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 Lesson Two: Where do I start? (Web Directories) What is a Web Directory?A web directory is a subject tree or subject directory, that is, a listing of subjects organized into categories, which are usually arranged hierarchically. For example, if you are looking for information on web graphics, the hierarchy might look something like this:Computers
which could also be represented as: each category may be a listing of sub-topics. Directories may be organized in a variety of ways such as topically or alphabetically and have many different formats (a relatively simple listing of phone numbers to a complex attempt to organize and classify large portions of the web into subjects and sub-categories). It is important to remember that no one has categorized the entire
web. There are millions of web pages on the web and it is simply impossible
to organize everything, especially at the rate the web is expanding. (In
the early days of the web, folks sometimes aspired or claimed to be working
towards documenting and classifying the whole web, but now most of us realize
that this is impossible). A directory is a collection or database of web
sites classified in a meaningful way.
What's the difference between a Directory and a Search Engine?Folks everywhere are confused about the differences between directories and search engines, in part because of the way in which we use them and their apparent similarities. A simple but definitive difference is:This simple premise makes a world of difference. Directories and search engines as we usually think of them, may be compared and contrasted in several areas:
How are sites selected to be included in the database? Directories: rely on the judgment and expertise of the people compiling them and it's not hard to see that subject experts would have different selection criteria than a hobbyist or casual user. Also, the process is governed by the whims of the folks looking at the sites -- today I might include it in the directory listing, but tomorrow I may not. Listings may be submitted to the directory for possible inclusion, or chosen by the indexer. Whether or not your site is included in the database is a function of how relevant it is to the subject matter of the directory, its scope, coverage, and accuracy, in additional to other selection criteria such as audience. Key issue: maintenance of established level of quality. Search Engines: also called intelligent agents, worms, crawlers, spiders and robots ('bots), are automated. They traverse the web site content and its links in a variety of different ways and collect the results into a database. Webmasters can also submit their sites for possible inclusion into the database. Additionally, the search engine itself seeks out the key words or phrases in web sites (or indexes each word) and includes the documents in which they occur into its database. (This is a very simplistic description of how a search engine works!) So frequently it is only a matter of time before your new site gets indexed by one of the major search engines. Key issue: indexing web documents for maximum
access (not quality driven).
Access How do I access the information I need? Directories: Because of their hierarchical arrangement, most directories are browsable, that is, you can click on a subject of interest to see pertinent links and subcategories on your topic. You are dependent upon the indexers vocabulary to describe your topic, and you may have to figure out exactly what that is (for example, you may want information on cars, only there isn't a category for "cars" but there is one for "automobiles."). Although this may be slightly confusing at first, by using controlled vocabulary -- that is, one subject heading to describe topics (such as cars, automobiles) instead of several, you'll find all the information on the subject in one place. Some of the larger directories allow you to search for topics, but it is very important to remember that this is a limited kind of search -- you are searching for subject categories within the directory and its database, not in actual web documents. Key issue: accurately classifying web sites (usually into subject areas) Search engines: You search the database of a search engine by entering a key words into a dialog box; web sites in which these terms occur are presented as relevant documents. Almost everyone has had the experience where you go to a web site that is high in the rankings, only to find out it is completely off topic! In Lesson One, we looked at many of the reasons this happens. Key issue: relevant retrieval by using automated indexing techniques Special: It is important to note, that because someone, rather than something compiles the directory databases, most of the web sites classified in a topic area are really about your topic. Usage When would I use a directory? a search engine? Directories: Use a directory when you want to see what is available on a topic, when you are beginning your research or when you trust the compiler of the directory to channel you to the best sites. Key issue: Well organized directories save time with preliminary research Search engines: Use a search engine when time is not a factor (to sift through many sites), when you know what most of the directories are listing but you'd like to see new sites, or those that may not have been included into major directories. Also use search engines to continue your research -- remember, if a site or page is not entirely devoted to a topic, it may not be included in a directory and so querying a search engine by key word may be the only way it is accessible. Key issue: because they index words and images within a web document, search engines are powerful tools for finding information not considered by a human to be the main "topic" of a web page Kinds of DirectoriesIf we use the definition that a directory is any listing of links compiled by someone (as opposed to an intelligent agent), then almost any listing of links organized in some fashion could qualify. In practical terms, however, when folks are discussing web directories, they are usually referring to sites attempting to organize a very large amount of information, or sites that specialize in a limited subject area.Apart from differing in subject area, directories now are attempting to distinguish themselves by the type of "value" they add to an otherwise unexciting listing of sites -- for example, annotations, ratings, and rankings. Also, most of the major search engines now also have directory listings as a service. And don't overlook your local libraries, colleges and universities when looking for web "directory assistance" either! Directories:Argus Clearinghouse (http://www.clearinghouse.net)
Assignments:Describe two of the directories below in regard to the following criteria:
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