Network Working Group C. Weider
Request for Comments: 1727 P. Deutsch
Category: Informational Bunyip Information Systems
December 1994
A Vision of an Integrated Internet Information Service
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
This paper lays out a vision of how Internet information services
might be integrated over the next few years, and discusses in some
detail what steps will be needed to achieve this integration.
Acknowledgments
Thanks to the whole gang of information service wonks who have
wrangled with us about the future of information services in
countless bar bofs (in no particular order): Cliff Lynch, Cliff
Neuman, Alan Emtage, Jim Fullton, Joan Gargano, Mike Schwartz, John
Kunze, Janet Vratny, Mark McCahill, Tim Berners-Lee, John Curran,
Jill Foster, and many others. Extra special thanks to George Brett of
CNIDR and Anders Gillner of RARE, who have given us the opportunity
to start tying together the networking community and the librarian
community.
1. Disclaimer
This paper represents only the opinions of its authors; it is not an
official policy statement of the IIIR Working Group of the IETF, and
does not represent an official consensus.
2. Introduction
The current landscape in information tools is much the same as the
landscape in communications networks in the early 1980's. In the
early 80's, there were a number of proprietary networking protocols
that connected large but autonomous regions of computers, and it was
difficult to coalesce these regions into a unified network. Today, we
have a number of large but autonomous regions of networked
information. We have a vast set of FTPable files, a budding WAIS
network, a budding GOPHER network, a budding World Wide Web network,
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RFC 1727 Resource Transponders December 1994
etc. Although there are a number of gateways between various
protocols, and information service providers are starting to use
GOPHER to provide a glue between various services, we are not yet in
that golden age when all human information is at our fingertips. (And
we're even farther from that platinum age when the computer knows
what we're looking for and retrieves it before we even touch the
keyboard.)
In this paper, we'll propose one possible vision of the information
services landscape of the near future, and lay out a plan to get us
there from here.
3. Axioms of information services
There are a number of unspoken assumptions that we've used in our
discussions. It might be useful to lay them out explicitly before we
start our exploration.
The first is that there is no unique information protocol that will
provide the flexibility, scale, responsiveness, worldview, and mix of
services that every information consumer wants. A protocol designed
to give quick and meaningful access to a collection of stock prices
might look functionally very different from one which will search
digitized music for a particular musical phrase and deliver it to
your workstation. So, rather than design the information protocol to
end all information protocols, we will always need to integrate new
search engines, new clients, and new delivery paradigms into our
grand information service.
The second is that distributed systems are a better solution to
large-scale information systems than centralized systems. If one
million people are publishing electronic papers to the net, should
they all have to log on to a single machine to modify the central
archives? What kind of bandwidth would be required to that central
machine to serve a billion papers a day? If we replicate the central
archives, what sort of maintenance problems would be encountered?
These questions and a host of others make it seem more profitable at
the moment to investigate distributed systems.
The third is that users don't want to be bothered with the details of
the underlying protocols used to provide a given service. Just as
most people don't care whether their e-mail message gets split up
into 20 packets and routed through Tokyo to get to its destination,
information service users don't care whether the GOPHER server used
telnet to get to a WAIS database back-ended by an SQL database. They
just want the information. In short, they care very much about how
they interact with the client; they just don't want to know what goes
on behind.
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These axioms force us to look at solutions which are distributed,
support multiple access paradigms, and allow information about
resources to be handed off from one system (say Gopher) to another
(say WWW).
4. An architecture to provide interoperability and integration.
The basic architecture outlined in this paper splits up into 4 levels
[Fig. 1].
At the lowest level, we have the resources themselves. These are such
things as files, telnet sessions, online library catalogs, etc. Each
resource can have a resource transponder attached [Weider 94a], and
should have a Uniform Resource Name (URN) [Weider 94b] associated
with it to uniquely identify its contents. If a resource transponder
is attached, it will help maintain the information required by the
next level up.
At the next level, we have a 'directory service' that takes a URN and
returns Uniform Resource Locators (URLs) [Berners-Lee 94] for that
resource. The URL is a string which contains location information,
and can be used by a client to access the resource pointed to by the
URL. It is expected that a given resource may be replicated many
times across the net, and thus the client would get a number of URLs
for a given resource, and could choose between them based on some
other criteria.
