An Alpha release of version 5.2 of the Prospero file system is now
available by anonymous FTP from PROSPERO.ISI.EDU in the file
pub/prospero/prospero-alpha.5.2.tar.Z.  It can also be obtained
through Prospero itself from /releases/prospero/prospero-alpha.5.2.tar.Z.  
The name prospero.tar.Z in those directories still points to the stable
Beta 5.1 release; this has been done for the sake of the archie server
maintainers and other information providers who depend upon Prospero. 

Some important changes since the last Prospero release should be of
interest to the readers of comp.infosystems.gopher:

(a) A menu-based browser client, similar to the Gopher client
(b) A gateway server which makes all of Gopherspace available through 
    Prospero queries. 
(c) A menu-based browser API interface library to Prospero, which allows
    one to easily write new browsers that use Prospero to make their underlying
    calls.

The menu-based browser supports all of the basic Gopher types:
searches, text files, data files, and portals (what Gopher calls
telnet sessions).  It does not yet support sophisticated display of
binary image files, reading Postscript or MIME documents, playing
sounds, or automatic decoding of uuencoded, compressed, or tarred
files.  These enhancements will be added shortly; the protocol
definitions for them have already been made.

We support authenticated remote modifications to menus, though not
presently from within the browser itself.  For now you will have to
learn how to use a few Prospero commands to add new menus or items and
set descriptions.  We plan to eventually support remote update within
the browser itself.

Prospero, and thus menus available to the menu browser (as a Prospero
client), supports fine grained access control based on client
identity.  Authentication is provided using 4 alternative
authentication mechanisms, depending on your specific needs: (a)
Kerberos (version 5); (b) per user passwords; (c) trusted port and
trusted host assertion (like the Berkeley R commands); and (d) a check
of the host from which a request originated and the asserted user
identity of the client.

Prospero provides full access control list mechanisms for those who
wish to put fine-grained permissions on particular objects or
directories.  For instance, one can easily set some directories so
that anybody at your company or university can read data in them, only
a particular group of people can insert data into them, and only the
system administrator or the author of a particular piece of
information is allowed to modify and delete it.  Of course, anyone who
does not need these security mechanisms can export data using the
default permissions defined on a per server basis.

An elegant new Prospero feature we're rather proud of is the search
interface.  We support a variety of search methods, including direct
queries to Prospero-speaking database servers, such as Archie servers
and all Gopher servers via a Prospero-Gopher gateway.  The search
servers are self defining, exporting attributes that tell the client
what to prompt for, help messages to display if requested by the user,
and how to package the search when it is sent to the server.

Client implementors need not worry about the generality of this
mechanism since they can make perfectly functional clients that use
only a small subset of the available data.  The menu browser has a
subset of this search interface built into it.

The philosophy behind this work, or why we are doing this:

One of Gopher's greatest strengths is its clear, straightforward user
interface.  However, the gopher protocol itself has a number of
limitations which keep it from being suitable as a universal Internet
information infrastructure, such as the fact that all updates to data
must be made through means outside the protocol (i.e., editing files
on the server) and its lack of security mechanism.

Most current Internet information services, such as Gopher, World Wide
Web, and WAIS, have their own specialized clients, servers, and
network protocols.  This makes it difficult for these services to
interoperate smoothly.  People attempt to address these issues with
inefficient ad-hoc gateways, such as the Gopher servers that make
Archie queries on behalf of Gopher clients, or even our own
Prospero-Gopher gateway.  These are not very good solutions. 

Prospero provides a framework for integrating information from diverse
sources.  Client writers can work on interesting clients, and service
providers can publish their data, without needing to work on issues of
little interest to them.  We explore these ideas in greater depth in
the paper 'Prospero: A Base for Building Information Infrastructure',
to be presented at the INET '93 conference in August, and available
via anonymous FTP from PROSPERO.ISI.EDU as
/pub/papers/prospero/prospero-bii.ps.Z.

We encourage others to build clients that make their queries through
Prospero and to publish their data through Prospero.  We provide an
application library (much better documented in this release than in
previous ones) and a simple application interface designed
specifically for the authors of read-only menu browsers.  It is also
not difficult to publish your data through Prospero, and we are eager
to work with those who wish to do so.

-- Steven Seger Augart
   Research Staff, USC Information Sciences Institute

-- B. Clifford Neuman
   Scientist, USC Information Sciences Institute

email: info-prospero@isi.edu