rfc1781.txt

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RFC 1781                  User Friendly Naming                March 1995


4.5  Bottom Level

   The "Bottom Level" is to deal with leaf entries in the DIT. This will
   often be a person, but may also be a role, an application entity or
   something else.

   The last component of a purported name may either reference a leaf or
   non-leaf.  For this reason, both should be tested for.  As a
   heuristic, if the base object for the search has two or more
   components it should be tested first as a bottom level name and then
   intermediate.  Reverse this for shorter names.  This optimises for
   the (normal) case of non-leaves high up the tree and leaves low down
   the tree.

   For bottom level names, make an approximate and substring match
   against Common Name, Surname, and User ID. Where common name is
   looked for, a full subtree search will be used when at the second
   level of the DIT or lower, otherwise a single level search.

   For example, if I have resolved a purported name to the distinguished
   name

   University College London, GB

   and have a single component Bloggs, this will generate a subtree
   search.

5.  Examples

   This is all somewhat confusing, and a few examples are given.  These
   are all in the context of the environment shown in Table 1 on Page
   13.

   If "Joe Bloggs" is supplied, a subtree search of

   Physics, University College London, GB

   will be made, and the user prompted for "Joseph Z. Bloggs" as the
   only possible match.

   If "Computer Science" is supplied, first

   Physics, University College London, GB

   will be searched, and the user will reject the approximate match of
   "Colin Skin".  Then a subtree search of

   University College London, GB



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   will be made, looking for a person.  Then a single level search will
   be made looking for Org Unit, and

   Computer Science, University College London, GB

   will be returned without prompting (exact match).  Supplying "Steve
   Kille" will lead to a failed subtree search of

   Physics, University College London, GB

   and lead straight to a subtree search of

   University College London, GB

   This will lead to an exact value match, and so a single entry
   returned without prompting.

   If "Andrew Findlay, Brunel" is supplied, the first element of the
   environment will be skipped, single level search of "Brunel" under
   "GB" will find:

   Brunel University, GB

   and a subtree search for "Andrew Findlay" initiated.  This will yield

   Andrew Findlay, Computing and Media Services, Brunel University, GB

   Dr A J Findlay, Manufacturing and Engineering Systems, Brunel
   University, GB

   and the user will be prompted with a choice.

   This approach shows how a simple format of this nature will "do the
   right thing" in many cases.

6.  Support required from the standard

   Fortunately, all that is needed is there!  It would be useful to have
   "friendly country name" as a standard attribute.

7.  Support of OSI Services

   The major focus of this work has been to provide a mechanism for
   identifying Organisations and Users.  A related function is to
   identify applications.  Where the Application is identified by an AET
   (Application Entity Title) with an RDN of Common Name, this
   specification leads to a natural usage.  For example, if a filestore
   is named "gannet", then this could easily be identified by the name:



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   Gannet, Computer Laboratory, Cambridge University, GB

   In normal usage, this might lead to access (using a purported name)
   of:

   FTAM gannet,cambridge

   A second type of access is where the user identifies an Organisation
   (Organisational Unit), and expects to obtain a default service.  The
   service is implied by the application, and should not require any
   additional naming as far as the user is concerned.  It is proposed
   that this is supported by User Friendly Naming in the following way.

   1.  Determine that the purported name identifies a non-leaf object,
       which is of object class Organisation or Organisational Unit or
       Locality.

   2.  Perform a single level search for Application Entities which
       support the required application contexts.  This assumes that all
       services which are supporting default access for the organisation
       are registered at one level below (possibly by the use of
       aliases), and that other services (specific machines or parts of
       the organisation) are represented further down the tree.  This
       seems to be a reasonable layout, and its utility can be evaluated
       by experiment.

8.  Experience

   An experimental implementation of this has been written by Colin
   Robbins.  The example in Figure 1 shows that it can be very effective
   at locating known individuals with a minimum of effort.  This code has
   been deployed within the "FRED" interface of the PSI Pilot [9], and
   within an prototype interface for managing distribution lists.  The
   user reaction has been favourable:

   Some issues have arisen from this experience:

    o  Where there is more than one level of Organisational Unit, and the
       user guesses one which is not immediately below the organisation,
       the algorithm works badly.  There does not appear to be an easy
       fix for this.  It is not clear if this is a serious deficiency.

    o  Substring searching is currently done with leading and trailing
       wildcards.  As many implementations will not implement leading
       wildcards efficiently, it may be preferable to only use trailing
       wildcards.  The effect of this on the algorithm needs to be
       investigated.




