计算机增加更多性能或容量，但这仍然只是性能的渐进式提升。

Grid computing systems link computer resources together in a way that lets someone use one computer to access and leverage the collected power of all the computers in the system. To the individual user, it's as if the user's computer has transformed into a supercomputer.
网格计算系统以某种方式将计算机资源链接在一起，使得用户能够通过一台计算机访问并利用系统中所有计算机的集体计算能力。对于个人用户而言，这就像是他们的计算机已经转变为一台超级计算机。

Grid Computing Lexicon  网格计算术语表

Interoperability: The ability for software to operate within completely different environments. For example, a computer network might include both PCs and Macintosh computers. Without interoperable software, these computers wouldn't be able to work together because of their different operating systems and architecture.
互操作性：软件在不同环境中运行的能力。例如，计算机网络可能同时包含 PC 和 Macintosh 计算机。如果没有互操作性软件，这些计算机将无法协作，因为它们使用不同的操作系统和架构。

Open standards: A technique of creating publically available standards. Unlike proprietary standards, which can belong exclusively to a single entity, anyone can adopt and use an open standard. Applications based on the same open standards are easier to integrate than ones built on different proprietary standards.
开放标准：一种创建公开可用标准的技术。与专有标准（可专属于单一实体）不同，任何人都可以采用和使用开放标准。基于相同开放标准的应用程序比基于不同专有标准的应用程序更易于集成。

At least one computer, usually a server, which handles all the administrative duties for the system. Many people refer to this kind of computer as a control node. Other application and Web servers (both physical and virtual) provide specific services to the system.text here...
至少有一台计算机（通常为服务器）负责处理系统的所有管理职责。许多人将这类计算机称为控制节点。其他应用服务器和 Web 服务器（包括物理服务器和虚拟服务器）则为系统提供特定服务。

Cluster: A group of networked computers sharing the same set of resources.
Cluster: 共享同一组资源的一组联网计算机。

What is ubiquitous Computing?
什么是 Ubiquitous Computing？

C.3.2 Compare the major features of: • mobile computing • ubiquitous computing • peer-2-peer network • grid computing
C.3.2 比较以下各项的主要特征： • 移动计算（mobile computing） • 普适计算（ubiquitous computing） • 对等网络（peer-2-peer network） • 网格计算（grid computing）

Mobile computing  移动计算

Mobile Computing is a technology that allows transmission of data, voice and video via a computer or any other wireless enabled device without having to be connected to a fixed physical link. The main concept involves,
移动计算是一种技术，允许通过计算机或任何其他支持无线的设备传输数据、语音和视频，而无需连接至固定物理链路。其核心理念包括：

• Mobile communication  移动通信
• Mobile hardware: portable laptops, smartphones, tablet Pc’s, Personal Digital Assistants
  移动硬件：便携式笔记本电脑、智能手机、平板电脑、个人数字助理
• Mobile software  移动软件

Characteristics  特点

Portability: The Ability to move a device within a learning environment or to different environments with ease.
便携性：能够轻松将设备在学习环境内或不同环境之间移动。

Social Interactivity: The ability to share data and collaboration between users.
Social Interactivity：在用户之间共享数据并进行协作的能力。

Context Sensitivity: The ability to gather and respond to real or simulated data unique to a current location, environment, or time.
上下文敏感性（Context Sensitivity）：收集和响应特定于当前位置、环境或时间的真实或模拟数据的能力。

Connectivity: The ability to be digitally connected for the purpose of communication of data in any environment.
连接性：在任何环境下为进行数据通信而保持数字化连接的能力。

Individual: The ability to use the technology to provide scaffolding on difficult activities and lesson customization for individual learners.
Individual: 利用技术为个体学习者在困难活动中提供脚手架支持并进行课程定制的能力。

