语言教学 | 普渡大学写作教学系列Research&Citation8-Searching Online(1)

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1、Searching Online: Overview

Searching online can be both beneficial and frustrating. You may find vast amounts of information, or you may not find the kinds of information you're looking for. Searching online will provide you with a wealth of information, but not all of it will be useful or of the highest quality.

The internet is a superb resource, but it doesn't contain all the information that you can find at a library or through library online resources. You should not limit your search to what is on the Internet, and you cannot expect search engines to find everything that is on the Web.

The Internet is a complex and ever-evolving place. New sites and media are not automatically found by search engines. Indexing is the term for the process whereby webcrawlers find and include new pages and other media in their search results. However, search engines still only index a fraction of what is available on the Internet and not all of it is up to date. Search engines may only "crawl" sites (or revisit them for purposes of indexing) every month or less; information that has been updated since that time will be invisible to the search engines.

Finally, search engines don't always search the entire page; many search engines will only index the first 100 to 500k of each page. So there might be valuable information that is being overlooked by a search engine, even in pages that are indexed.

Additionally, not all of the information located on the Internet can be found via search engines. Researchers Chris Sherman and Gary Price call this information the "invisible Web" (another name that is frequently used is the "deep Web"). Invisible Web information includes certain file formats, information contained in databases, and pages omitted from search engines.

With this in mind, knowing a few search strategies and hints can make the search more profitable. This guide provides information on the different ways of locating material online, including using search engines, searching the invisible Web, and using Web directories.

2、How the Internet and Search Engines Work

The Internet is made up of a vast amount of computers networked throughout the world via data lines or wireless routers. New computers and websites are added every day, and no larger organizational system exists to document and catalogue them all. The Internet is a dynamic, growing, and changing system, which makes navigating it or searching it thoroughly difficult.

This is where search engines and Web directories come in. Search engines, such as Google or Yahoo, are large databases of information that store and retrieve relevant website results based on keywords. Web directories, such as DMOZ, are attempts to organize the best of the existing websites into categories and subcategories. No search engine or web directory will have the same sites listed in the same order, and none will have all of the possible sites on the Internet listed. Furthermore, the ranking of a website within a search engine (i.e. how high up on the results list it appears) has as much to do with politics as it does with quality information. The search engine rankings are determined by a number of factors including the amount of information on the site, the amount of other sites that link to it, the number of people who select that link when searching, the length of time that the site has been listed in the search engine database, and the code of the site.

Recently, search engines such as Google and Yahoo have also been providing "sponsored links"—links that appear on the first few pages of the search results and that are paid for by advertisers. This means that you may end up clicking on something that is not relevant to your search, but instead actually advertising. The image presented here gives you an example of this on Google.

Example of paid advertising links at Google.

What does this mean for a researcher? Understanding the nature of the Internet, how to navigate it, and how it is organized can help you assess the quality of information and websites, filtering out that which does not relate or is of questionable quality.

3、Kinds of Search Engines and Directories

Web directories

Web directories (also known as indexes, Web indexes or catalogues) are broken down into categories and subcategories and are good for broad searches of established sites. For example, if you are looking for information on the environment but are not sure how to phrase a potential topic on holes in the ozone, you could try browsing through the Open Directory Project's categories. In its "Science" category, there is a subcategory of "Environment" that has over twenty subcategories listed. One of those subcategories is "Global Change" and this includes the "Ozone Layer" category. The "Ozone Layer" category has over twenty-five references, including a FAQ site. Those references can help you determine the key terms to use for a more focused search.

Search engines

Search engines ask for keywords or phrases and then search the Web for results. Some search engines look only through page titles and headers. Others look through documents, using Google, which can search PDFs. Many search engines now include some directory categories as well (such as Yahoo).

Metasearch engines

These (e.g., Dogpile , Mamma , and Metacrawler ) search other search engines and often search smaller, less well-known search engines and specialized sites. These search engines are good for doing large, sweeping searches of what information is out there.

A few negatives are associated with metasearch engines. First, most metasearch engines will only let you search basic terms, so there are no Boolean operators or advanced search options. Second, many metasearch engines pull from pay-per-click advertisers, so the results you get may primarily be paid advertising and not the most valid results on the Web.

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