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+Network Working Group                                          C. Weider
+Request for Comments: 1728                    Bunyip Information Systems
+Category: Informational                                    December 1994
+
+
+                         Resource Transponders
+
+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.
+
+Abstract
+
+   Although a number of systems have been created in the last several
+   years to provide resource location and navigation on the Internet,
+   the information contained in these systems must be maintained and
+   updated by hand.  This paper describes an automatic mechanism, the
+   resource transponder, for maintaining resource location information.
+
+Author's Note:
+
+   This document is being circulated as sort of a research paper;
+   consequently there are no protocol specifications or anything of the
+   sort.  I hope that we can go from here and actually design them if
+   there's consensus that they are potentially useful. Once we have some
+   idea of the required functionality, we can then go out and
+   standardize them.
+
+Disclaimer
+
+   This paper represents only the opinions of the author; it does not
+   represent the consensus of the IIIR Working Group, although it is
+   recognized by them as one legitimate approach to a solution of the
+   problem.
+
+1. Introduction
+
+   In the past few years, we've seen the invention and growth of a
+   number of information location systems on the Internet, e.g., archie,
+   Gopher, and WAIS.  However, as these systems have become widely
+   deployed, a number of maintenance and security problems have arisen
+   with them.  Some of the major ones:
+
+   1) Out of necessity, most of these systems contain pointers to the
+      desired resources rather than the resources themselves. Therefore,
+      if a resource becomes obsolete, is modified, or is moved, the
+
+
+
+Weider                                                          [Page 1]
+
+RFC 1728                 Resource Transponders             December 1994
+
+
+      location system must be updated by hand. Some systems (archie in
+      particular) proactively create updated indexes by contacting every
+      resource on a certain time schedule (every 30 days or so) but this
+      means that the system can be up to 30 days out of date, and this
+      process can be highly inefficient depending on the percentage of
+      information that has changed.
+
+   2) Conversely, anyone who maintains a resource that they wish indexed
+      must keep track of every directory which contains a pointer to
+      that resource, so that if it is modified, all the directories can
+      be updated. This obviously is an optimistic scenario.
+
+   3) Many organizations which have installed these systems do not have
+      the the available resources or expertise to maintain the
+      information in the systems. Thus we have long periods where the
+      information drifts, then a short period when the information is
+      updated again.
+
+   4) Even though these systems are almost always out of date today,
+      this problem will become increasingly harder for humans to manage
+      by hand as everyone on the net becomes their own publisher. Also,
+      as the net speeds up and people rely more and more on accurate
+      information, human-induced delays in updates of these systems will
+      become increasingly intolerable.
+
+   5) Most, if not all, of these systems provide no security whatsoever;
+      if a pointer to a resource appears in a locator system, then it is
+      assumed to be meant for public consumption. There are many
+      potential information providers who would like to use publicly
+      deployed information systems to publish to a very selected
+      clientele, and do not wish to allow the whole net access to their
+      resources.
+
+2. Requirements for a Solution
+
+   There are several objectives which must be met by any proposed
+   solution to these problems:
+
+   1) We need to decrease the personnel resources needed for indexing
+      and pointer maintenance.
+
+   2) We need to increase the reliability and accuracy of the
+      information held in resource location systems.
+
+   3) We need to provide some mechanisms for security, particularly by
+      mediating access to the resources.
+
+
+
+
+
+Weider                                                          [Page 2]
+
+RFC 1728                 Resource Transponders             December 1994
+
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+   4) We need to make it easy for non-experts, such as librarians,
+      archivists, and database maintainers, to announce their new
+      resources to the various resource location services.
+
+   Many of these problems can be solved by a 'resource transponder'
+   mechanism.
+
+3. Resource Transponders
+
+   The resource transponder system works by adding two new layers to
+   every resource: metainformation and an agent to update a resource
+   location system (RLS) with that metainformation. The metainformation
+   layer is physically attached to every resource, so that when the
+   resource is moved or altered, the metainformation is immediately
+   available to update the RLS. The agent layer may also be attached to
+   the resource or may not be; the implications of both of these options
+   are discussed in detail below.
+
+   3.1 Metainformation
+
+   The metainformation layer of a given resource contains any
+   information which might be required to create a pointer to this
+   resource, and any information which may be useful for indicating how
+   to catalog or index the resource.  For example, the metainformation
+   layer of a text document might contain such things as the Uniform
+   Resource Name (URN) of the document (this is sort of a ISBN number
+   for electronic resources), the title of the document, a Uniform
+   Resource Locator (URL) for the document (this is a combination net
+   address and access method indicator, used for retrieval), the size of
+   the document, etc. Thus the metainformation layer contains data about
+   the resource to which it is attached.