Advantages  优点

• Increase in productivity- as they would be used out in the field of various companies, as it would reduce the time and cost for the client.
  生产力提高——因为它们将被应用于不同公司的实际业务中，从而减少客户的时间和成本。
• Entertainment- Mobile devices can be used for the entertainment purposes, for personal and even presentations to people and clients.
  娱乐——移动设备可用于娱乐目的，既可用于个人用途，也可用于向他人和客户进行展示。
• Cloud computing- Saving documents on online server and being able to access them anytime and anywhere when you have a connection to the internet.
  云计算——将文档保存在在线服务器上，在连接到互联网时能够随时随地访问它们。
• Portability- not restricted to one location in order for you to get jobs done or even access email on the go.
  可移植性——不受限于单一地点，以便您完成任务，甚至在外出时访问电子邮件。

Disadvantages  缺点

• Quality connectivity- mobile devices will need to either WIFI connectivity or mobile network. such as GPRS, 3G
  高质量连接——移动设备需要具备 WIFI 连接或移动网络连接，例如 GPRS、3G。
• Security concerns- Mobile VPNs are unsafe to connect to, and also syncing devices might also lead to security concerns. accessing a WiFi network can also be risky because WPA and WEP security can be bypassed easily.
  安全问题——移动虚拟专用网络（VPN）的连接存在安全隐患，设备同步也可能引发安全问题。连接 WiFi 网络同样存在风险，因为 WPA 和 WEP 安全协议很容易被绕过。
• Power consumption, due to the use of the batteries
  因使用电池而产生的功耗

Ubiquitous computing (pervasive computing)
普适计算（普及计算）

Definition  定义

Ubiquitous computing is the idea of computing being available everywhere and anytime.
普适计算是指计算能力随时随地可用的理念。

• Idea of invisible computing
  隐形计算理念
• Embedded computing (microprocessors)
  嵌入式计算（微处理器）
  • Need for low cost, low power computing with connectivity
    具备连接能力的低成本、低功耗计算需求
• Usually includes a variety of sensors
  通常包含多种传感器
• Smart designs: different architectures
  智能设计：不同架构
  • Need for standards and protocols
    对标准与协议的需求

Peer-to-peer computing  对等计算

Definition  定义

PCs handling data locally instead of servers(becomes client and server); individual computers connect directly and communicating with each other as equals.
PC 在本地处理数据而非依赖服务器（成为客户端和服务器）；各计算机直接连接并以对等的方式相互通信。

“A peer-to-peer (P2P) network is created when two or more PCs are connected and share resources without going through a separate server computer”
点对点（P2P）网络是在两台或多台个人计算机连接并共享资源时建立的，无需通过独立的服务器计算机

Characteristics:  特点：

• Decentralized  去中心化
  • If one peer falls out not the whole network affected
    如果一个对等节点掉线，整个网络不会受到影响
  • But data recovery of one peer that is shutdown is not possible
    但无法恢复已关闭的一个对等节点的数据
    • Requires independent backup
      需要独立备份
• Each peer acts as client and server
  每个对等节点同时充当客户端和服务器
• Resources and contents shared across all peers and shared faster than client <-> server
  在所有对等节点之间共享的资源和内容，其共享速度比客户端<->服务器模式更快
• Has to be done by some software to enable this
  必须通过某些软件来实现这一点
• Malware can be faster distributed
  恶意软件可以更快地传播

C.3.3 Distinguish between interoperability and open standards.
C.3.3 区分互操作性与开放标准。

Interoperability can be defined as “the ability of two or more systems or components to exchange information and to use the information that has been exchanged”. In order for systems to be able to communicate they need to agree on how to proceed and for this reason standards are necessary. A single company could work on different systems that are interoperable through private standards only known to the company itself. However, for real interoperability between different systems open standards become necessary.
互操作性可定义为“两个或多个系统或组件交换信息并使用所交换信息的能力”。为了让系统能够通信，它们需要就如何操作达成一致，因此标准是必要的。一家公司可以开发通过仅其自身知晓的私有标准实现互操作的不同系统。然而，要实现不同系统间真正的互操作性，开放标准变得不可或缺。