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______________________________________________________________
| | | | |
| | | | |
| Gopher | WAIS | WWW | Archie | Others ...
| | | | |
|___________|______________|_______|_______________|___________
| |
| _________|____________
| | |
| | Resource Discovery |
| | System (perhaps |
| | based on whois++) |
| |______________________|
| |
| |
_____|________________________________|____
| |
| Uniform resource name to uniform resource |
| locator mapping system (perhaps based on |
| whois++ or X.500) |
|___________________________________________|
|
|
________________|______________________________________
| | | |
______|______ _______|_____ ______|______ ______|______
| | | | | | | |
| Transponder | | Transponder | | Transponder | | Transponder |
|_____________| |_____________| |_____________| |_____________|
| | | | | | | |
| | | | | | | |
| | | | | | | |
| Resource | | Resource | | Resource | | Resource |
| | | | | | | |
| | | | | | | |
|_____________| |_____________| |_____________| |_____________|
Figure 1: Proposed architecture of an integrated information
service
The third level of the architecture is a resource discovery system.
This would be a large, distributed system which would accept search
criteria and return URNs and associated information for every
resource which matched the criteria. This would provide a set of URLs
which the information service providers (GOPHER servers, etc.) could
then select among for incorporation.
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RFC 1727 Resource Transponders December 1994
The fourth level of the architecture is comprised of the various
information delivery tools. These tools are responsible for
collating pointers to resources, informing the user about the
resources to which they contain pointers, and retrieving the
resources when the user wishes.
Let's take a look in greater detail at each of these levels.
4.1 Resource layer
The resources at this layer can be any collection of data a publisher
wishes to catalog. It might be an individual text file, a WAIS
database, the starting point for a hypertext web, or anything else.
Each resource is assigned a URN by the publisher, and the URL is
derived from the current location of the resource. The transponder is
responsible for updating levels 2 and 3 with the appropriate
information as the resource is published and moves around.
4.2 URN -> URL mapping
This level takes a URN and returns a number of URLs for the various
instantiations of that resource on the net. It will also maintain
the URN space. Thus the only functionality required of this level is
the ability to maintain a global namespace and to provide mappings
from that namespace to the URLs. Consequently, any of the distributed
'directory service' protocols would allow us to provide that service.
However, there may be some benefit to collapsing levels 2 and 3 onto
the same software, in which case we may need to select the underlying
protocol more carefully. For example, X.500 provides exactly the
functionality required by level 2, but does not (yet) have the
functionality required to provide the level 3 service. In addition,
the service at level 2 does not necessarily have to be provided by a
monolithic system. It can be provided by any collection of protocols
which can jointly satisfy the requirements and also interoperate, so
that level 2 does appear to level 3 to be universal in scope.
4.3 Resource discovery
This is the level which requires the most work, and where the
greatest traps lurk to entangle the unwary. This level needs to serve
as a giant repository of all information about every publication,
except for that which is required for the URI -> URL mapping. Since
this part is the least filled in at the moment, we will propose a
mechanism which may or may not be the one which is eventually used.
When a new resource is created on the network, it is assigned a URN
determined by the publisher of the resource. Section 4.1 discusses in
more detail the role of the publisher on the net, but at the moment
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we can consider only 2 of the publisher's functions. The publisher is
responsible for assigning a URN out of the publishers namespace, and
is responsible for notifying a publishing agent [Deutsch 92] that a
new resource has been created; that agent will either be a part of
the resource location service or will then take the responsibility
for notifying an external resource location service that the resource
has been created. Alternatively, the agent can use the resource
location service to find parts of the RLS which should be notified
that this resource has been created.
To give a concrete example, let's say that Peter and Chris publish a
multi- media document titled, "Chris and Peter's Bogus Journey",
which talks about our recent trip to the Antarctic, complete with
video clips. P & C would then ask their publishing agent to generate
a URN for this document. They then ask their publishing agent to
attach a transponder to the document, and to look around and see if
anyone a) has asked that our agent notify them whenever anything we
write comes out; or b) is running any kind of server of 'trips to
Antarctica'. Janet has posted a request that she be notified, so the
agent tells her that a new resource has been created. The agent also
finds 3 servers which archive video clips of Antarctica, so the agent
notifies all three that a new resource on Antarctica has come out,
and gives out the URN and a URL for the local copy.
4.4 Information delivery tools
One of the primary functions of an information delivery tool is to
collect and collate pointers to resources. A given tool may provide
mechanisms to group those pointers based on other information about
the resource, e.g. a full-text index allows one to group pointers to
resources based on their contents; archie can group pointers based on
filenames, etc. The URLs which are being standardized in the IETF are
directly based on the way World Wide Web built pointers to resources,
by creating a uniform way to specify access information and location
for a resource on the net. With just the URLs, however, it is
impossible without much more extensive checking to tell whether two
resources with different URLs have the same intellectual content or
not. Consequently, the URN is designed to solve this problem.
