WHAT ARE SUBJECT DIRECTORIES?
Subject directories, unlike search engines, are created and maintained by human editors, not electronic spiders or robots. The editors review and select sites for inclusion in their directories on the basis of previously determined selection criteria. Directories tend to be smaller than search engine databases, typically indexing only the home page or top level pages of a site. They may include a search engine for searching their own directory (or the web, if a directory search yields unsatisfactory or no results.)
HOW DO SUBJECT DIRECTORIES WORK?
When you initiate a keyword search of a directory's contents, the directory attempts to match your keywords and phrases with those in its written descriptions. There are general directories, academic directories, commercial directories, portals and now, vortals. Portals are directories that have been created or taken over by commercial interests and then reconfigured to act as gateways to the web. These portal sites not only link to popular subject categories, they also offer additional services such as email, current news, stock quotes, travel information and maps. Vortals, or vertical portals are single, subject-specific directories.
Many search engines are acquiring subject directories or creating their own.
PROS:
Directory editors typically organize directories hierarchically into browsable subject categories and sub-categories. When you're clicking through several subject layers to get to an actual Web page, it may appear cumbersome, but it is also the directory's strength. Because people maintain subject directories, they have the capability of delivering a higher quality of content.
They may also provide fewer results out of context than search engines.
CONS:
Unlike search engines, most directories do not compile databases of their own. Instead of storing pages, they point to them. This situation sometimes creates problems because, once accepted for inclusion in a directory, the Web page could change content and the editors might not realize it. The directory might continue to point to a page that has been moved or that no longer exists.
Dead links are a real problem for subject directories.
WHEN DO YOU USE SUBJECT DIRECTORIES?
Like the yellow pages of a telephone book, subject directories are best for browsing and for searches of a more general nature. They are good sources for information on popular topics, organizations, commercial sites and products. When you'd like to see what kind of information is available on the Web in a particular field or area of interest, go to a directory and browse through the subject categories.
EXAMPLES OF SUBJECT DIRECTORIES AND PORTALS :
Subject Directories
Portals (subject directories serving as home pages)
Subject directories, unlike search engines, are created and maintained by human editors, not electronic spiders or robots. The editors review and select sites for inclusion in their directories on the basis of previously determined selection criteria. Directories tend to be smaller than search engine databases, typically indexing only the home page or top level pages of a site. They may include a search engine for searching their own directory (or the web, if a directory search yields unsatisfactory or no results.)
HOW DO SUBJECT DIRECTORIES WORK?
When you initiate a keyword search of a directory's contents, the directory attempts to match your keywords and phrases with those in its written descriptions. There are general directories, academic directories, commercial directories, portals and now, vortals. Portals are directories that have been created or taken over by commercial interests and then reconfigured to act as gateways to the web. These portal sites not only link to popular subject categories, they also offer additional services such as email, current news, stock quotes, travel information and maps. Vortals, or vertical portals are single, subject-specific directories.
Many search engines are acquiring subject directories or creating their own.
PROS:
Directory editors typically organize directories hierarchically into browsable subject categories and sub-categories. When you're clicking through several subject layers to get to an actual Web page, it may appear cumbersome, but it is also the directory's strength. Because people maintain subject directories, they have the capability of delivering a higher quality of content.
They may also provide fewer results out of context than search engines.
CONS:
Unlike search engines, most directories do not compile databases of their own. Instead of storing pages, they point to them. This situation sometimes creates problems because, once accepted for inclusion in a directory, the Web page could change content and the editors might not realize it. The directory might continue to point to a page that has been moved or that no longer exists.
Dead links are a real problem for subject directories.
WHEN DO YOU USE SUBJECT DIRECTORIES?
Like the yellow pages of a telephone book, subject directories are best for browsing and for searches of a more general nature. They are good sources for information on popular topics, organizations, commercial sites and products. When you'd like to see what kind of information is available on the Web in a particular field or area of interest, go to a directory and browse through the subject categories.
EXAMPLES OF SUBJECT DIRECTORIES AND PORTALS :
Subject Directories
Portals (subject directories serving as home pages)
WHAT ARE GATEWAYS AND SUBJECT-SPECIFIC DATABASES?
Gateways
There are two kinds of gateways: library gateways and portals. Library gateways are collections of databases and informational sites, arranged by subject, that have been assembled, reviewed and recommended by specialists, usually librarians. These gateway collections support research and reference needs by identifying and pointing to recommended, academically-oriented pages on the Web. See list of examples below.
Subject-Specific Databases (sometimes called "Vortals")
Subject-specific databases, or vortals (i.e., "vertical portals") are databases devoted to a single subject, created by professors, researchers, experts, governmental agencies, business interests, and other subject specialists and/or individuals who have a deep interest in, and professional knowledge of, a particular field and have accumulated information and data about it. See list of examples below.
WHAT IS THE "INVISIBLE WEB"?
There is a large portion of the Web that search engine spiders cannot, or may not, index. It has been dubbed the "Invisible Web" or the "Deep Web" and includes, among other things, pass-protected sites, documents behind firewalls, archived material, the contents of certain databases, and information that isn't static but assembled dynamically in response to specific queries.