Open standards are standards that follow certain open principles. Definitions vary, but the most common principles are:
开放标准是指遵循某些开放准则的标准。具体定义各不相同，但最常见的准则包括：

public availability  公开可用性
collaborative development, usually through some organization such as the World Wide Web Consortium (W3C) or the IEEE
协作开发，通常通过某些组织，例如万维网联盟（W3C）或 IEEE
royalty-free  免版税
voluntary adoption  自愿采用
The need for open standards is described well by W3C director and WWW inventor Tim Berners-Lee who said that “the decision to make the Web an open system was necessary for it to be universal. You can’t propose that something be a universal space and at the same time keep control of it.”
万维网发明者、W3C 主任蒂姆·伯纳斯-李很好地阐述了开放标准的必要性，他指出："决定让万维网成为一个开放系统是它能够实现普遍性的必要条件。你不能既提议某事物成为通用空间，同时又保持对它的控制。"

Some examples of open standards include:
一些开放标准的例子包括：

file formats, e.g. HTML, PNG, SVG
文件格式，例如 HTML、PNG、SVG
protocols, e.g. IP, TCP  协议，例如 IP、TCP
programming languages, e.g. JavaScript(ECMAScript)
编程语言，例如 JavaScript(ECMAScript)

C.3.4 Describe the range of hardware used by distributed networks.
C.3.4 描述分布式网络所使用的各类硬件。

This of course depends on the different types of distributed systems, but most generally speaking on a low level multiple CPUs need to be interconnected through some network, while at a higher level processes need to be able to communicate and coordinate. For each approach to distributed system, more specific types of hardware could be used:
这当然取决于不同类型的分布式系统，但广义而言，在低层次上需要通过网络互连多个 CPU，而在高层次上进程需要能够相互通信和协调。对于每种分布式系统实现方式，可能需要使用更具体的硬件类型：

• Mobile computing: wearables (e.g. Fitbit ), smartphones, tablets, laptops, but also transmitters and other hardware involved in cellular networks
  移动计算：可穿戴设备（例如 Fitbit ）、智能手机、平板电脑、笔记本电脑，以及涉及蜂窝网络的发射器和其他硬件
• Ubiquitous computing: embedded devices, IoT devices, mobile computing devices, networking devices
  普适计算：嵌入式设备、IoT 设备、移动计算设备、网络设备
• Peer-to-peer computing: usually PCs, but can include dedicated servers for coordination
  Peer-to-peer computing：通常是 PC，但可以包含用于协调的专用服务器
• Grid computing: PCs and servers
  网格计算：个人计算机与服务器
• Content delivery networks (CDNs) is a system of distributed servers. They can cache content and speed up the delivery of content on a global scale
  内容分发网络（CDNs）是一个分布式服务器系统。它们能够缓存内容并在全球范围内加速内容的分发。
• Blockchain technology(e.g. Bitcoin, Ethereum) are decentralized and based on multiple peers, which can be PCs but also server farms
  区块链技术(如 Bitcoin、Ethereum)具有去中心化特性，基于多个对等节点运行，这些节点既可以是个人电脑，也可以是服务器群。
• Botnets can probably be considered a form of distributed computing as well, consisting of hacked devices, such as routers or PCs
  僵尸网络或许也可被视为一种分布式计算形式，由被入侵的设备（如路由器或 PC）组成

Distributed systems consist of many different nodes that interact with each other. For this reason they are decentralized by design, which you can see in this comparison.
分布式系统由许多相互交互的不同节点组成。因此，它们在设计上是去中心化的，通过这种比较可以看出这一点。

Therefore, the importance of distributed systems for a decentralized web lies in their benefits and disadvantages compared to classic centralized client-server models.
因此，分布式系统对去中心化网络的重要性，在于其相较于经典集中式客户端-服务器模式的优势与劣势。

Benefits  优势

• higher fault tolerance  更高的容错性
• stability  稳定性
• scalability  可扩展性
• privacy  隐私
• data portability is more likely
  数据可移植性更有可能
• independence from large corporations such as Facebook, Google, Apple or Microsoft
  独立于诸如 Facebook、Google、Apple 或 Microsoft 等大型企业
• potential for high performance systems
  高性能系统的潜力

Disadvantages  缺点

• more difficult to maintain
  更难以维护
• harder to develop and implement
  更难以开发和实施
• increased need for security
  安全需求的增长

