rfc1689.txt

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      up the service is one obstacle; maintaining the required databases
      is even more daunting.

   Indexing Services (archie, Veronica, online library catalogs)

      There are several Internet-based projects that build indexed
      catalogs of information to facilitate searching and retrieval.
      The first such services provided network access to library card
      catalogs, with more recent projects indexing network-based
      information.

   archie:

      The archie service began as a simple project to catalog the
      contents of hundreds of ftp-accessible online file archives.  The
      archie service gathers location information, name, and other
      details describing such files and creates an index database.



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      Users can contact an archie server and search this database for
      files they require.

      The archie service is accessible through a range of access
      methods, including telnet, stand-alone client programs running on
      a user's own machine, gopher, WWW, or via electronic mail.  The
      initial implementation of archie tracks over 2,100,000 filenames
      on over 1,200 sites around the world (as of November 1993).  There
      are about 30 (geographically distributed) archie servers.  Both
      commercial and freely available versions of the archie client
      software are available.

      Work continues on extending the archie service to provide
      additional types of information.  The latest version is being used
      to provide a prototype Yellow Pages service and directories of
      online library catalogs and electronic mailing lists.

   Veronica:

      Veronica arose as an attempt to do for the world of Gopher what
      archie did for the world of ftp.  A central server periodically
      scans the complete menu hierarchies of Gopher servers appearing on
      an ever-expanding list (over 2000 sites as of November 1993).  The
      resulting index is provided by a veronica server and can be
      accessed by any gopher client.

   Online library catalogs:

      A large number of libraries make their computerized library
      catalogs available over the Internet.  Most are available through
      telnet sessions in which the user connects to a specific address
      and logs in using a specific login name.  Some are also available
      through other tools, such as Gopher.

   Text-based Indexing Services (WAIS)

   WAIS:

      Wide Area Information Servers (WAIS) is a system for indexing and
      serving information in a network-based environment.  It is
      distinct from indexing tools such as archie and veronica in that
      it is used to index text-based target documents on a server, as
      well as descriptions of the contents of a server.

      A WAIS server allows the administrator to set up an index of the
      documents (or resources) to be published.  The user employs a WAIS
      client to attach to a particular WAIS server, and specifies a
      search pattern which is matched against the server's index.  In



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      early WAIS clients, searches are specified as simple natural-
      language queries; common ("stop") words are removed, and Boolean
      "ORs" are implicitly added between the remaining list of words.
      Matching documents are rank-ordered according to a simple
      statistical weighting scheme which attempts to indicate likely
      relevance.  The user may choose to view selected documents, or
      further refine the search.  The results of one search may be used
      to successively refine future searches ("relevance feedback").
      Gopher clients can also access WAIS servers via a transparent
      gateway.

      Both freely available and commercial versions of WAIS servers and
      clients are available.  Current work is attempting to add Boolean
      expressions and proximity and field specifications to queries.

      There are currently (as of November 1993) some 500 registered WAIS
      databases with an estimated 2000 additional databases that are not
      yet registered.  There are approximately another 100 commercial
      WAIS databases.

6.  NIR Tools

   This section contains detailed information about the various NIR
   Tools.  It is ordered alphabetically.

 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

 ALEX

 Date template updated or checked:  19th March, 1994
 By: Name:             Vincent Cate
     Email address:    [e-mail]

 ----------------------------------------------------------------------

 NIR Tool Name:      Alex

 Brief Description of Tool:

   OVERVIEW:

      The Alex filesystem provides users and applications transparent
      read access to files in anonymous FTP sites on the Internet.
      Today there are thousands of anonymous FTP sites with a total of a
      few millions of files and roughly a terabyte of data.  The
      standard approach to accessing these files involves logging in to
      the remote machine.  This means that an application can not access
      remote files like local files.  This also means that users do not



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      have any of their aliases or local tools available.  Users who
      want to use an application on a remote file first have to manually
      make a local copy of the file.  There is no mechanism for
      automatically updating this local copy when the remote file
      changes.  The users must keep track of where they get their files
      from and check to see if there are updates, and then fetch these.
      In this approach many different users at the same site may have
      made copies of the same remote file each using up disk space for
      the same data.

      Alex addresses the problems with the existing approach while
      remaining within the existing FTP protocol so that the large
      collection of currently available files can be used.  To get
      reasonable performance long term file caching is used.  Thus
      consistency is an issue.  Traditional solutions to the cache
      consistency problem do not work in the Internet FTP domain:
      callbacks are not an option as the FTP protocol has no provisions
      for this and polling over the Internet is slow.  Therefore, Alex
      relaxes file cache consistency semantics, on a per file basis, and
      uses special caching algorithms that take into account the
      properties of the files and of the network to allow a simple
      stateless filesystem to scale to the size of the Internet.

