Internet DRAFT - draft-hardie-vac-req
HTTP/1.1 200 OK
Date: Tue, 09 Apr 2002 00:17:32 GMT
Server: Apache/1.3.20 (Unix)
Last-Modified: Sat, 02 Mar 1996 13:58:01 GMT
INTERNET-DRAFT E. Hardie
Expires April, 1996 NASA/NAIC
Requirements and Scenarios for a Voluntary Access Control System
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its
areas, and its working groups. Note that other groups may also
distribute working documents as Internet-Drafts. Distribution of
this memo is unlimited.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use
Internet-Drafts as reference material or to cite them other than
as ``work in progress.''
To learn the current status of any Internet-Draft, please check
the "1id-abstracts.txt" listing contained in the Internet-Drafts
Shadow Directories on ds.internic.net (US East Coast),
nic.nordu.net (Europe), ftp.isi.edu (US West Coast), or
munnari.oz.au (Pacific Rim).
This document specifies the requirements and fundamental scenarios
for a Voluntary Access Control system, based on the content rating
of Internet resources and subsequent filtering of which resources
may be accessed.
The availability on the Internet of a variety resources, intended
for many different audiences, causes concern to some members of
the Internet community and to other members of the societies in
which the Internet is found. This concern suggests the
development of a method for creating and transmitting content
information for Internet resources, so that users may create
filters which eliminate material they would find offensive or
In this document, the requirements are set out for a voluntary
access control system. It is presumed that such a system will
be composed of several interlocking elements. One element of
that system will be a label format for content information.
A second element will be a transport method or methods for
supplying that content information. A third element will be
a set of rules applied to the content information in order to
filter access. Requirements for the third element are described in
this document only functionally. Examples within this draft may
refer to particular content ratings or rule sets, but these should
not be taken as labels or rules which must be implemented for
conformance. A very small number of labels may be reserved by
VAC authors, but it is the intent of the author of this draft
that any system built according to the requirements described here
be both extensible and entirely value-neutral.
Interactive Internet Resources:
Internet resources in which a user chooses to participate in an
interaction, with or without knowledge of the other participants.
Examples include mailing lists to which users subscribe and chat
systems such as IRC.
This word, or the adjective "optional", means that this item is
one of an allowed set of alternatives. An implementation which
does not include this option MUST be prepared to interoperate with
another implementation which does include the option.
This word, or the adjective "required", means that the definition is
an absolute requirement of the specification.
This phrase means that the definition is an absolute prohibition of
This word, or the adjective "recommended", means that there may
exist valid reasons in particular circumstances to ignore this
item, but the full implications must be understood and carefully
weighed before choosing a different course.
A complete VAC action, consisting of a request from the client
and a response from the server.
User-retrieved Internet Resources:
Internet resources or information collections made available by
an information provider through protocols in which a user initiates
the retrieval of items from the collection. Examples of user
initiated processes include ftp, gopher, and http.
A VAC system must be able to handle labels applied to user-retrieved
Internet Resources. A VAC system may choose to apply labels to
Interactive Internet Resources.
2.1 An adult wishes to limit a child's access to the material on
the Internet, eliminating all access to all material having certain
2.2 Teachers wish to use structured browsing as a learning
activity and would like to limit student access to Internet
resources that have been identified as appropriate to particular
2.3 A browser user wishes to reduce time wasted in exploring
sites which are low-quality and would like to have prior knowledge
of which sites have been designated as well-designed or interesting.
2.4 A trainer whishes to demonstrate the usefulness of the
Internet to a group of novice users and would like to eliminate
access to material having certain characteristics and to highlight
material which has been designated as well-designed or interesting.
3. Scenario Implications
The scenarios listed above can be described as enabling a user
to create virtual "blacklists", "whitelists", and "goldlists". In
2.1, the user wishes to create a virtual blacklist, eliminating all
access to certain materials, but leaving open access to all other
materials. In 2.2, the reverse occurs; the user wishes to designate
certain materials as appropriate and eliminate access to all other
materials, thus creating a virtual whitelist. In 2.3, the user may
access any material, but will prefer certain materials which have
been placed on a virtual goldlist. In 2.4, a blacklist and goldlist
are used in combination to create a particular view of Internet
The goals of the four users in the scenarios above could be
accomplished through actual lists. Goldlists (usually described as
"cool sites" or "hot lists"), in particular, have been a part of the
World Wide Web almost since its inception. Creating,
maintaining, and transmitting these lists is, however, inefficient,
and the lists easily become out of date. A Voluntary Access Control
system can accomplish the same goals as each of these list types
through interaction of a rule set and a label.