In this architecture, the pointers that a given information delivery
tool would keep to a resource will be a URN and one or more cached
URLs. When a pointer to a resource is first required (i.e. when a new
resource is linked in a Gopher server), level 2 will provide a set of
URLs for that URN, and the creator of the tool can then select which
of those will be used. As it is expected that the URLs will
eventually become stale (the resource moves, the machine goes down,
etc.) the URN can be used to get a set of current URLs for the
resource and an appropriate one can then be selected. Since the cost
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of using the level 2 service is probably greater than the cost of
simply resolving a URL, both the URN and the URL are cached to
provide speedy access unless something has moved.
4.5 Using the architecture to provide interoperability between services
In the simplest sense, each interaction that we have with an
information delivery service does one of two things: it either causes
a pointer to be resolved (a file to be retrieved, a telnet session to
be initiated, etc.) or causes some set of the pointers available in
the information service to be selected. At this level, the
architecture outlined above provides the core implementation of
interoperability. Once we have a means of mapping between names and
pointers, and we have a standard method of specifying names and
pointers, the interoperation problem becomes one of simply handing
names and pointers around between systems. Obviously with such a
simplistic interoperability scheme much of the flavor and
functionality of the various systems are lost in transition. But,
given the pointers, a system can either a) present them to the user
with no additional functionality or b) resolve the pointers, examine
the resources, and then run algorithms designed to tie these
resources together into a structure appropriate for the current
service. Let's look at one example (which just happens to be the
easiest to resolve); interoperation between World Wide Web and
Gopher.
Displaying a Gopher screen as a WWW document is trivial with these
pointers. Every Gopher screen is simply a list of menu items with
pointers behind them (we'll ignore the other functionality Gopher
provides for a moment), so is an extremely simple form of a hypertext
document. Consequently with this architecture it is easy to show and
resolve a Gopher screen in WWW. For a WWW to Gopher map, the
simplest method would be that when one accesses a WWW document, all
the pointers associated with links off to other documents are brought
in with the document. Gopher could then resolve the links and read
the first line of each document to provide a Gopher style screen
which contains everything in the WWW document. When a link is
selected, all of the WWW links for the new document are brought in
and the process repeats. Obviously we're losing a lot with the WWW ->
Gopher mapping; some might argue that we are losing everything.
However, this does provide a trivial interoperability capacity, and
one can argue that the 'information content' has been preserved
across the gateway.
In addition, the whole purpose of gatewaying is to provide access to
resources that lie outside the reach of your current client. Since
all resources are identifiable and accessible through layers 2 and 3,
it will be easy to copy resources from one protocol to another since
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all we need to do is to move the pointers and reexpress the
relationships between the pointers in the new paradigm.
4.6 Other techniques for interoperability
One technique for interoperability which has recently received some
serious attention is the technique of creating one client which
speaks the protocols of all the information delivery tools. This
approach has been taken in particular by the UNITE (User's Network
Interface To Everything) group in Europe. This client would sit on
the top level of the architecture in Figure 1. This technique is best
exemplified by the recent work which has gone into Mosaic, a client
which can speak almost all of the major information services
protocols. This technique has a lot of appeal and has enjoyed quite a
bit of success; however, there are several practical difficulties
with this approach which may hinder its successful implementation.
The first difficulty is one that is common to clients in general; the
clients must be constantly updated to reflect changes in the
underlying protocols and to accommodate new protocols. If the
increase in the number of information services is very gradual, or if
the underlying protocols do not change very rapidly, this may not be
an insuperable difficulty. In addition, old clients must have some
way of notifying their user that they are no longer current;
otherwise they will no longer be able to access parts of the
information mesh.
The second problem is one which may prove more difficult. Each of the
currently deployed information services provides information in a
fundamentally different way. In addition, new information services
are likely to use completely new paradigms for the organization and
display of the information they provide. The various clients of these
information services provide vastly different functionality from each
other because the underlying protocols allow different techniques. It
may very well prove impossible to create a single client which allows
access to the full functionality of each of the underlying protocols
while presenting a consistent user interface to the user.
Much of the success of Mosaic and other UNITE tools is due to the
fact that Gopher, WWW, and other tools are still primarily text
based. When new tools are deployed which depend more on visual cues
than textual cues, it may be substantially more difficult to
integrate all these services into a single client.
We will continue to follow this work and may include it in future
revisions of this architecture if it bears fruit.
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RFC 1727 Resource Transponders December 1994
5. Human interactions with the architecture
In this section we will look at how humans might interact with an
information system based on the above architecture.
5.1 Publishing in this architecture
When we speak of publishing in this section, we are referring only to
the limited process of creating a resource on the net, assigning it a
URN, and spreading the information around that we have created a new
resource.