Personal conclusion  个人结论

While some decentralized systems such as Bitcoins are gaining traction and some other systems like Git or Bittorrent have been around for a good time already, most part of the internet is still centralized, as most web applications follow the client-server model, which is further encouraged by corporations wanting to make profit. I found this post from Brewster Kahle’s Blog on the topic very interesting.
尽管比特币等一些去中心化系统逐渐流行，Git 或 BitTorrent 等其他系统也已存在多年，但互联网的大部分仍处于中心化状态，因为大多数网络应用遵循客户端-服务器模式，这种模式更被追求盈利的企业所推崇。我发现 Brewster Kahle 博客中关于这个话题的这篇文章非常有趣。

C.4.7 Explain why the web may be creating unregulated monopolies
C.4.7 解释网络可能正在催生不受监管的垄断的原因

In theory the world wide web should be a free place where anybody can have a website. However, hosting a website usually comes with a cost - registering a domain name, getting a hosting service or investing in servers oneself, creating and maintaining the website (requires technical knowledge or the cost of hiring a web developer). In addition, to reach an audience further marketing through SEO (see C.2) is usually necessary to get good rankings in search engine results. This means that for the normal individual a traditional website is not the best option. A better alternative is to publish content on an existing platform, e.g. micro blogging on Twitter, blogging on WordPress or Blogspot, sharing social updates on Facebook, sharing photos on Flickr, etc. . This comes with improved comfort for users.
理论上，万维网应该是一个自由的空间，任何人都可以拥有网站。然而，托管网站通常需要成本——注册域名、获取托管服务或自行投资服务器、创建和维护网站（需要技术知识或雇佣网页开发者的成本）。此外，为了触达受众，通常需要通过 SEO（见 C.2）进行进一步营销，才能在搜索引擎结果中获得良好排名。这意味着对于普通个人而言，传统网站并非最佳选择。更好的替代方案是在现有平台上发布内容，例如在 Twitter 进行微博客、在 WordPress 或 Blogspot 写博客、在 Facebook 分享社交动态、在 Flickr 分享照片等。这为用户带来了更高的便利性。

However, it easily leads to unregulated monopolies in the market because users usually stick to one platform. Tim Berners-Lee describes today’s social networks as centralized silos, which hold all user information in one place. This can be a problem, as such monopolies usually control a large quantity of personal information which could be misused commercially or stolen by hackers. There are certainly many more concerns which won’t fit into the scope of this site.
然而，这很容易导致市场上出现不受监管的垄断，因为用户通常只使用一个平台。Tim Berners-Lee 将当今的社交网络描述为集中化的信息孤岛，将所有用户信息储存在单一位置。这会带来隐患，因为此类垄断平台通常控制着大量个人信息，这些信息可能被商业滥用或被黑客窃取。当然还有更多超出本网站讨论范围的潜在问题。

C.4.8 Decentralized and democratic web
C.4.8 去中心化与民主化网络

Search Bubbles  过滤气泡

A Filter Bubble Demonstration - Try this at home!
过滤气泡（Filter Bubble）演示——在家试试看！

One way to see how filter bubbles work with search engines that do personalization (like Google) is to take a word that can have multiple meanings in different contexts and build up different search histories using those contexts. Then, when you search for the same word after having built up different search histories, the search engine should return results that look a bit different.
要了解过滤气泡如何在支持个性化定制的搜索引擎（如 Google）中发挥作用，一种方法是选取一个在不同语境下具有多重含义的词汇，并基于这些语境构建不同的搜索历史记录。随后，当您在使用不同搜索历史记录后搜索同一词汇时，搜索引擎应该会返回略有差异的搜索结果。

For this demonstration to work, you need to be sure to clear your search history before you start each round. This works even better if you have 2 or 3 people working side by side at different computers. That way you can compare the results more easily.
为确保此演示顺利进行，你需要在每轮开始前清除搜索历史记录。若有 2 至 3 人同时操作不同电脑，效果更佳，这样能更方便地比较结果。

