A World-Wide Web Workshop

John Louie, 5 May 1995

This guide presents some fundamentals on the Internet and the World-Wide Web information services, and allows you to design your own presentation on the Internet.

If you are a member of the Seismological Lab, you can most easily complete the exercises here in the Sun workstation lab, LME 320. Even if you are not affiliated with UNR, all the files we use are available via anonymous ftp from quake.seismo.unr.edu (134.197.33.40) in the vis/www directory. You need a WWW viewer and a text editor for the exercises. See the section below on Accessing the Internet for more information.

If you are completing this workshop on a Seismology Macintosh, you will find the following programs under the commands (Apple) menu: ``Netscape'', the WWW viewer; and ``BBEdit'', a text editor. There will be some variations from the instructions below.

Topics

Click on a topic to go directly to it.

Accessing the Internet

 If you are not affiliated with the UNR Seismological Laboratory or the Mackay School of Mines, you can most easily gain access to the Internet by contacting a commercial access providers. This is not a complete list: You will need a reasonably late-model computer with a color display, 8 or more megabytes of RAM, a fast modem, and a telephone line. The commercial access providers above can supply you with the software necessary to connect to the Internet, configured for their facilities. You can also purchase one of the many ``Internet Membership Kits'' or other books on the Internet (including software) at any bookstore or computer store.

If you are affiliated with the Lab and need a computer account, contact our System Administrator by sending email to sysadmin@seismo.unr.edu, or call the Lab at (702) 784-4975. If you are affiliated with the University, you can apply electronically for a UNR email account at http://www.unr.edu/new.html (you can use public-access computers in Getchell Library or Jot Travis Student Union to do this). Once you have a Seismological Lab account, proceed with the steps below:

1) Sit down at one of the Sun workstations in the Sun lab. Divide into small groups if there are more people than machines. Log in. Remember that, to type in a window, you will have to point the mouse at it and click the left button. To bring a window to the front, click on its header or title bar with the left mouse button (click left). Bring up a command input window from the background menu.

2) Start the Netscape World-Wide Web viewer application. In the command tool window, type the ``netscape &'' command. Once the viewer appears, click left on its ``Open'' button. In the dialog box that appears, enter ``http://www.seismo.unr.edu/ftp/vis/www/exercise.html'' and click ``Open''. Now you should be looking at this exercise.

Note that both the Mosaic and Netscape applications, running on the Suns, are a bit different from the usual Sun OpenWindows application in how they work with the 3-button mouse. You click the left mouse button to activate buttons, and you also hold it down to see the items in menus. Dragging the left button also selects text. Use the ``Edit'' menu items to copy and paste text.

The Internet

The Internet is known as a network of networks. This is true, but it doesn't explain how the Internet works, or what it can do for you.

Many people think of the Net in the same way as they think of a serial line, or a modem connection. You call up your service provider, establish a connection, log in to their computer, and then use their interface software to talk to other people, send mail, or download a file.

The Internet is much more than a serial cable connecting two computers. It is better to think of it as a bus, the kind you find inside a computer. A computer's bus connects many different devices, like CPU boards, disk drives, tape drives, video boards, and modem boards. Most devices like disk drives, video accelerators, and modem boards actually have their own internal processor chips, memory, and software. Each board on the bus has an address, too. The bus carries packets of information between boards, which communicate using some kind of protocol. Each packet carries a request, or perhaps some data in response to a request, that might ask the disk drive's processor to read a file, or carrying the data from that file. Packets can have particular origination and destination addresses, and other packets carry broadcasts that all the boards on the bus might want to pick up.

Now imagine a huge bus that connects hundreds, or thousands, of boards, with each board being a separate computer or workstation. Sitting at one computer, you can send requests to any of the other computers to take some action for you, and you can also hear any general broadcasts. In addition, other computers may send requests to yours, which it may or may not act on. Most of the packets flying by on the bus are not addressed to your computer, but are on their way somewhere else. When your computer sends a packet, it has to wait for the bus to quiet down, to get a word in edgewise. This is a more accurate picture of the Internet.