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RFC 1781                  User Friendly Naming                March 1995


   Implementors of this specification are encouraged to investigate
   variants of the basic algorithm.  A final specification should depend
   on experience with such variants.

9.  Relationship to other work

   Colin Robbin's work on the interface "Tom" and implementation of a
   distribution list interface strongly influenced this specification
   [6].

   Some of the ideas used here originally came from a UK Proposal to the
   ISO/CCITT Directory Group on "New Name Forms" [2].  This defined, and
   showed how to implement, four different types of names:

   Typed and Ordered The current Distinguished Name is a restricted
   example of this type of name.



































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   -> t hales, csiro, australia
   Found good match(es) for 'australia'
   Found exact match(es) for 'csiro'
   Please select from the following:
      Trevor Hales, OC, HPCC, DIT, IICT, CSIRO, AU [y/n] ? y
   The following were matched...
      Trevor Hales, OC, HPCC, DIT, IICT, CSIRO, AU

   -> g michaelson, queensland, au
   Found exact match(es) for 'au'
   Please select from the following:
      University of Queensland, AU [y/n] ? y
      Axolotl, AU [y/n] ? n
   Please select from the following:
      George Michaelson, Prentice Computer Centre, University of
      Queensland, AU
   [y/n] ? y
      Manager, University of Queensland, AU [y/n] ? n
   The following were matched...
      George Michaelson, Prentice Computer Centre, University of
      Queensland, AU

   -> r needham, cambridge
   Found good match(es) for 'cambridge'
   Please select from the following:
      Roger Needham, Computer Lab, Cambridge University [y/n] ? y
   The following were matched...
      Roger Needham, Computer Lab, Cambridge University

   -> kirstein
   Found good match(es) for 'kirstein'
   The following were matched...
      Peter Kirstein


              Figure 1:  Example usage of User Friendly Naming

   Untyped and Ordered

   This is the type of name proposed here (with some extensions to allow
   optional typing).  It is seen as meeting the key user requirement of
   disliking typed names, and is efficient to implement.

   Typed and Unordered

   This sort of name is proposed by others as the key basis for user
   friendly naming.  Neufeld shows how X.500 can be used to provide this
   [7], and Peterson proposes the Profile system to provide this [8].



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   The author contends that whilst typed naming is interesting for some
   types of searching (e.g., yellow page searching), it is less
   desirable for naming objects.  This is borne out by operational
   experience with OSI Directories [3].

   Untyped and Unordered

   Surprisingly this form of name can be supported quite easily.
   However, a considerable gain in efficiency can be achieved by
   requiring ordering.  In practice, users can supply this easily.
   Therefore, this type of name is not proposed.

10.  Issues

   The following issues are noted, which would need to be resolved
   before this document is progressed as an Internet Standard.

   Potential Ambiguity

   Whilst the intention of the notation is to allow for specification of
   alternate values, it inherently allows for ambiguous names to be
   specified.  It needs to be demonstrated that problems of this
   characteristic are outweighed by other benefits of the notation.

   Utility

   Determine that the specification is being implemented and used.

   Performance

   Measurements on the performance implications of using this approach
   should be made.

   Alogrithm

   The utility of the algorithm, and possible variants, should be
   investigated.

   This format, and the procedures for resolving purported names, should
   be evolved to an Internet Standard.  The syntax can be expected to be
   stable.  In light of experience, the algorithm for resolving
   purported names may be changed.









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RFC 1781                  User Friendly Naming                March 1995


11.  References

   [1] The Directory --- overview of concepts, models and services,
       1993. CCITT X.500 Series Recommendations.

   [2] S.E. Kille. New name forms, May 1989.  ISO/IEC/JTC 21/ WG4/N797
       UK National Body Contribution to the Oslo Directory Meeting.

   [3] S.E. Kille. The THORN large scale pilot exercise.  Computer
       Networks and ISDN Systems, 16(1):143--145, January 1989.

   [4] S.E. Kille. Using the OSI directory to achieve user friendly
       naming. Research Note RN/20/29, Department of Computer Science,
       University College London, February 1990.

   [5] Kille, S., "A String Representation of Distinguished Names", RFC
       1779, ISODE Consortium, March 1995.

   [6] S.E. Kille and C.J. Robbins. The ISO development environment:
       User's manual (version 7.0), July 1991. Volume 5:  QUIPU.

   [7] G.W. Neufeld. Descriptive names in X.500.  In SIGCOMM 89
       Symposiun Communications Architectures and Protocols, pages 64--
       71, September 1989.