Try this with the word Tea.
用“茶”这个词试试看。

1. Have someone build a search history using names of countries where tea is popularor names of countries where teas orgininated. Remember, do not use the word "tea" as a search term quite yet. Examples would be England, Japan, China, Latin America, etc.
1. 让人建立一个搜索历史，使用茶受欢迎的国家名称或茶起源的国家名称。记住，暂时不要使用"tea"这个词作为搜索词。例如 England、Japan、China、Latin America 等。

2. Have another person build a search history using different spices, herbs, and flowersthat make up common teas. Examples would be roses, cinammon, chrysanthemum, lavender, etc.
2. 让另一个人使用构成常见茶的不同香料、草药和花卉来构建搜索历史。例如玫瑰、肉桂、菊花、薰衣草等。

3. Have a third person search for anything related to politics, such as names of political parties (not the Tea Party just yet, though!), names of political movements, words like "activism," or "conservative" and "liberal."
3. 让第三方人员搜索与政治相关的任何内容，例如政党名称（不过暂时不包括 Tea Party！）、政治运动的名称，以及诸如“activism”、“conservative”和“liberal”等词汇。

4. When you are performing these searches, click on some of the results (preferably general ones that might somehow later be connected to tea!). This will contribute to your search history.
4. 当你执行这些搜索时，点击部分结果（最好是稍后可能与茶相关的通用结果！）。这将有助于丰富你的搜索历史记录。

5. Finally, have everyone search for the word "Tea." Have fun comparing results!
5. 最后，让所有人搜索“Tea”这个词。愉快地比较结果吧！

Note: Your results may still look very similar; the differences may be subtle. Whether or not the filter bubble is really something to be concerned about will be discussed in the next tab.
注意：您的结果可能看起来仍然非常相似；差异可能很细微。信息茧房是否真的值得担忧，将在下一标签页中讨论。

Who does this?  谁来做这件事？

These are just a few of the websites that tailor results to you and your clicking history:
以下是根据您和您的点击历史定制结果的几个网站示例：

Link to PowerPoint Slides
PowerPoint 幻灯片链接

Questions on Directed Graphs
有关有向图的问题

(a) Name an edge you could add or delete from the graph in Figure 13.8 so as to increase the size of the largest strongly connected component.
(a) 请说出你可以从图 13.8 中增加或删除的一条边，以增大最大强连通组件的规模。

(b) Name an edge you could add or delete from the graph in Figure 13.8 so as to increase the size of the set IN
(b) 请指出在图 13.8 中你可以添加或删除的一条边，以使集合 IN 的规模增大

(c) Name an edge you could add or delete from the graph in Figure 13.8 so as to increase the size of the set OUT.
(c) 请指出在图 13.8 中你可以添加或删除的一条边，以增大集合 OUT 的大小。

C.5.2 Outline the difference between the web graph and sub-graphs.
C.5.2 概述网络图（web graph）与子图（sub-graphs）之间的区别。

Web graph

• Web graph describes the directed links between web pages in the WWW.
  Web 图描述了 WWW 中网页之间的有向链接。
• It is a directed graph with directed edges
  它是一个具有有向边的有向图
  • Page A has a hyperlink to Page B, creating a directed edge from Page A to Page B
    页面 A 有一个指向页面 B 的超链接，从而创建了从页面 A 到页面 B 的有向边

Sub-Graph  子图

• A set of pages that are part of the internet
  作为互联网组成部分的一组页面
• Can be a set of pages linked to a specific topic ex.: Wikipedia -> one topic but references(and hyperlinks) to other web pages
  可以是一组链接到特定主题的页面，例如：Wikipedia -> 一个主题但包含对其他网页的引用（和超链接）
• Can be a set of pages that deal with part of an organization
  可以是一组处理组织部分事务的页面

C.5.3 Describe the main features of the web graph such as bowtie structure, strongly connected core (SCC), diameter.
C.5.3 描述网络图的主要特征，例如领结结构、强连通核心（SCC）、直径。

C.5.4 Explain the role of graph theory in determining the connectivity of the web.
C.5.4 解释图论在确定网络连通性中的作用。