Given that you have a connection to the Internet, what you can do with it depends entirely on what types of protocols you are equipped to send, and respond to. The actual hardware carrying the Net bus signal may be microwave dishes, coaxial cable, or telephone wire. There may be packets encoded with AppleTalk, Novell, DecNet, or TCP/IP type protocols traversing these links. You may be familiar with some of the programs that use TCP/IP protocols, which are the most common. These include telnet, ftp, talk, finger, gopher, mail, news, and many others. Each of these protocols was designed to accomplish a different task: telnet establishes a terminal session; ftp can put or get files; finger queries for user information; gopher serves up menus of information; mail sends and receives messages; and news reads USENET news articles and posts responses. New protocols appear all the time.

Not only do you have to have a program on your computer that understands one of these protocols to use it, there has to be a server or daemon program running on some other machine that can respond to the protocol. And the server has to be set up so that it is willing to answer your request. This is a security issue, since every time you send mail, execute finger, or use any of the protocols, you are actually causing another computer to run a program for you.

The World-Wide WEB

The World-Wide WEB (WWW) is essentially just another set of TCP/IP protocols. Computers running HTTP daemon programs serve up data; and other computers running applications like Mosaic or Netscape use the http protocol to query the servers and view the data. Both server and viewer programs can run on almost any Macintosh, Windows PC, or UNIX workstation.

Two factors explain the new popularity of the World-Wide WEB. The first is the graphical nature of the WWW viewer programs. You can look at text, images, and movies, and hear sound all in one presentation, using only one program. And the interface provides hot hypertext links, so you can just click on a highlighted word, and the interface will take you to a new location. No more having to remember, and type correctly, such commands as ``ftp scec.gps.caltech.edu''.

The other factor is that most WWW viewer application programs, like Mosaic and Netscape, understand a whole host of TCP/IP protocols. When you specify the Universal Resource Locator (URL) that you want to see, you can specify a protocol as well as the address of the machine to run your request on. For instance, you can use the ``Open'' button to type a URL like

http://www.seismo.unr.edu/
This says that you want to ask the http protocol server program running on the machine at the address www.seismo.unr.edu for its default page. (Click above to find out what that is.) Or consider:
ftp://quake.seismo.unr.edu
This will ask quake.seismo.unr.edu to serve up the contents of its ftp directory, using that protocol. Your WWW viewer program takes care of the anonymous ftp login process automatically.

Now try

gopher://gopher.scs.unr.edu
Now your WWW viewer is acting as a gopher client too.

Also try:

news:comp.sys.sun
and
mailto:louie@seismo.unr.edu
Thus you can use your one WWW viewer application to access many types of Internet services.

In addition, you can use the URL format to open a file on your computer's local disk. If you know you have a folder on the local disk with a path name of, say, /tmp/myfolder , then try

file:///tmp/myfolder/
On a UNIX workstation you should find home directories at
file:///home/
On a Mac you could try
file:///Macintosh HD/System Folder/
On a PC try
file:///windows/system/
Once you get to a location on the disk, you can click on folders to navigate to them.

Here's one more trick. Try

telnet://neon.unr.edu
You can invoke a terminal session from your WWW viewer.

An Internet Treasure Hunt

Its easy to get lost among all the thousands of http servers out there, and the many pages each of them contains. The best strategy is to set out with a very specific objective in mind. Then you can navigate from server to server looking just for that one thing, and not get lost following every link. An objective also helps in searching various databases for places to go.

To help you, here are some places to start:

J. Louie's lists of sites

The Yahoo Index

The Internet Directory from Netscape Communications

UNLV's Internet Exploration Center

HotBot and Lycos, which are search engines.

Now for some objectives. See if you can answer the questions below. Be careful about downloading large datasets, images, or movies. All I want is for you to know where you can get things. After you find something interesting, don't forget to add it to your hotlist (in Mosaic) or your bookmarks (in Netscape).

First, if you are connected though the Seismology Suns, you'll look on your own computer:
What is in the .cshrc file in your home directory on the Sun?
How many maps of Africa are in the Sun directory /data/mapdata ?