Web profilers agree that the "Invisible Web," which is made up of thousands of such documents and databases, accounts for 60 to 80 percent of existing Web material. This is information you probably assumed you could access by using standard search engines, but that's not always the case. According to the Invisible Web Catalog, these resources may or may not be visible to search engine spiders, although today's search engines are getting better and better at finding and indexing the contents of "Invisible Web" pages.
In order to access so-called "Invisible Web" sites, you need to point your browser directly at them. That's what many library gateways and subject-specific databases do. They are good sources for direct links to database information stored on the "Invisible Web."
Gateways
There are two kinds of gateways: library gateways and portals. Library gateways are collections of databases and informational sites, arranged by subject, that have been assembled, reviewed and recommended by specialists, usually librarians. These gateway collections support research and reference needs by identifying and pointing to recommended, academically-oriented pages on the Web. See list of examples below.
Subject-Specific Databases (sometimes called "Vortals")
Subject-specific databases, or vortals (i.e., "vertical portals") are databases devoted to a single subject, created by professors, researchers, experts, governmental agencies, business interests, and other subject specialists and/or individuals who have a deep interest in, and professional knowledge of, a particular field and have accumulated information and data about it. See list of examples below.
WHAT IS THE "INVISIBLE WEB"?
There is a large portion of the Web that search engine spiders cannot, or may not, index. It has been dubbed the "Invisible Web" or the "Deep Web" and includes, among other things, pass-protected sites, documents behind firewalls, archived material, the contents of certain databases, and information that isn't static but assembled dynamically in response to specific queries.
Web profilers agree that the "Invisible Web," which is made up of thousands of such documents and databases, accounts for 60 to 80 percent of existing Web material. This is information you probably assumed you could access by using standard search engines, but that's not always the case. According to the Invisible Web Catalog, these resources may or may not be visible to search engine spiders, although today's search engines are getting better and better at finding and indexing the contents of "Invisible Web" pages.
In order to access so-called "Invisible Web" sites, you need to point your browser directly at them. That's what many library gateways and subject-specific databases do. They are good sources for direct links to database information stored on the "Invisible Web."
WHAT IS THE "INVISIBLE WEB"?
There is a large portion of the Web that search engine spiders cannot, or may not, index. It has been dubbed the "Invisible Web" or the "Deep Web" and includes, among other things, pass-protected sites, documents behind firewalls, archived material, the contents of certain databases, and information that isn't static but assembled dynamically in response to specific queries. Web profilers agree that the "Invisible Web," which is made up of thousands of such documents and databases, accounts for 90% of existing Web material. This is information you probably assumed you could access by using standard search engines, but that's not always the case. According to the Invisible Web Catalog, these resources may or may not be visible to search engine spiders, although today's search engines are getting better and better at finding and indexing the contents of "Invisible Web" pages. In order to access so-called "Invisible Web" sites, you need to point your browser directly at them. That's what many library gateways and subject-specific databases do. They are good sources for direct links to database information stored on the "Invisible Web." |
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WHEN DO YOU USE LIBRARY GATEWAYS AND SUBJECT-SPECIFIC DATABASES?
Use library gateways when you are looking for high quality information sites on the Web. You can be fairly certain that these sites have been reviewed and evaluated by subject specialists for their accuracy and content.
Use subject-specific databases when looking for information on a specific topic, e.g., news links, multimedia files, archives, mailing lists, people, job finders, and thousands of databases devoted to specific topics of interest. Today, more and more of the so-called "main-stream" search engines, subject directories and portals are pointing to these subject-specific databases, using direct links on their home pages.
EXAMPLES OF LIBRARY GATEWAYS
Use library gateways when you are looking for high quality information sites on the Web. You can be fairly certain that these sites have been reviewed and evaluated by subject specialists for their accuracy and content.
Use subject-specific databases when looking for information on a specific topic, e.g., news links, multimedia files, archives, mailing lists, people, job finders, and thousands of databases devoted to specific topics of interest. Today, more and more of the so-called "main-stream" search engines, subject directories and portals are pointing to these subject-specific databases, using direct links on their home pages.
EXAMPLES OF LIBRARY GATEWAYS
- Academic Information
- Digital Librarian
- Internet Public Library
- Librarians' Index to the Internet
- WWW Virtual Library
- Educator's Reference Desk (educational information)
- Expedia (travel)
- Internet Movie Database (movies)
- Red Book (car values)
- Seek (jobs)
- Motley Fool Australia(personal investment)
- Shopbot (comparison shopping)
- Roller Coaster Database (roller coasters)
- Voice of the Shuttle (humanities research)
- WebMD (health information)
Activity Time 3
Explore some vortals, gateways, portals and subject directories found in the search engines below.
Search Engines
Grouping Key: White = Kids search engines; Yellow = metadata search engines; Orange = General search engines; Red = Visual-relational search engines; Purple = Subject search engines; Pink = Australian search engines; Black = Dictionaries with a difference; Teal = Search help