+
+   This metainformation is expected to be modifiable. For example, the
+   metainformation layer may contain a history of where this particular
+   copy of a resource has been.  Let's say that a resource/transponder
+   pair has been moved. When it gets to its new location, the agent can
+   then attempt to contact the resource at its old location to determine
+   whether the resource is still there (in which case the agent will
+   simply cause the new location to be added to the RLS) or whether the
+   resource is not there (in which case the agent can tell the RLS to
+   add the current pointer and delete the old one).
+
+   A number of other possibilities for the contents of the
+   metainformation level are contained in section 4.1.
+
+
+
+
+
+
+
+Weider                                                          [Page 3]
+
+RFC 1728                 Resource Transponders             December 1994
+
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+3.2 Agents
+
+   The agent layer of a given resource contains an executable program
+   which is responsible for reading the metainformation attached to the
+   resource and using that information to update a RLS. It is also
+   responsible for updating the metainformation where necessary and for
+   running any indexing programs required by the RLS it is attempting to
+   update.
+
+   When the tools required to build agents are constructed and deployed,
+   the author expects the agents to begin mediating access to the
+   resource, particularly for agents attached to resources which are not
+   currently considered active processes, such as text files and
+   digitized images.  In this futuristic model, someone wishing to read
+   a given document would have to first negotiate access to the data
+   with the agent; the agent would then be responsible for delivering
+   the data to the client. However, it is expected that this type of
+   agent will not be widely deployed for some time.
+
+   Different ways of implementing agents are discussed in section 4.2.
+
+4. Models for implementations of resource transponders
+
+   4.1. Models for implementations of the metainformation layer
+
+   The metainformation layer can be impelemented in a number of ways,
+   depending on the resource with which it is associated. For an
+   'active' resource, such as an on-line catalog or a mail-based
+   service, the metainformation can be stored in a file with a well-
+   known name in the software distribution.  Alternatively, the
+   metainformation could be stored as a record in the data which the
+   resource serves. For a text document, the metainformation could be
+   stored as the first or last N bytes of the document (which would
+   break a number of editors and file display techniques, but would
+   guarantee that the metainformation is moved with the resource), or
+   perhaps as a file with a logically associated name (paper2.meta
+   associated with paper2.txt, for example).  The problem with this
+   second approach is that the user must know that they have to move the
+   metainformation with the file itself, or things will start breaking.
+   If an agent is explicitly attached to the resource, the agent could
+   contain the metainformation internally.
+
+   In any case, the resource transponder system must be able to
+   guarantee that the metainformation is moved when the resource is
+   moved.
+
+
+
+
+
+
+Weider                                                          [Page 4]
+
+RFC 1728                 Resource Transponders             December 1994
+
+
+4.2 Models for implementations of the agents
+
+   The agent layer can also be implemented in a number of ways,
+   depending on such things as system loads, desired sizes of resources,
+   multitasking capabilities, etc.
+
+   The easiest and for many unitasking systems the cleanest way of
+   implementing an agent is to have one agent per computer. Then when a
+   resource is moved onto that computer, the agent is explicitly
+   activated and notified where the new resource is. For example, let's
+   say that someone wishes to download a copy of a resource and then let
+   the RLS know that that resource is available for public consumption.
+   She would download the resource and then run the agent, which would
+   then notify the RLS and update the metainformation attached to the
+   resource. This model could also be used to track files on a LAN, or
+   to provide local location services with no need to run a larger RLS.
+
+   Another model for implementation of the agent is to have one agent
+   per resource. In this model, the agent would be moved along with the
+   resource and the metainformation. The agent could be implemented in a
+   file which would be associated with the resource; in that case the
+   agent would have to be explicitly activated when the resource was
+   moved. Alternatively, the agent/metainformation/resource system could
+   be implemented as one system, or in one file. In this case, the agent
+   itself would always be active, and would be responsible for mediating
+   access to the resource.  When one did a 'telnet' to a resource with
+   an active agent, the agent would accept the telnet connection and be
+   responsible for providing security and translation for the data. This
+   could provide great security for resources while still allowing
+   pointers to them to be placed in public RLS's; the data in the
+   resource could be encrypted, with the agent responsible for
+   decrypting it.
+
+5. Security Considerations
+
+   Security issues are discussed throughout this memo.
+
+6. Author's Address
+
+   Chris Weider
+   Bunyip Information Systems, Inc.
+   2001 S. Huron Parkway, #12
+   Ann Arbor, MI 48104
+   USA
+
+   Phone: +1 313-971-2223
+   Fax: +1 313-971-2223
+   EMail: clw@bunyip.com
+
+
+
+Weider                                                          [Page 5]
+
+RFC 1728                 Resource Transponders             December 1994
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+Weider                                                          [Page 6]
+