Concepts which xmosaic uses

Mosaic is based on the concept of hyperlinks. Typically, a hyperlink is of a blueish colour and may be underlined. When the user clicks on the hyperlink (in the Mosaic language, it is called an "anchor") using the mouse, the link is followed to wherever it is pointing.

It may be to another document at another site, or a plain ASCII file. In the latter case, it would be displayed.

If the hyperlink points to a PostScript file, a PostScript viewer on the local system is spawned and the PostScript file is viewed. Typically, "ghostview" is used for PostScirpt files, "xv" is used for ".gif" files.

URL - Uniform Resource Locator: a string describing the type of resource to fetch and where the resource is.

HTML - HyperText Markup Language: language to write Mosaic documents. Contains directives to access a URL.

Types of URL's:

ftp: allows automatic connection to an anomymous FTP site. Through Mosaic, allows directory navigation and file retrievals. Depending on the file type, a different program will be called to view the content of the file:

File Type Program Used --- ---- PostScript ghostview .fig xv .dvi xdvi ASCII will be displayed in Mosaic window.

Any file can be automatically downloaded to a local file with the click of a mouse button.

ex: ftp://anonymous:www-entry@nrcnet0/pub/unixug/

http: hypertext transport protocol: connect to a Mosaic server, using a specific html document.

ex: http://www.sao.nrc.ca/home.page.html

2.1.5.3. gopher: connect to a gopher server.

ex: gopher://gopher.tc.umn.edu

2.1.5.4. telnet: open a telnet session. "xterm" will be used as a window.

ex: telnet://nickel.sao.nrc.ca

2.1.5.5. file: gives access to a specific file. The file must be in an anonymous FTP account.

ex: file://nrcnet0.nrc.ca/welcome.msg

2.1.5.6. news: to read USENET newsgroups. Unfortunately, I couldn't get it to work on our News Server (variable NNTPSERVER must be set).

ex: news://comp.sys.sgi/

Tips and tricks on accessing WWW sites, that would also apply if one writes HTML files for others to access:

• When documents are read with lynx or with graphics turned off, information normally given by the images is lost. That information should be available using text (HTML has the constructs to do that; unfortunately too many people don't use them.
• Large (or many) pictures use up a lot of bandwidth. As a result, it takes a long time to display the document.

  A good balance between graphics and text should be maintained.

• The rotating "world" cold be clicked to stop a file transfer.
• There are converters available do translate from WordPerfect or to HTML.

  In fact, these course notes are available on

  http://www.sao.nrc.ca

  in HTML (the source is in ).
• If possible always test the new documents with several systems (PC, MAC, UNIX colour, UNIX b&, X terminals) to ensure that it is readable from all.

  If the document is being read and looks shabby, it may be because it was written using a different platform than you are using...

• Try to access a local home page document. The NCSA Mosaic site (the default one) is overwhelmed by requests.

  Most of the SGI Science Institute servers in Ottawa access the SAO/SCSG home page listed above.

  Any user may write their own home page and access it using

  xmosaic you_home_page

  If the server you are using is running an http server, you can make you own documents availabe by anyone with a brower by putting your document in directory

  $HOME/public_html/document.html

  where document.html is the document you would like to serve.

  People could then accessing you file by accessing URL

  http://server_name/elogin/document.html

  where server_name is the name of the system, login is your logon account, and document.html is to document opened to the public.