Connectivity  连通性
This is just a metric to discuss how well parts of a network connect to each other.
这只是一个用于讨论网络各部分之间连接程度的指标。

Small world graph  小世界图
This is a mathematical graph whereas not all nodes are directly neighbors, but any given pair of nodes can be reached by a small number of hops or better said with just a few links. This is due to nodes being interconnected through interconnected hubs.
这是一个数学图，虽然并非所有节点都是直接邻居，但任意两个节点之间只需少量跳跃（或更准确地说，仅需几个链接）即可到达。这是由于节点通过相互连接的枢纽实现互连。

2 Properties of the small world graph:
2 小世界图的属性：
Mean shortest-path length will be small
平均最短路径长度会很小
Most pairs of nodes will be connected by at least one short path
大多数节点对之间至少存在一条短路径相连
many clusters (highly connected subgraphs)
大量集群（高度连通的子图）
Analogy: airlines flight whereas you can reach any city most likely in just under three flights.
类比：航空公司的航班，你很可能只需不到三次航班就能到达任何城市。
Examples: network of our brain neurons
我们大脑神经元的网络
Maximizes connectivity  最大化连接性
Minimizes # of connections
最小化连接数

6 degrees of separation  六度分隔
This originates from the idea that any human in the world is related in some way over 6 or less connections (steps). This idea can be taken further in a more general perspective on a graph, whereas any given pair of nodes within the network can be reached with just a maximum of 6 steps.
这一概念源于世界上任何两个人之间都能通过不超过 6 个连接（步骤）以某种方式建立联系的观点。从图的更普遍视角来看，这一观点可以进一步延伸为：网络中的任意两个节点最多只需 6 步即可相互到达。

The idea itself can be applied to the web graph, suggesting high connectivity regardless of big size.
这一理念本身可应用于 web graph，表明即使规模庞大，仍具备高连通性。

Not necessarily small world graph
不一定是 small world graph
High connectivity between all nodes
所有节点之间的高连接性
Web diameter (and its importance)
Web diameter (and its importance) 网络直径（及其重要性）
The diameter of the web graph has no standard definition, but is usually considered to be the average distance (as each edge has the same path length, this would be steps) between two random nodes.
网络图的直径没有标准定义，但通常被认为是两个随机节点之间的平均距离（由于每条边具有相同的路径长度，这里指步数）。

This is important because it is an indicator of how quickly one can reach some page from any starting page in average. This is of importance for crawler, which want to index as many pages as possible in the shortest path.
这一点很重要，因为它是衡量从任意起始页面平均能多快到达某个页面的指标。这对于爬虫程序（crawler）尤为重要，因为它们希望在最短路径内索引尽可能多的页面。

average distance between two random nodes (pages)
两个随机节点（pages）之间的平均距离
important for crawlers to have a guide of how many steps it should take to reach a page
对爬虫而言，拥有指引其到达页面所需步骤数的指南至关重要
a factor to consider, is if the path is directed or undirected
需要考虑的一个因素是路径是定向（directed）还是非定向（undirected）的
often there is no direct path between nodes
节点之间通常不存在直接路径
Importance of hubs and authorities (link to C.2.3)
枢纽与权威的重要性（链接至 C.2.3）
Hubs and authorities have special characteristics:
枢纽节点和权威节点具有特殊的特征：

Hubs: have a large number of outgoing links
Hubs：拥有大量出站链接
Authorities: have a large number of incoming links
权威页面：拥有大量入站链接
For connectivity, this means that a larger number of hubs improves connectivity, while authorities are more likely to decrease connectivity as they usually do not link to many other pages.
就连接性而言，这意味着枢纽数量越多，连接性越好，而权威节点通常不会链接到许多其他页面，因此更可能降低连接性。

C.5.5 Explain that search engines and web crawling use the web graph to access information.
C.5.5 解释搜索引擎和网络爬虫如何利用网络图来访问信息。

C.5.6 Discuss whether power laws are appropriate to predict the development of the web.
C.5.6 讨论幂律是否适用于预测网络的发展。

