Mosaic
Mosaic was developed at the National Center for Supercomputing
Applications (NCSA) as an Internet-based, global, hypermedia browser
which allows users to discover, retrieve, and display documents and
data from all over the Internet. Global hypermedia means information
located around the world is interconnected in an environment which
allows users to travel through the information by clicking on
hyperlinks (items in documents which point to other related files).
NCSA Mosaic can run on three platforms - X
Window System, Apple
Macintosh, and Microsoft
Windows. Information about all three versions is available online
through the Mosaic
entry page.
A series of documents are available through Mosaic which describe how
to navigate through the WWW. Separate documentation exists for each of
the three available Mosaic versions: X
Window System, Apple
Macintosh, and Microsoft
Windows. The following is a general description of the Mosaic
window that applies to all three versions.
Mosaic is based on the concept of hyperlinks. A hyperlink is
designated by underlined text linked to another document. Thus, to
view the attached document, single-click on the underlined text.
Mosaic also keeps a window history on every document viewed. Clicking
the Back button will travel back through the window history.
Likewise, clicking the Forward button will travel forward
through the window history.
Clicking on the Window History feature displays the list of
documents viewed. Double-clicking on any document title jumps to that
document. The first document on the list is the home page - the
document viewed when first entering Mosaic. Clicking on Home or
Home Document button jumps to this document.
To open a particular document for viewing, users can click on the
Open Local button if the document is located on your own server
or on the Open URL button if the document is located on another
server. If a document transfer is taking too long, users can abort by
clicking on the Mosaic icon in the upper right corner of the window.
Once a document is retrieved, it can be searched to find the
occurrence of a word or group of words. To search a document, click on
the Find or Search key and enter the phrase for which
you are searching.
A document can also be printed or saved. To print a document, click on
the Print key and enter the printer name and the format for the
file. To save a file, click the Save or Save As key and
enter the location for the saved file.
There are numerous options to choose from when Mosaic is started.
They include: colors of the Mosaic window; font types; location of
Mosaic files; system commands, and external viewers. These options
can be specified or they can take on their own default settings. To
find out information about setting these configuration variables for
each version of Mosaic, please see the documentation provided for the
X
Windows, Apple
Macintosh, and Microsoft
Windows systems.
Most people using Mosaic prefer to have a specialized home (entry)
page appear when they start Mosaic instead of viewing the default
home page. A home page is the page that appears when Mosaic is first
executed. By creating a HTML document containing the items which will
appear on their home page and including links to other files that
wished to be accessed, this can be accomplished. To learn the
particulars of how to do this, please see the revelant documentation
for the X
Windows, Apple
Macintosh, and Microsoft
Windows systems.
This document contains a number of terms which were only vaguely
explained. This section clarifies the definition of some of these
terms.
When Mosaic attempts to retrieve a document, it needs to know where to
look. Therefore, users must provide an "address" which tells the
computer the location of the file. This address can point to any file
in the world which resides on the Internet. It must include the
transfer protocol, the server's name where the file resides, the port
number, the path, and name of the file. This address is known as a URL (Uniform
Resource Locator).
The URL is constructed in the following format:
protocol://server:port/path/filename
Protocol can be either WAIS, network news, gopher, telnet, ftp,
whois, or
HTTP. Server is the server
which provides the document to the client. For example, the NIST
server which is available to the public is www.nist.gov.
Port is the network port number (default is 70 for gopher and
80 for HTTP). Path is the path where the file resides.
Filename is the name of the file to be retrieved.
A sample URL is NIST's Mosaic entry page:
http://www.nist.gov/welcome.html
The transfer protocol is HTTP, the server is www.nist.gov, the port
number is 80, there is no path specified, and the file name is
welcome.html.
An exception to this rule is when the user is accessing a local file.
In this case, only the path and the filename are needed. The URL for a
local file is constructed in either of the following formats:
file:/path/filename
/path/filename
This is the format on the SUN platform. The format for the PC
and MAC
platforms are slightly different.
In both cases file is the transfer protocol (either written or
implied), path is the path in which the file is located, and
filename is name of the file to be retrieved.
HTTP
(Hypertext Transfer Protocol) provides a fast, stateless,
information retrieval protocol when a large number of references
exists between many sources of networked information. This protocol
allows users to quickly follow links between sources which are located
anywhere on the Internet.
The protocol is stateless - a transaction consists of a connection
between a client and a server, a request by the client, a response by
the server, and the closing of the connection. The connection uses
port 80, by default.
HTML
(Hypertext Markup Language) is a language for creating plain text
documents which include hyperlinks to other files located anywhere on
the Internet. HTML is a Document Type Definition (DTD) of the Standard
Generalized Markup Language (SGML). SGML is a specification for DTD's
and HTML is a specialization of SGML.
Tags are used to tell clients how to represent text and are denoted
within angle brackets (<>). Tags can denote titles, headers,
paragraphs, lists, and preformatted text. Most tags must have an
ending tag to denote the end of specified text. The ending tag looks
just like the beginning tag except a slash (/) precedes text within
the angle bracket.
The advantage of HTML over other DTD's is its ability to link to other
documents. Any item in the document can be linked, including text and
images. This is done by using the <a href> tag. The format is as
follows:
<a href="URL">item</a>
where <a is the opening anchor, href= denotes what
document to link to, URL is the
URL of the document, > points
to the text which activates the link, item is the item in the
document which serves as the hyperlink, and </a> is the
ending anchor. The anchors are important because they denote where
hyperlinks occur.
There are many more features which HTML offers. To learn more, please
see the document "A Beginner's
Guide to HTML" or "HTML TUTORIAL"
located on the WWW.
There are a number of documents available to help further understand
the capabilities of Mosaic. Some include:
- Mosaic Demo Document
- an interactive hypermedia tour of Mosaic's capabilities
- What's New
- recent changes and additions to the universe of information
available to Mosaic and the WWW
- NIST's Homepage
- information about NIST - programs, partnerships, awards, and
laboratories
Most of these documents can be accessed through Mosaic's default home page.
You may also want to:
Last Edited: Tuesday, 23-Jul-1996 13:55:12 EDT
Written by: Craig Schlenoff