Now lets find some resources on the Seismology Web server:
What protocol do you use to get a list of the most recent earthquakes?
What is Dr. Anderson's phone number?
How recent of an earthquake catalog is available by ftp?
How many lines of HTML source code describe J. Louie's home page?

Look around the University System:
What is Joe Crowley's phone number?
Find a picture of the Planetarium.
Anyone you know teaching at TMCC?

Now for some real Internet surfing:
Find an art museum or gallery.
Where do you download USGS 1-degree digital elevation maps? for Reno?
How many Sprites are in the Coke machine at CMU right now?
Do you need chains to drive Interstate 80 to Sacramento? What about Calif. State Route 2?
How's the snow at Boreal?
Where is an image showing how cloudy it currently is in Seattle?
What is the subject of today's Dibert comic strip?
Where does DOE have Yucca Mtn. publications on-line?
Listen to Clinton's message from the White House. Did you sign the guest book?
Download an on-line form 1040 from the IRS.
Where can you get the Acrobat Reader software by Adobe Systems?
Find Adobe's questions and answers on PostScript.
Where are some pages on scientific visualization?
Where can you get an image of Shoemaker-Levy impacts on Jupiter?
Find a movie fly-by of a volcano on Venus.
Who has a movie of wind-tunnel visualizations?
Find the Army's demonstration of geographic visualizations made with the GRASS program.

Building Your Internet ``Home Page''

You too can be an information provider on the Internet. First you need a server computer connected to the Internet, which the Seismological Lab will provide to staff, students, and those taking classes. Next you need to place your information into certain formats of data files, within folders on the Internet server. For a list of software available at the UNRSL for home page development, and pointers on their use, click here. The following file types are the most general:

Written Text: You can include commands from the HyperText Markup Language (HTML) in your text that will enable WWW viewer programs to see it with clickable hot links, in-line graphics, and even movies and sounds. Put an ``.html'' extension on the file names of your HTML text files.

Graphics: At present most WWW viewers can put two types of graphic formats in-line: the CompuServe Graphic Interchange Format, or ``GIF''; and the Joint Photographic Experts Group, or ``JPEG''. Both file typess are compressed images, and you can read about a variety of tools we have available for converting PostScript plots and other image formats to GIF and JPEG format. Put a ``.gif'' or ``.jpg'' extension on the file names of your images.

Multimedia: For sounds, use the ``.au'' or ``.wav'' formats, for movies, use ``.mpeg'' or ``.mov'' (Apple QuickTime) for maximum compatibility.

The file name extensions are important because they clue your WWW viewer program into what ``helper applications'' to start, which actually handle displaying additional graphic formats, and play sounds and movies. To take full advantage of a wide variety of helper applications, it's important to include each helper application in the list under the ``Options->General Preferences->Helper Applications...'' menu items in your WWW viewer (or in the file that option window refers to). Most 1996 and later viewers come with the ability to interpret the HTML, JPEG, MOV, and GIF formats without needing any helpers.

Writing Your Home Page in HTML

An HTML file is really just a plain ASCII text file, like a program listing or an e-mail message, with scattered formatting commands inserted. Programming HTML is not like editing a page in a ``what-you-see-is-what-you-get'' word-processing program; you edit the formatting in your simple text editor (like ``notepad'', ``wordpad'', ``textedit'', ``emacs'', or ``TeachText''), save the changes, and then see the result by opening the local file in your WWW viewer. If you see a mistake, you go back to the editor and try again.

One of the best features of the World-Wide Web is that it is very easy to see, and adopt, the HTML formatting code that anyone else uses to prepare their Web pages. Whenever you see a page you like, select the ``View->Source'' menu item, and you will get an editing window showing the original HTML formatting commands within the text. You can save the code to your own file, and change it to suit you.

For an example of a brief home page, go to John Louie's home page, view its HTML source, and save that as a file in your home directory.

The page above gives you an example of some of the information you might want to include in your own home page. You might want a title (to appear at the top of the WWW viewer window), some headings, paragraphs of text, in-line images, and links to other files and sites.