C.6.1 Define the term semantic web 
C.6.1 定义术语语义网

The Semantic Web is an extension of the current web in which information is given well-defined meaning, better enabling computers and people to work in cooperation.
语义网是当前万维网的扩展，其中信息被赋予明确定义的含义，从而更好地促进计算机和人类协同工作。

a proposed development of the World Wide Web in which data in web pages is structured and tagged in such a way that it can be read directly by computers
万维网的一项提议发展，其中网页中的数据被结构化和标记，使计算机可以直接读取

The Semantic web is an extension of the current web where data in webpages is structured and tagged to give it semantic meaning and make it machine-understandable, allowing computers and people to work in cooperation
语义网是现有网络的一个扩展，其中网页中的数据经过结构化和标记，赋予其语义意义并使其能够被机器理解，从而使计算机和人类能够协作

C.6.2 Distinguish between the text-web and the multimedia-web 
C.6.2 区分文本网络（text-web）与多媒体网络（multimedia-web）

The traditional web is seen as being text based, the semantic web is multimedia based. Text-web - “read-only” Web
传统网络被视为以文本为基础，而语义网则以多媒体为基础。文本网络——"只读"网络
Unlike text-web, multimedia web pages use different forms of graphic content
与 text-web 不同，多媒体网页使用不同形式的图形内容

C.6.3 Aims of semantic web
C.6.3 语义网的目标

Ultimate aim is to allow computers to do more useful work and allow people and computers to work together
最终目标是使计算机能够完成更多有用的工作，并使人和计算机能够协同工作

C.6.4 Distinguish between an ontology and folksonomy
C.6.4 区分本体与大众分类法

[tip: also read C.6.5 in conjunction to better understand C.6.4]
[提示：同时阅读 C.6.5 以结合理解 C.6.4]

References: http://www.sims.monash.edu.au/subjects/ims2603/resources/week7/7.1.pdf
参考文献：http://www.sims.monash.edu.au/subjects/ims2603/resources/week7/7.1.pdf

important to understand very simply classification, folksonomy, and its drawbacks
有必要简单了解分类、大众分类法及其缺点

http://www.ijodls.in/uploads/3/6/0/3/3603729/3_mohmedhanif__29-35_.pdf 

tagging and folksonomy  标签和分众分类法
http://www.cl.cam.ac.uk/~aac10/R207/ontology_vs_folksonomy.pdf 

Ontology- A collection of names for a particular concept, like our music instruments assignment and relation types, organised in a type, sub-type and sub-sub type as so on
本体论（Ontology）- 针对某一特定概念（如我们的音乐器材作业）的名称集合及关系类型，按类型、子类型、子子类型等层次结构进行组织

Folksonomy - Folksonomy is the result of personal free tagging of information and objects (anything with a URL) for one's own retrieval. The tagging is done in a social environment (usually shared and open to others). Folksonomy is created from the act of tagging by the person consuming the information
Folksonomy - Folksonomy 是个人在社交环境（通常与他人共享并开放）中为便于自身检索而对信息和对象（任何带有 URL 的事物）进行自由标注的结果。该分类体系产生于信息消费者实施标注行为的过程中。

Folksonomy is a system of classification derived from the practice and method of collaboratively creating and translating tags to annotate and categorize content. Ontology is hard to implement on a large scale and isn’t always web based. It is Key for the semantic web because of high expressive power. Folksonomy is created by users as well as being quick and easy to implement. It is used on a large scale for document collections. Most of the time its web based and important in web 2.0
分众分类法（Folksonomy）是一种通过协作创建和转换标签来注释与分类内容的分类系统。本体论（Ontology）难以大规模实施且不总是基于网络。因其高表达能力，它是语义网的关键。分众分类法由用户创建，实施快速简便，被大规模应用于文档集合管理，通常基于网络且在 Web 2.0 中具有重要地位。

C.6.5 Describe how folksonomies and emergent social structures are changing the web
C.6.5 描述分众分类（folksonomies）和涌现的社会结构如何改变网络

