NCSA Mosaic for X 2.0 available

Marc Andreessen (
Wed, 10 Nov 93 00:24:12 -0800

Ladies and gentlemen, start your engines...

NCSA Mosaic for X 2.0 is now available. in /Mosaic:

o Source in /Mosaic/Mosaic-source.

o Binaries for SunOS 4.1.3, Solaris (yup) 2.3, AIX 3.2, IRIX 4.x,
DEC Alpha (OSF/1), DEC Ultrix, and HP/UX 9.x (700-series) in

Thanks MUCH to all the prerelease testers who sent us feedback and bug
reports -- your help made 2.0 into a vastly better product than it
would otherwise have been and will no doubt continue to improve Mosaic
throughout 2.x's lifespan.

If you have any comments, questions, or problems with Mosaic 2.0,
please send mail to Also please drop us a
note if you enjoy using Mosaic or if you are using it in any
interesting projects or applications -- we love to hear from our

The remainder of this message is a text copy of 2.0's "Help on
Version" and summarizes important changes and new features in 2.0.

The online version of this document is:

Introduction to NCSA Mosaic for X 2.0

This document is intended to serve as an introduction to NCSA Mosaic for
the X Window System version 2.0. It covers new features in version 2.0, and
changes from version 1.2, that will affect most users of Mosaic.

For more information on any of the details in this document, please feel free
to send mail to (or, alternately, to the World
Wide Web mailing list or the Usenet newsgroup

Status Of Documentation For 2.0

We are currently writing real Mosaic 2.0 documentation; it isn't yet
available, for which we apologize. In the meantime, this document should at
least help current users of Mosaic 1.2 upgrade to 2.0 without too much pain.

Potential Problems

This section is an up-front listing of how Mosaic 2.0 is different than
Mosaic 1.2 in ways that may cause apparent trouble to existing 1.2 users.

o The Mosaic executable has been renamed Mosaic, and the new class
name for Mosaic is, predictably, Mosaic. Existing Mosaic 1.2 X
resources and application defaults files should be modified to match.

o The method by which you customize the viewers Mosaic uses for
various datatypes (e.g. MPEG movies or PostScript documents) has
completely changed.

First, the multimedia X resources (e.g. gifViewerCommand) used
by Mosaic 1.2 are totally ignored by Mosaic 2.0. (Trust me, this is
really a good thing.)

Second, you now have complete control over the types of data
Mosaic can understand and what it does with each type, as well as the
file extensions that correspond to each type (when communicating
with a HTTP0 or FTP server).

Third, Mosaic now uses the MIME typing mechanism for naming
data types (e.g., the MIME type for a GIF image is image/gif).
This provides a substantial amount of interoperability with the
present and future of multimedia email on the Internet, but will
require a little readjustment on the part of users who are used to
simply calling GIF files "type GIF", etc.

For more information on these issues, see:

o Information on mapping MIME types to external viewers.
o Information on mapping file extensions to MIME types.

o Mosaic 2.0 speaks the HTTP/1.0 protocol, while Mosaic 1.2 spoke
the pre-HTTP/1.0 protocol commonly referred to as "HTTP0" or

This means that Mosaic 2.0 sends more complex queries to HTTP
servers than Mosaic 1.2 did. If you are running a fairly recent HTTP0
server (e.g. NCSA httpd 0.5), this should not be a problem -- the new
protocol is backward compatible, and Mosaic will go to great lengths
to make sure it interacts with the HTTP0 server correctly.

However, some old HTTP servers (anything pre-1993) will break
completely when sent a HTTP/1.0 query, and Mosaic 2.0 won't be
able to make things work. Such servers are actually in violation of
the final HTTP0 protocol specification and should at least be
upgraded to conform to that specification, if not HTTP/1.0.

o HTTP/1.0 servers are by now (November 1993) fairly widespread,
and many sites are using them without even realizing that they are
HTTP/1.0 servers, because they also talk HTTP0 to clients (like
Mosaic 1.2) that only talk HTTP0.