Note that the formatting commands are enclosed in ``<>'' angle brackets. By learning just a half-dozen different formatting commands, you can make a great variety of documents.

A title in HTML looks like:

<title>Document Title</title>

A heading looks like:

<h1>Section Heading</h1>

Here's a paragraph separator:

End of last paragraph.
<p>
Beginning of next paragraph.

This construction will insert an image into the text line, from a file named ``my-picture.gif'':

This <img src="my-picture.gif"> is a picture of me.
This works if the picture file is in the same folder on the server as the HTML file that references it. References to files in HTML formatting are usually relative; here's an example where the picture is in a ``photos'' sub-folder of the folder holding the HTML document that references it:
This <img src="photos/my-picture.gif"> is a picture of me.
All the usual UNIX path name specifiers work within such references: ``/'' separates folders from sub-folders; a path reference beginning with a ``/'' addresses the root of the server's file system (according to the protocol served); a ``..'' is the parent folder; and ``~user'' will sometimes address the home directory of the user with id ``user'' .

Now here is an example of an absolute reference, specifying a protocol, server, and path name as well as the picture's file name:

This <img src="ftp://quake.seismo.unr.edu/pub/louie/home/me.gif"> is a picture of J. Louie.

To make a hypertext link to another document, all you have to do is give a reference, in the style below, to another HTML document. The same considerations for relative and absolute path specifiers apply here too:

Click <a href="resume.html">here</a> to view my resume.
With this form, the word ``here'' will be underlined and linked; clicking on it will navigate to the resume document. Note that the WWW viewer knows it is a hypertext link because the link points to a file with an ``.html'' name extension.

By now you have probably added some interesting places to your hotlist or bookmarks. Your own home page can give links to them by adding lines like the one below, with absolute links:

D. Ring made a nice <a href="http://www.seismo.unr.edu/htdocs/info.html"> earthquake information page</a> for the UNR Seismo Lab.

HTML Programming Resources

 You can get a more thorough introduction to HTML programming by looking at A Primer on the HyperText Markup Language from NCSA. Look especially at the section on The Minimal HTML Document. Northwestern University also has a comprehensive list of helpful manuals in its Guide to HTML Authoring & Web Resources

Now create a simple home page for yourself, using J. Louie's as an example. Make sure it has a title, a heading, your name, some information about your academic or research interests, and a few links to other, interesting places. Name the HTML document home.html, put it in your home directory on the Sun, and put any other HTML and GIF files it references in your home directory also.

When everything is tested and ready, send e-mail to ``webmaster@seismo.unr.edu'', telling them the names of the files and that they're in your home directory, and asking them to install them on the Seismology WWW server and notify you of the URL. Click here to send email.

Aside from presenting your information correctly, it is often important to present yourself in an appropriate style. Check out the Guide to Web Style from Sun Microsystems.

Add a Graphic to Your Home Page

 For the class's lab we set up a way to put a picture of you, or any other object or display you please, into digital form for your home page.

A monochrome camera set up on one of the Macintoshes in LME 320 can take digital photos. It looks like a slightly oversized golf ball on a triangular base. In the Apple menu find the ``QuickPICT'' application and start it up. Preview your picture and snap it, saving it as a PICT file on the Desktop. Then find the ``Fetch'' application in the Apple menu, open a connection to quake using your login and password, and ``Put'' the file into your Sun home directory. Close the Fetch connection.

On the Sun, you can use a command like the following to open your picture:

xv3 picture.pict &
When you see the display window, click the right mouse button on it to get the control panel to pop up. Then you can press the Save button, and select the GIF format, thus converting the picture. You can drag on the picture with the middle mouse button and press Crop to select the best part of the picture. The ColEdit button makes it possible to change the image's contrast, brightness, etc. (Or convert it on the Mac with the GraphicConverter application before you transfer it to the Sun.)

If we should have a color video camera set up on a Sun, you will find appropriate instructions here.

Don't forget to ask the Seismo webmaster to install your home page and graphics! Click here to send email.

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