4. Label format requirements
4.1 The label format must be unambiguous. Labels must always be
made up of the same number of parts which occur in the same order.
4.2 Label format must be applicable at multiple levels of granularity.
For user-retrieved internet resources, this means that the label format
must support ratings for collections as well as resources.
4.3 Labels must be unordered. If a client wishes to request content
information embodied in several labels, the order of the label
request or label response must not affect the labels' interpretation.
4.4 Labels should be human-readable. In order to make goldlists
possible and to allow the user to understand the cause of any
blacklisting, the client must be able to display the label to a user
for interpretation. This may be accomplished by transmitting a
non-human readable short form if the server is certain that the
client can translate it into a human readable form.
4.5 Labels should allow the easy application of rule sets. Where
numeric label characteristics can be used, they should be preferred;
where numeric ranges are used, a specific range order (ascending or
descending) should be established as a default.
4.6 Labels should allow the application of complex rule sets.
Non-numeric and non-range numeric labels must be allowed for label
characteristics, in order to allow for the application of rule sets
which cannot be easily written as numeric range boundaries.
4.7 Certain labels should be reserved to preserve interoperability
among implementations. Labels for date-rated, rating-originator,
and a request for all the ratings available for a particular document
or resource are among those which should be standardized.
5. Transport requirements.
5.1 The VAC transport protocol must be lightweight. A successful
VAC transaction should take place within a single network round
5.2 The VAC transport protocol should allow for persistent
connections. Since some clients will browse through pages at a
rapid rate, polling the same set of servers each time, persistent
connections will help improve performance.
5.3 In accordance with a layered network model, VAC should be
implementable over a variety of connection schemes and underlying
transport protocols; it is expected however, that it will initially
be transported over TCP.
5.4 The VAC transport protocol must support proxying.
5.5 Where proxies are used, VAC should distinguish between proxies
which cache the ratings of other servers and proxies which
themselves filter sites which may be accessed. Where proxies are
used as filter points, progress messages should indicate clearly
that the proxy has prevented access to a resource when such an
6. Rule sets requirements
6.1 Rule set syntax must support statements of inclusion,
exclusion, and display. To accomplish the goals set out in 2.1,
for example, the rule set would exclude all sites which are
labeled as having content the adult believes is inappropriate for
that child. In 2.2, the rule set will include only sites which
the teachers have labeled as appropriate to the lesson. In 2.3,
the labels for particular sites or objects would be displayed
along with the links to the objects, so that the user may choose
those which appeal most. In 2.4, a rule of exclusion is applied
prior to displaying labels for available objects. More complex
rule sets are, of course, possible and encouraged.
7. Authentication requirements
7.1 VAC must support the authentication of the label server to the
client. Given that ratings servers will likely be subject to
attempts at spoofing, authentication of the server to the client
7.2 VAC should support the authentication of the client to the
server. Since some ratings services will be commercial
enterprises, client authentication should be supported.
7.3 VAC should be compatible with multiple mechanisms for
authentication, in order to accommodate variable site policies and
the vagaries of encryption regulations.
8. Intellectual property requirements
8.1 VAC may allow encryption of the rating. Since commercial
enterprises will invest time and capital in the creation of labels,
encryption may be necessary to protect this intellectual capital.
When available, VAC should use Internet-standard methods for session
encryption and authentication. Until such methods are standard, VAC
may allow a client and server to encrypt the rating, using methods
agreed on in out-of-band negotiations.
The author would like to acknowledge the useful discussions of
members of the firstname.lastname@example.org mailing list and the
attendees of the IETF "Read the Label" BOF at the Stockholm
As noted in sections 7 and 8 above.
Edward Hardie -- email@example.com
Network Applications and Information Center
NASA Ames Research Center
Mail Stop 204-14
Moffett Field, CA 94035-1000