It is important to realize that HTTP/1.0 mandates server-side typing
of files. This means that the server must recognize, for example, that
the file extension ".gif" means that the file is a GIF image (i.e.,
MIME type image/gif), and must communicate this information
to the client within the HTTP/1.0 retrieval process. HTTP/1.0 clients
like Mosaic 2.0 will not look at file extensions to determine file types
when talking to HTTP/1.0 servers -- if the server gets the type
wrong, the client will not look at the suffix to try to figure out the
right type.

This means that if all of a sudden a file that Mosaic 1.2 always
handled as an HTML document is handled by Mosaic 2.0 as if it is a
binary data file, and the file is being served off an HTTP/1.0 server,
the server is (almost surely) at fault for not informing the client of
the correct type.

Related issue: Transparent uncompression is currently never done
when talking to a HTTP/1.0 server. This will be fixed in a
maintenance release. We do however discourage reliance on
transparent uncompression in general, as clients on other platforms
(e.g. NCSA Mosaic for the Mac & Windows) generally can't
uncompress files compressed using the standard Unix methods (
compress and gzip).

(Note to the skeptical: server-side typing is actually a powerful
feature of HTTP/1.0, despite any migration problems it may cause.
Also note that Mosaic 2.0 will still do file extension typing when
talking to HTTP0 servers, so you can always continue to run a
HTTP0 server in conjunction with Mosaic 2.0 if you prefer
client-side typing.)

o Mosaic 2.0 does not have the hardcoded Documents and Manuals
menus that were in Mosaic 1.2. They were removed for a number of
reasons too boring to go into here. If, however, you find yourself
"lost in cyberspace" because of the loss of those hardcoded menus,
choose the "Internet Starting Points" entry in Mosaic 2.0's
Navigate menu -- Mosaic will fetch a document from NCSA that
contains the contents of Mosaic 1.2's hardcoded menus in HTML

Also see the new "Internet Resources Meta-Index", also under
Mosaic 2.0's Navigate menu, for an alternate set of Internet
starting points perhaps more suitable to the task of locating any
specific piece of information on the network.

New Features In Mosaic 2.0

OK, this is the fun part. What will Mosaic 2.0 do for you?

o Completely interruptible I/O. At any point in a data transfer process
(hostname lookups and certain stages of direct WAIS queries
excepted), you can click on the icon in the upper right corner of the
window to stop the current network action.

o Fill-out forms. As per the current HTML+ spec, documents can
specify interactive fill-out forms -- with input elements including
text entry areas, toggle buttons, selection lists, popup menus, etc. --
and Mosaic will instantiate such fill-out forms as sets of Motif
widgets embedded inside the documents.

This provides a way to provide arbitrarily sophisticated front-end
interfaces to databases and search engines, as well as other network
services -- e.g., ordering pizzas.

See details on fill-out forms.

o Authentication. Thanks to Ari Luotonen at CERN, Mosaic can now
communicate properly with HTTP/1.0 servers that demand user
authentication before accessing information -- the user is presented
with an opportunity to enter a username and password to authenticate
herself to the remote server.

Currently, the "BASIC" authentication scheme is supported, which
provides for encoded (not cleartext, but not encrypted) transmission
of password data across the network. This provides a level of security
at least as secure as, e.g., telnet.

Once a user is authenticated on a particular server, Mosaic is smart
about caching and reusing the authentication information in
subsequent transactions with the same server in the same session --
the user will be informed at any time the cached authentication fails
and will be provided with the opportunity to enter a new username
and password again.

See the CERN authentication overview for more information.

o Direct WAIS access. Mosaic can now talk directly to WAIS servers
without needing to go through an intermediate gateway. This also

o Mosaic can cleanly retrieve and properly handle binary data
(images, audio, video, etc.) as well as HTML documents from
WAIS servers. Mosaic 2.0's normal customization
mechanisms can be used to customize what happens when
various types of binary data are accessed from WAIS servers.
o Mosaic natively supports freeWAIS's ability to tie together
multiple data files with different formats under a single
umbrella (e.g. as a result of a query across text, the user may
be presented with her choice of text, image, or audio).

Examples of direct WAIS access:

o Direct access to CNIDR WAIS directory of servers.
o Direct access to InterNIC RFC WAIS server.
o A search on the term "MIME" in the InterNIC RFC WAIS
o RFC 1437 from the InterNIC RFC WAIS server.

o Full format/viewer/extension customizability, including the ability
to allow local shell scripts to be launched from hyperlinks.

