SEO简明教程 第一章 分析搜索引擎概貌（2）

搜索引擎和网络目录调查

搜索引擎已经是搜索系统或搜索网站的主要术语，在进一步阅读后续内容之前，您需要了解一些搜索术语之间的区别，这些术语您后面将会碰到。基本上，您需要了解四种搜索术语：

一 搜索目录或搜索引擎

搜索目录或搜索引擎是您将要遇到的主要搜索工具。从根本上讲，搜索引擎这个术语是指某些搜索目录，它拥有大规模的数据库，数据库中包含了许多独立网站的信息。

大型的搜索目录公司拥有数千台电脑，在这些电脑上运行着一种称为网络蜘蛛或者机器人的程序，这些网络蜘蛛从网络上抓取网页并分析网页的内容。这些网络蜘蛛通常并不是把每一个页面中的所有信息或者某一个网站中的所有内容都抓取下来，不过它们还是抓取了大量的信息，并使用复杂的算法（复杂的计算公式）来索引这些信息。Google，如图1-1所示，是世界上最流行的搜索引擎，紧跟其后的是Yahoo！和MSN。

图1-1 Google，世界上最流行的搜索引擎产生的查询结果

附注：索引比赛

2005年晚些时候，Yahoo！(www.yahoo.com) 声称：它的索引量大约是二十亿个页面和两亿张图片以及五千万个音频和视频页面。Google(www.google.com)曾经在它的主页上声明自己实际索引的页面数量—–一度达到15亿个页面，不过Google并不想跟Yahoo！玩“我家东东比你多”的游戏。

英文原文：

Investigating Search Engines and Directories

The term search engine has become the predominant term for search system

or search site, but before reading any further, you need to understand the different types of search, um, thingies, you’re going to run across. Basically, youneed to know about four thingies.

Search indexes or search engines

Search indexes or engines are the predominant type of search tools you’ll run across. Originally, the term search engine referred to some kind of search index, a huge database containing information from individual Web sites.

Large search-index companies own thousands of computers that use software known as spiders or robots (or just plain bots) to grab Web pages and read the information stored in them. These systems don’t always grab all the information on each page or all the pages in a Web site, but they grab a significant amount of information and use complex algorithms — calculations based on complicated formulae — to index that information. Google, shown in Figure 1-1, is the world’s most popular search engine, closely followed by Yahoo! and MSN.

Index envy

Late in 2005, Yahoo! (www.yahoo.com) claimed that its index contained information about almost 20 billion pages, along with almost 2 billion images and 50 million audio and video pages. Google (www.google.com) used to actually state on its home page how many pages it indexed — they reached 15 billion or so at one point — but decided not to play the “mine is bigger than yours” game with Yahoo!

SEO教程中文版翻译自：Search Engine Optimization For Dummies, 2nd Edition。 By Peter Kent

原创文章如转载，请注明：转载自网络海洋的博客 [ http://www.mycnweb.com/ ]