Folksonomies and social structures are changing the web because they are a system of classification. Folksonomy is created by users as well as being quick and easy to implement. If we look at facebook for example, most of the content on there is created by the user. They are able to upload images, create statuses and much more. They are changing the web because all the content is determined by the user as opposed to the owners of the companies.
分众分类法（Folksonomies）与社会结构正在改变网络，因为它们本身即构成一种分类系统。分众分类法由用户创建且易于快速实施。以 Facebook 为例，其平台上的大部分内容均由用户生成。用户能够上传图片、发布状态更新等多样化操作。这些行为正在重塑网络生态，因为所有内容均由用户而非企业所有者所决定。
An example of folksonomies is the tag system in image sites or hashtags in social media. Users are defining more and more tags and as the volume of users tagging increases, the accuracy of tags increases such that the web is becoming more and more precise.
Tagging increases user participation in the web while enhancing searching and semantics of the web.
大众分类法（folksonomies）的一个例子是图片网站中的标签系统或社交媒体中的标签（hashtag）。用户正在定义越来越多的标签，随着用户标注量的增加，标签的准确性也在提升，使得网络变得越来越精确。标签化在增强网络搜索与语义功能的同时，也提高了用户对网络的参与度。

Folksonomy in social structures refers to users tagging media on social sites, for example tagging a picture of a cat as cute and animal. On sites like Flickr when more and more people tag a photo, it helps change the web by introducing semantic meaning to media, meaning created by users themselves. This is only possible through these emerging structures like Facebook, Flickr, etc. that allow us to create folksonomies through tagging
社交结构中的分众分类（Folksonomy）指用户在社交网站上对媒体进行标签分类的行为，例如将一张猫的照片标记为"cute"和"animal"。在 Flickr 等平台上，当越来越多用户为照片添加标签时，通过用户自身创建的语义（semantic meaning），这种集体标注行为帮助改变了网络媒体形态。这种变革只有通过 Facebook、Flickr 等新兴社交平台的结构才得以实现，这些平台允许我们通过标签创建分众分类体系。

Folksonomy is a key part of Web 2.0 since it allows users to interact with the system and organize the wealth of information online. Most of the Web 2.0 technologies now have the flexibility to allow user to describe the content using keywords, categories, or labels. Note that these keywords, labels, tags, etc. are actually being used in many services on the web now.
分众分类（Folksonomy）是 Web 2.0 的关键组成部分，因为它允许用户与系统互动并组织海量在线信息。当前大多数 Web 2.0 技术都能灵活地让用户使用关键词、分类或标签来描述内容。值得注意的是，这些关键词、标签等元素如今已被广泛应用于众多网络服务中。
This helps in identifying the content from the user context and helps for future retrieval. Folksonomy is important field of web 2.0 services. User index resources by themselves with free keywords, which are called tags. There are a lot of services online, especially for index bookmarks. Del.icio.us is here the most famous one
这有助于从用户上下文中识别内容，并为未来的检索提供便利。大众分类（Folksonomy）是 Web 2.0 服务的重要领域。用户使用自由关键词自行索引资源，这些关键词被称为标签。在线有许多此类服务，尤其是用于索引书签的服务。Del.icio.us 是其中最著名的一个。

C.6.6 Explain why there needs to be a balance between expressivity and usability on the semantic web.
C.6.6 解释为什么语义网需要在表达力与可用性之间保持平衡。

C.6.7 Evaluate methods of searching for information on the web.
C.6.7 评估在网络上搜索信息的方法。

C.6.8 Distinguish between ambient intelligence and collective intelligence
C.6.8 区分环境智能与集体智能

Slide to Ambient / Collective Intelligence  Click Here
滑动至 Ambient/Collective Intelligence 点击此处

C.6.9 Discuss how ambient intelligence can be used to support people.
C.6.9 讨论环境智能如何用于支持人们。

C.6.10 Explain how collective intelligence can be applied to complex issues.
C.6.10 解释如何将集体智慧应用于复杂问题。

Further Reading   延伸阅读

http://www.ftsm.ukm.my/ss/Book/EVOLUTION%20OF%20WWW.pdf

https://eprints.soton.ac.uk/272374/1/evolvingwebfinal.pdf

http://dig.csail.mit.edu/2007/Papers/AIMagazine/fractal-paper.pdf