A gateway is like a bridge, right?

Well, the concept of a bridge is not completely wrong.  "A gateway is a network that acts as an entrance to another network," therefore, acting like a bridge. (wiki)  One kind of gateway is that of library gateways which are created by specialists or librarians to support academic needs.  The other kind of gateway is that of subject specific databases also known as vortals.  Such databases are about a specific subject and are created by subject specialists or organizations. Gateways and subject specific databases assist searchers in locating resources that are in the "invisible web." Resources located in the invisible web are inaccessible through regular search engines because they require pass words, include documents behind firewalls, archived material, and other obstacles.  In order to access such material, one needs to find direct links to such documents or websites.  Use library gateways when looking for accurate academic content and subject specific databases when searching for direct links to specific topics. Examples of such networks are: Academic Information (Library Gateway) and Expedia (Travel, Subject Specific DB).

I had no idea about such bridges!  I have experienced problems when searching for specific pdf files online because many are blocked off.  However, if I search with specific criteria and point directly to the link I can get through! Beneficial information for the future. Previously, I was not familiar with any library gateways but I was familiar with some subject specific databases even though I was not aware of it.  I usually search for hotels or travel packages through expedia and I find it so much better than using an entire search engine with thousands of responses about "cruises" or "Boston."  A question I asked after reading about subject specific databases was, "How do they differ from subject directories?" As I visited each kind, I quickly noticed that subject specific databases are like search engines for one specific subject only such as travel, educational references, computer software, etc.  A subject directory is just that, a directory to various subjects.  A directory usually consists of various subject categories and subcategories.  For example, on a directory you may find "Health" as a category and then "health and fitness" and  "food and diet" as sub categories. Through re-reading the Bare Bones Tutorials, I am coming to understand the differences and similarities in search engines, subject directories, and subject specific databases.  Aside from noticing the differences, I am coming to appreciate their uses and the benefits of having access to such technological tools.