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Network Working Group                                          C. WeiderRequest for Comments: 1728                    Bunyip Information SystemsCategory: Informational                                    December 1994Resource TranspondersStatus 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, theWeider                                                          [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     resource on a certain time schedule (every 30 days or so) but this      means that the system can be up to 30 days out of date, and this      process can be highly inefficient depending on the percentage of      information that has changed.   2) Conversely, anyone who maintains a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   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 insection 4.1.Weider                                                          [Page 3]

RFC 1728                 Resource Transponders             December 19943.2 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 insection 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 19944.2 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.comWeider                                                          [Page 5]

RFC 1728                 Resource Transponders             December 1994Weider                                                          [Page 6]