For more information, see:

o Information on mapping MIME types to external viewers.
o Information on mapping file extensions to MIME types.
o Information on allowing shell scripts to be executed via

o Native viewing of HDF and netCDF scientific data files. Here are
some examples:

o An HDF file of a galactic jet.
o A complex HDF file containing lots of different data
elements, including hyperlinks within annotations.
o A netCDF file.
o An image of NCSA Director Larry Smarr.
o A huge (5+ megabytes) HDF file of satellite weather image
and associated metadata.

Note: since it is possible for Mosaic 2.0 to be compiled without
native HDF/netCDF viewing support, your particular copy may not
be able to view the above examples.

o URL redirection. This means that a server can return, instead of a
document, a pointer to a document anywhere on the Internet. When
this happens, Mosaic will transparently attempt to fetch the new

Among other things, this enables clean graphical distributed
information space mapping -- a single image map can have hotspots
corresponding to information resources scattered throughout various
information servers across the Internet, and the user can jump to any
of those resources with a single mouse click.

For an example of URL redirection in conjunction with image
mapping, see the experimental Internet Resources Metamap.

o Inlined image caching, including customizability of the amount of
memory Mosaic will use to cache inlined images (default is 2048

Use the command line flag -ics or the X resource
imageCacheSize to set the size of the image cache in kilobytes.

o Delayed image loading, for users with slow network connections.
Use the -dil command line option or set the delayImageLoads
X resource to True to enable delayed image loading by default; it can
be controlled on a per-window basis from Mosaic's Options

o HTTP/1.0 support. In addition to enabling things like fill-out forms
support, redirection, and authentication, this means that Mosaic can
talk with the new breed of sophisticated HTTP/1.0 servers being
deployed on the network to the fullest extent of their -- and
Mosaic's -- ability.

See also the CERN HTTP/1.0 spec.

o Better hypermedia document display capabilities:

o Documents can be arbitrarily long now.
o Normal document text is formatted to the width of the visible
window, not the width of the widest element (e.g. sections of
preformatted text) in the document.
o Support for <BR> (line break) and <HR> (horizontal rule)
o Sophisticated support for inlining Motif widgets into
documents, which enables the fill-out forms support
described above.
o Performance speedups.

o URL canonicalization -- a fancy way of saying that Mosaic strips
redundant or useless information (like capital letters in hostnames,
":80" in HTTP queries and ":70" in Gopher queries, and trailing dots
in hostnames) out of all URLs it accesses. This makes the global
history tracking much more consistent by improving the odds that
two slightly different URLs that point to the same document are
recognized as identical by Mosaic.

o Improved system resource management -- many memory and socket
leaks were fixed. Due to these fixes and the inlined image caching
mentioned above, Mosaic should not be terribly hard on your system
even if you use it for a long time now.

o Better PostScript output, including output of color inlined images.

o Cute little icons in Gopher and FTP interfaces.

o Enhanced remote control features, including ability to scroll through
documents from shell scripts and cleanly fire off external viewers
(e.g. images and audio).

o Mouse tracking -- see the URL for the hyperlink under the pointer.

o Menu item File->Refresh Current provides a convenient
way to restore proper inlined image colors in a given window if the
colors have been previously stolen for another window's inlined
images -- keyboard accelerator (with pointer inside the scrolled
document viewing window) is Capital-R.

o Configurable Documents menu, for local site configuration.

o Full compile-time customizability of home page, docs directory, and
all other hardcoded URLs for sites without direct Internet access.

o Lots and lots of bug fixes and minor functionality and performance

More Information

You may wish to look over an exhaustive list of technical changes that took
place during the development of Mosaic version 2.0.

To take full advantage of Mosaic 2.0's capabilities, you should run a very
smart HTTP/1.0 server. We recommend NCSA httpd. If you prefer a
Perl-based server, try Plexus. Other options are CERN httpd and GN.

Marc & Eric

Marc Andreessen & Eric Bina
Software Development Group
National Center for Supercomputing Applications &