   USER'S VIEW:

      To a user or application, Alex is just a normal filesystem.  Any
      command that works on local files will work on Alex files.  Since
      Alex is a real filesystem, nothing needs to be recompiled and no
      libraries are changed.  Thus, users can apply all of their
      existing skills and tools for using files.

      The user sees a filesystem with a hierarchical name space.  At the
      top level (/alex) there are top-level Internet domains like "edu",
      "com", "uk", and "jp".  Each component of the hostname becomes a
      directory name. Then the remote path is added at the end.  If the
      user does a "ls /alex/edu/berkeley" he sees some machine names
      such as "ucbvax" and "sprite" and some directories on
      berkeley.edu.  From the "ls" it is not clear what is where.  The
      user may or may not be aware of host boundaries.

   INFORMATION PROVIDER'S VIEW:

      Alex is implemented as a user level NFS server.  NFS was chosen
      because it makes it easy to add Alex to a wide range of machines.
      Most machines can simply use the mount command.






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      The model of usage is that there is one Alex server running at
      each institution (though this is not required in any way).  Users
      mount the local server which caches files for users at that site.

      Any information put into any anonymous FTP site becomes available
      via Alex.

 ----------------------------------------------------------------------

 Primary Contact(s):

  Name:                 Vincent Cate

  Email address:        [e-mail]

  Postal Address:       School of Computer Science
                        5000 Forbes Ave.
                        Pittsburgh PA, 15213

  Telephone:            [phone]

  Fax:                  [phone]

 ----------------------------------------------------------------------

 Help Line:

  At this time Alex is a one person project (Vince).

 ----------------------------------------------------------------------

 Related Working Groups:

  Maybe the FTP working group.

 ----------------------------------------------------------------------

 Sponsoring Organization / Funding source:

  Defense Advanced Research Projects Agency, Information Science and
  Technology Office, under the title "Research on Parallel Computing,"
  ARPA Order No.  7330.  Work furnished in connection with this research
  is provided under prime contract MDA972-90-C-0035 issued by DARPA/CMO
  to Carnegie Mellon University.  Vincent Cate is supported by an "Intel
  foundation graduate fellowship".

 ----------------------------------------------------------------------




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 Mailing Lists:

  Address:              [e-mail]

  Administration:       [e-mail]


  Description:          alex-servers is for people setting up an Alex
                        fileserver.

  Archive:              alex.sp.cs.cmu.edu (128.2.209.13)

 ----------------------------------------------------------------------

 News groups:

  None.

 ----------------------------------------------------------------------

 Protocols:

  What is supported:   Any machine that can NFS mount a fileserver.

  What it runs over:   Unix machine and FTP

  Other NIR tools this interworks with:

   Uses FTP sites.

   WAIS can be used to index files in Alex
    (this was done for ftpable-readmes and cs-techreports WAIS servers)

      New versions of archie can output Alex paths.

 Future plans:         Graduate from CMU.

 ----------------------------------------------------------------------

 Servers:

  Date completed or updated:    19 March 1994
  By: Name:                     Vincent Cate

  Platform:                     UNIX

  Primary Contact:
  Name:                         Vincent Cate



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  Email address:                [e-mail]
  Telephone:                    [phone]

  Server software available from:  alex.sp.cs.cmu.edu

  Location of more information:
   No other place to go to.

  Latest version number:
   New versions all the time.

  Brief Scope and Characteristics:
   This software is known to still contain bugs.

  Approximate number of such servers in use:
   200.

  General comments:
   You can use lpr, make, grep, more, etc. on files around the world.

 ----------------------------------------------------------------------

 Clients:

  You just do an NFS mount of the server.  No client software
  is needed.

 ----------------------------------------------------------------------

 Demonstration sites:

  Site name:   alex.sp.cs.cmu.edu

  Access details - do the following as root:
   mkdir /alex
   mount -o timeo=30,retrans=300,soft,intr alex.sp.cs.cmu.edu:/ /alex

  Example use:
   ln -s /alex/edu/cs/cmu/sp/alex/links alexlinks
   cd alexlinks
   ls
   cd cs-tr
   cd ls
   cd purdue
   ls
   lpr TR758.PS





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  If you like Alex and want to use it regularly please find, or set up,
  an Alex fileserver at/near your site.

 ----------------------------------------------------------------------

 Documentation:

  ftp://alex.sp.cs.cmu.edu/www/alex.html
  ftp://alex.sp.cs.cmu.edu/doc/intro.ps
  ftp://alex.sp.cs.cmu.edu/doc/NIR.Tool
  ftp://alex.sp.cs.cmu.edu/doc/alex.post