Danny Amor's Online Library/Danny Amor's Online Library - Volume 1.iso/html/rfc/rfcxxxx/rfc1625

Text File | 1995-07-26 | 15KB | 396 lines

Network Working Group                                      M. St. Pierre
Request for Comments: 1625                                    WAIS, Inc.
Category: Informational                                       J. Fullton
                                                                   CNIDR
                                                               K. Gamiel
                                                                   CNIDR
                                                              J. Goldman
                                                 Thinking Machines Corp.
                                                                B. Kahle
                                                              WAIS, Inc.
                                                                J. Kunze
                                                             UC Berkeley
                                                               H. Morris
                                                              WAIS, Inc.
                                                        F. Schiettecatte
                                                           FS Consulting
                                                               June 1994


                         WAIS over Z39.50-1988

Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

1. Introduction

   The network publishing system, Wide Area Information Servers (WAIS),
   is designed to help users find information over a computer network.
   The principles guiding WAIS development are:

         1. A wide-area networked-based information system for searching,
            browsing, and publishing.
         2. Based on standards.
         3. Easy to use.
         4. Flexible and growth oriented.

   From this basis, a large group of developers, publishers, standards
   bodies, libraries, government agencies, schools, and users have been
   helping further the WAIS system.

   The WAIS software architecture has four main components: the client,
   the server, the database, and the protocol.  The WAIS client is a
   user-interface program that sends requests for information to local
   or remote servers.  Clients are available for most popular desktop
   environments.  The WAIS server is a program that services client



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   requests, and is available on a variety of UNIX platforms.  The
   server generally runs on a machine containing one or more information
   sources, or WAIS databases.  The protocol, Z39.50-1988, is used to
   connect WAIS clients and servers and is based on the 1988 Version of
   the NISO Z39.50 Information Retrieval Service and Protocol Standard.
   The goal of the WAIS network publishing system is to create an open
   architecture of information clients and servers by using a standard
   computer-to-computer protocol that enables clients to communicate
   with servers.

   WAIS development began in October 1989 with the first Internet
   release occurring in April 1991.  From the beginning, WAIS committed
   to use the Z39.50-1988 standard as the information retrieval protocol
   between WAIS clients and servers.  The implementation is still in use
   today by existing WAIS clients and servers resulting in over 50,000
   users of Z39.50-1988 on the Internet.

2. Purpose

   The purpose of this memo is to initiate a discussion for a migration
   path of the WAIS technology from Z39.50-1988 Information Retrieval
   Service Definitions and Protocol Specification for Library
   Applications [1] to Z39.50-1992 [2] and then to Z39.50-1994 [3].  The
   purpose of this memo is not to provide a detailed implementation
   specification, but rather to describe the high-level design goals and
   functional assumptions made in the WAIS implementation of Z39.50-
   1988.  WAIS use of Z39.50-1992 and Z39.50-1994 standards will be the
   subject of future RFCs.

3. Historical Design Goals of WAIS

   As an aid to understanding the original WAIS implementation and its
   use of Z39.50-1988, the historical design goals of WAIS are presented
   in this section.  Included with each goal is a brief description of
   the assumptions used to meet these design goals.

         1. Provide users access to bibliographic and non-bibliographic
            information, including full-text and images.

   Because Z39.50-1988 grew out of the bibliographic community,
   additional assumptions with the protocol were required to serve non-
   bibliographic information.  They were also necessary to serve
   documents existing in multiple formats (e.g., rtf, postscript, gif,
   etc.).

         2. Keep the client/server interface simple and independent of
            changes in the functionality of the server.




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   To achieve this, the text string entered by the user was transmitted
   to the server without parsing the string into a Type-1 RPN (reverse-
   polish notation) query, as is common for bibliographic applications.
   Instead WAIS defined a new Type-3 query containing the text string.
   In this way, knowledge of the Z39.50 Attributes supported by the
   server was no longer required by the client or the user, as is true
   of many existing Z39.50 implementations.  In addition, the client
   software did not require modification to support the evolving
   functionality of the server.

         3. Provide relevance feedback capability.

   Relevance feedback is the ability to select a document, or portion of
   a document, and find a set of documents similar to the selection.
   WAIS included documents used in relevance feedback as part of the
   Type-3 query.

         4. Permit the server to operate in a stateless manner.

   A WAIS server was designed to be "stateless", meaning that search
   result sets were not stored by the server.  In Z39.50 terms, the
   server exercised its right to unilaterally delete a result set as
   soon as it sent the search response.  For this reason, the Present
   Facility of Z39.50 was not used, and retrievals were performed using
   the Search Facility.  Relaxing this constraint in future
   implementations may prove the most prudent path.

         5. Provide the ability for a client to retrieve documents in
            pieces.

   Because retrieval of a portion of a document could be done several
   ways with Z39.50-1988, specific assumptions were made to implement
   this functionality.  Accessing a portion of a document was required
   for both retrieval and for relevance feedback.

         6. Run over TCP.

   The Z39.50-1988 standard was designed to run in the application layer
   using the presentation services provided by the Open Systems
   Interconnection (OSI) Reference Model.  Due to the popularity of
   TCP/IP and the Internet, WAIS was designed to run over TCP.  Use of
   Z39.50 over TCP is described in [4].

4. WAIS Implementation of Z39.50-1988

   By working with the Z39.50 Implementors Group (ZIG), the WAIS
   developers used a recommended subset of Z39.50-1988 and specific
   assumptions to fulfill its requirements.  Over time, many of these



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   requirements have then gone into the definition of subsequent
   versions of Z39.50.  As new requirements become apparent, WAIS will
   document any additional assumptions and work with the ZIG in
   developing extensions.

