The format for an URL follows a straightforward hierarchy. First comes the type of service, or the Internet protocol to be used for successful communication. Second is the address of the server, which identifies the particular host computer you are requesting information from. In some cases the port number (communication channel that this host uses for that application) also goes here. This is vaguely analogous to a suite or apartment number. Last comes the location on the host of the document or application to be run to service a request for information.
A URL then looks like a somewhat long and convoluted path. Imagine addressing an
envelope and putting name, street number, town, state, and zip all on one line, separated by various
punctuation characters. Anyway, it looks like this:
ResourceType://Host.Domain:Port/DocumentLocation/DocumentName
One thing that must be remembered here is that document in this context is not limited to
text or data files. When using the World Wide Web (WWW)--a distributed hypermedia system that
resides in CyberSpace--a document can be an image, video, or sound file, as well as plain text, data,
or application files (executables.)
The most common format for text in the WWW though, is as a html document, which stands for HyperText Markup Language. Documents which have been put into html format can have embedded hypertext links which lead to other documents, as well as imbedded graphics and sound. These hyperlinks are URLs that point to a related resource, or more detailed information. This information expansion can take place on the same host, or one located on the other side of the globe. Using Mosaic, Lynx, or another hypertext client (commonly known as a Web Browser,) you can find everything from companies that produce a 3D Seismic Finite Difference Simulator with Recursive Grid Refinement and pulsed power energy guns (http://www.scubed.com:8001/products/Products.html) to the latest release from the Meat Puppets (http://www.mtv.com/puppets.au)
One of the advantages of URLs embedded into html documents is that their use can be completely transparent to the user. By accessing a html document, the hyperlinks are normally displayed as highlighted and/or underlined text that is either descriptive of the document or says something like, “neat document here.” Hyperlinks can also be graphic images such as buttons to be clicked on, but in neither case is the underlying URL apparent to the user. The browser just sends a request to the proper server for the information.
The use of URLs also makes it quite easy for others to check your references in hypertext documents published in CyberSpace :-) As simply as clicking a mouse button or pressing the Tab and Enter keys, an interested reader can get all the further detail they desire.
So point your browser to a starting point document (httpd://www.ncsa.uiuc.edu/SDG/Software/Mosaic/StartingPoints/NetWorkStartingPoints.html) or (http://www.einet.net/galaxy.html) and surf CyberSpace for an hour or two. See if you can find the research institute that specializes in energy and ecology issues, the Jupiter/comet pictures, or the Louver in Paris, France.
As a final note, if you would like to discuss anything in this column in further detail, or would like to make suggestions for topics for future columns, send e-mail to dave@past.com and we’ll make CyberSpace work for us.
|
|
|
|
|
|
|
|
|---|
Questions or comments about these Web pages? Send e-mail to
dave@reststop.net