We start with the creation of a resource. Simple enough; a creative
thought, a couple of hours typing, and a few cups of coffee and we
have a new resource. We then wish to assign it a URN. We can talk to
whichever publishing agent we would like; whether it is our own
personal publishing agent or some big organization that provides URN
and announcement services to a large number of authors. Once we have
a URN, we can provide the publishing agent with a URL for our local
copy of the resource and then let it do its thing. Alternatively, we
can attach a transponder to the resource, let it determine a local
URL for the resource, and let it contact the publishing agent and set
up the announcement process. One would expect a publishing agent to
prompt us for some information as to where it should announce our new
resource.
For example, we may just wish a local announcement, so that only
people in our company can get a pointer to the resource. Or we may
wish some sort of global announcement (but it will probably cost us a
bit of money!)
Once the announcement has been made, the publishing agent will be
contacted by a number of pieces of the resource location system. For
example, someone running a WAIS server may decide to add the resource
to their index. So they can retrieve the resource, index it, and add
the indexes to their tables along with a URI - URL combination. Then
when someone uses that WAIS server, it can go off and retrieve the
resource if necessary. Or, the WAIS server could create a local copy
of the resource; if it wished other people to find their local copy
of the resource, it could provide the URI -> URL mapper with a URL
for the local copy. In any case, publication becomes a simple matter.
So, where does this leave the traditional publisher? Well, there are
a number of other functions which the traditional publisher provides
in addition to distribution. There are editorial services, layout and
design, copyright negotiations, marketing, etc. The only part of the
traditional role that this system changes is that of distributing the
resource; this architecture may make it much cheaper for publishers
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RFC 1727 Resource Transponders December 1994
to distribute their wares to a much wider audience.
Although copying of resources would be possible just as it is in
paper format, it might be easier to detect republication of the
resource in this system, and if most people use the original URN for
the resource, there may be a reduced monetary risk to the publisher.
5.2 A librarian role in this architecture
We've been in a number of discussions with librarians over the past
year, and one question that we're frequently asked is "Does Peter
talk this rapidly all the time?". The answer to that question is
"Yes". But another question we are frequently asked is "If all these
electronic resources are going to be created, supplanting books and
journals, what's left for the librarians?". The answer to that is
slightly more complex, but just as straightforward. Librarians have
excelled at obtaining resources, classifying them so that users can
find them, weeding out resources that don't serve their communities,
and helping users navigate the library itself. None of these roles
are supplanted by this architecture. The only differences are that
instead of scanning publisher's announcements for new resources their
users might be interested in, they will have to scan the
announcements on the net. Once they see something interesting, they
can retrieve it (perhaps buying a copy just as they do now), classify
it, set up a navigation system for their classification scheme, show
users how to use it, and provide pointers (or actual copies) of the
resource to their users. The classification and selection processes
in particular are services which will be badly needed on a net with a
million new 'publications' a day, and many will be willing to pay for
this highly value added service.
5.3 Serving the users
This architecture allows users to see the vast collection of
networked resources in ways both familiar and unfamiliar. Bookstores,
record shops, and libraries can all be constructed on top of this
architecture, with a number of different access methods. Specialty
shops and research libraries can be easily built, and then tailored
to a thousand different users. One never need worry that a book has
been checked out, that a CD is out of stock, that a copy of Xenophon
in the original Greek isn't available locally. In fact, a user could
even engage a proxy server to translate resources into forms that her
machine can use, for example to get a text version of a Postscript
document although her local machine has no Postscript viewer, or to
obtain a translation of a sociology paper written in Chinese.
In any case, however the system looks in three, five, or fifty years,
we believe that the vision we've laid out above has the flexibility
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and functionality to start tying everything together without forcing
everyone to use the same access methods or to look at the net the
same way. It allows new views to evolve, new resources to be created
out of old, and for people to move from today to tomorrow with all
the comforts of home but all the excitement of exploring a new world.
6. References
[Berners-Lee 93] Berners-Lee, T., Masinter, L., and M. McCahill,
Editors, "Universal Resource Locators", RFC 1738, CERN, The Xerox
Corporation, University of Minnesota, December 1994.
Deutsch, P., Master's Thesis, June 1992.
Available for anonymous FTP as
<ftp://archives.cc.mcgill.ca/pub/peterd/peterd.thesis>.
[Weider 94a] Weider, C., "Resource Transponders", RFC 1728, Bunyip
Information Systems, December 1994.
[Weider 94b] Weider, C. and P. Deutsch, "Uniform Resource Names",
Work in Progress.
Security Considerations
Security issues are not discussed in this memo.
7. Authors' Addresses
Chris Weider
Bunyip Information Systems, Inc.
2001 S. Huron Parkway #12
Ann Arbor, MI 48104
Phone: +1 313-971-2223
EMail: clw@bunyip.com
Peter Deutsch
Bunyip Information Systems, Inc.
310 Ste. Catherine St. West, Suite 202
Montreal, Quebec, CANADA
Phone: +1 514-875-8611
EMail: peterd@bunyip.com
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