   WAIS supported the Init and Search Facilities of Z39.50-1988.  Both
   search and retrieval were implemented using the Search Facility, as
   described in this section.

   Search was initiated by the client with a Search Request APDU
   (Application Protocol Data Unit) using a Type-3 query.  The query
   contained two main fields:

         1. The "seed words", or text, typed by the user.
         2. A list of document objects, where a document object is a
            full document, or portion thereof, to be used in relevance
            feedback.  Each document object contains a document
            identifier (Doc-ID) [5], type, chunk-code, and start and
            end locations.  The Doc-ID and type specify the location and
            format, respectively, of the document.  The chuck-code
            determines the unit of measure for the start and end
            locations.  Examples of chunk-codes used include
            byte, line, paragraph, and full document.  If the chunk code
            is a full document, the start and end locations are ignored.

   A Search Response APDU returned by the server contained a relevance
   ranked list of records, or WAIS Citations.  A WAIS Citation refers to
   a document on the server.  Each WAIS Citation contains the following
   fields:

         1. Headline - a set of words that convey the main idea of the
            document.
         2. Rank - the numerical score of the document based on its
            relevance to the query, normalized to a top score of 1000.
         3. List of available formats - e.g. text, postscript, tiff, etc.
         4. Doc-ID - the location of the document.
         5. Length - the length of the document in bytes.

   The number of WAIS Citations returned was limited by the preferred
   message size negotiated during the Init.

   Retrieval of a document was initiated by the client with a Search
   Request APDU using a Type-1 query.  The query contained up to four
   terms:

         1. Term: Doc-ID
            Use Attribute: system-control-number      code = "un"
            Relation Attribute: equal                 code = "re"



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         2. Term: the requested document format
            Use Attribute: data-type                  code = "wt"
            Relation Attribute: equal                 code = "re"
         3. Term: the start location
            Use Attribute: paragraph, line, byte      code = "wp", "wl",
                                                             "wb"
            Relation Attribute: greater-than-or-equal code = "ro"
         4. Term: the end location
            Use Attribute: paragraph, line, byte      code = "wp", "wl",
                                                             "wb"
            Relation Attribute: less-than             code = "rl"

   Because full-text and images were often larger in size than the
   receive buffer of the client, clients were designed to optionally
   retrieve documents in chunks, specifying the start and end positions
   of the chunk in the query.  An example of a fully-specified retrieval
   query is:

   query = ( ( use = "un", relation = "re", term = <Doc-ID> )
             AND
             ( use = "wt", relation = "re", term = postscript )
             AND
             ( use = "wb", relation = "ro", term = 0 )
             AND
             ( use = "wb", relation = "ro", term = 2000 )
            )

   A retrieval response was issued by the server with a Search Response
   APDU. In this case a single record corresponding to the requested
   document, or portion thereof, was returned in the specified format.

5.  Security Considerations

   Security issues are not discussed in this memo.

6.  References

   [1] National Information Standards Organization (NISO).  American
       National Standard Z39.50, Information Retrieval Service
       Definition and Protocol Specifications for Library Applications,
       New Brunswick, NJ, Transaction Publishers; 1988.

   [2] ANSI/NISO Z30.50-1992 (version 2) Information Retrieval Service
       and Protocol: American National Standard, Information Retrieval
       Application Service Definition and Protocol Specification for
       Open Systems Interconnection, 1992.





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   [3] Z39.50 Version 3: Draft 8", October 1993.  Maintenance Agency
       Reference: Z39.50MA-034.

   [4] Lynch, C., "Using the Z39.50 Information Retrieval Protocol
       in the Internet Environment", Work in Progress, November 1993.

   [5] "Document Identifiers, or International Standard Book Numbers
       for the Electronic Age", Brewster Kahle, Thinking Machines
       Corporation, see URL=<ftp://wais.com/pub/protocol/doc-ids.txt>,
       September 1991.

7.  Authors' Addresses

   Margaret St. Pierre
   WAIS Incorporated
   1040 Noel Drive
   Menlo Park, California  94025

   Phone: (415) 327-WAIS
   Fax:   [phone]
   EMail: [e-mail]


   Jim Fullton
   Clearinghouse for Networked Information
   Discovery & Retrieval
   3021 Cornwallis Road
   Research Triangle Park, North Carolina  27709-2889

   Phone: [phone]
   Fax:   [phone]
   EMail: [e-mail]


   Kevin Gamiel
   Clearinghouse for Networked Information
   Discovery & Retrieval
   3021 Cornwallis Road
   Research Triangle Park, North Carolina  27709-2889

   Phone: [phone]
   Fax:   [phone]
   EMail: [e-mail]








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   Jonathan Goldman
   Thinking Machines Corporation
   1010 El Camino Real, Suite 310
   Menlo Park, California  94025

   Phone: [phone] x229
   Fax:   [phone]
   EMail: [e-mail]


   Brewster Kahle
   WAIS Incorporated
   1040 Noel Drive
   Menlo Park, California  94025

   Phone: (415) 327-WAIS
   Fax:   [phone]
   EMail: [e-mail]


   John A. Kunze
   UC Berkeley
   289 Evans Hall
   Berkeley, California  94720

   Phone: [phone]
   Fax: [phone]
   EMail: [e-mail]


   Harry Morris
   WAIS Incorporated
   1040 Noel Drive
   Menlo Park, California  94025

   Phone: (415) 327-WAIS
   Fax:   [phone]
   EMail: [e-mail]


   Francois Schiettecatte
   FS Consulting
   435 Highland Avenue
   Rochester, New York  14620

   Phone: [phone]
   EMail: [e-mail]




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