RFC 2972

Network Working Group                                            N. Popp
Request for Comments: 2972                         RealNames Corporation
Category: Informational                                      M. Mealling
                                                       Network Solutions
                                                             L. Masinter
                                                               AT&T Labs
                                                              K. Sollins
                                                            October 2000

              Context and Goals for Common Name Resolution

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.


   This document establishes the context and goals for a Common Name
   Resolution Protocol.  It defines the terminology used concerning a
   "Common Name" and how one might be "resolved", and establishes the
   distinction between "resolution" and more elaborate search
   mechanisms.  It establishes some expected contexts for use of Common
   Name Resolution, and the criteria for evaluating a successful
   protocol.  It also analyzes the various motivations that would cause
   services to provide Common Name resolution for both public, private
   and commercial use.

   This document is intended as input to the formation of a Common Name
   Resolution Protocol working group.  Please send any comments to
   cnrp-ietf@lists.internic.net.  To review the mail archives, see

1. Introduction

   People often refer to things in the real world by a common name or
   phrase, e.g., a trade name, company name, or a book title.  These
   names are sometimes easier for people to remember and enter than
   URLs; many people consider URLs hard to remember or type.
   Furthermore, because of the limited syntax of URLs, companies and
   individuals are finding that the ones that might be most reasonable

Popp, et al.                 Informational                      [Page 1]

RFC 2972       Context & Goals for Common Name Resolution   October 2000

   for their resources are already being used elsewhere and therefore
   unavailable.  Common names are not URIs (Uniform Resource
   Identifiers) in that they lack the syntactic structure imposed by
   URIs; furthermore, unlike URNs, there is no requirement of uniqueness
   or persistence of the association between a common name and a
   resource.  These common names are expected to be used primarily by
   humans (as opposed to machine agents).

   Common name "resolution" is a process of mapping from common names to
   Internet resources; a Common Name Resolution Protocol (CNRP) is a
   network protocol used in such a process.

   A useful analogy for understanding the purpose and scope of common
   names, and CNRP, are everyday (human language) dictionaries.  These
   cover a given language (namespace) -- perhaps a spoken language, or
   some specific subset (e.g., technical terms, etc).  Some dictionaries
   give definitions, others give translations (e.g., to other
   languages).  Different entities publish dictionaries that cover the
   same language -- e.g., Larousse and Collins can both publish French-
   language dictionaries.  Thus, the dictionary publisher is the analog
   to the resolution service provider -- the service can provide a
   value-add and build up name recognition for itself, but does not
   impede other entities from providing definitions for precisely the
   same strings in the language.

   Services are arising that offer a mapping from common names to
   Internet resources (e.g., as identified by a URI).  These services
   often resolve common name categories such as company names, trade
   names, or common keywords.  Thus, such a resolution service may
   operate in one or a small number of categories or domains, or may
   expect the client to limit the resolution scope to a limited number
   of categories or domains.  For example, the phrase "Internet
   Engineering Task Force" is a common name in the "organization"
   category, as is "Moby Dick" in the book category.  A single common
   name may be associated with different data records, and more than one
   resolution service is expected to exist.  Any common name may be used
   in any resolution service.

   Two classes of clients of such services are being built: browser
   improvements and web accessible front-end services. Browser
   enhancements modify the "open" or "address" field of a browser so
   that a common name can be entered instead of a URL.  Internet search
   sites integrate common name resolution services as a complement to
   search. In both cases, these may be clients of back-end resolution
   services.  In the browser case, the browser must talk to a service
   that will resolve the common name. The search sites are accessed via

Popp, et al.                 Informational                      [Page 2]

RFC 2972       Context & Goals for Common Name Resolution   October 2000

   a browser.  In some cases, the search site may also be the back-end
   resolution service, but in others, the search site is a front-end to
   a collection of back-end services.

   This effort is about the creation of a protocol for client
   applications to communicate with common name resolution services, as
   exemplified in both the browser enhancement and search site
   paradigms.  Although the protocol's primary function is resolution,
   it is intended to address the issues of internationalization,
   authentication and privacy as well.  Name resolution services are not
   generic search services and thus do not need to provide complex
   Boolean query, relevance ranking or similar capabilities.  The
   protocol is expected to be a simple, minimal interoperable core.
   Mechanisms for extension will be provided, so that additional
   capabilities can be added later.

   Several other issues, while of importance to the deployment of common
   name resolution services, are outside of the resolution protocol
   itself and are not in the initial scope of the proposed effort.
   These include discovery and selection of resolution service
   providers, administration of resolution services, name registration,
   name ownership, and methods for creating, identifying or insuring
   unique common names.

2. Key Goals for a Common Name Resolution Protocol

   The key deliverable is a protocol for parameterized resolution.
   "Resolution" is defined as the retrieval of data associated (a
   priori) with descriptors that match the input request.
   "Parameterized" means the ability to have a multi-component
   descriptor both as part of the query and the response.  These
   descriptors are attribute-value pairs.  They are not required to
   provide unique identification, therefore 0 or more records may be
   returned to meet a specific input query.  The protocol will define:

      - client requests/server responses to identify the specific
        parameters accepted and/or required on input requests

      - client request/server responses to identify properties to be
        returned in the result set

      - expression of parameterized input query

      - expression of result sets

      - standard expression of error conditions

Popp, et al.                 Informational                      [Page 3]

RFC 2972       Context & Goals for Common Name Resolution   October 2000

   To avoid creating a general search protocol with unbounded
   complexity, and to keep the protocol simple enough so that different
   implementations will have similar behavior, the resolution protocol
   should be limited to sub-string matches against parameter values.  To
   support full internationalization, UTF-8 encoding of strings and
   sub-strings is preferred.

   In addition, the working group should define one sample service based
   on this protocol -- the resolution of so-called "common names", or
   resolution of non-unique, registered strings to resource

3. CNRP goals

   The goal of CNRP is to create a lightweight search protocol with a
   simple query interface, with a focus on making the common case of
   substring search with a single result most efficient.  In addition,
   efficient support for keyed value search is important.  Each key is a
   named meta property of the resource (e.g. category, language,
   geographical region.).  Some of these properties could be
   standardized (e.g. the common name property).  The goal is to support
   partial specification of query parameters and even partial and fuzzy
   matches on names.  CNRP is intended to be simpler than LDAP for
   simple applications.

   Besides simplicity, the CNRP protocol should be consistent with
   efficient implementation of a simple and intuitive user interface.
   The emphasis on the common name as the common denominator to find a
   wide range of resources reduces the UI to its minimal expression (the
   user types a few words in a text box and presses enter).

   CNRP should provide interoperability with multiple common name
   databases (section 4 presents many examples of such databases).  The
   query interface should be extensible and customizable to the specific
   needs of a specific type of resolution service.  However, the need
   for interoperability across databases and resolution services
   combined with the need to ensure the scalability of search (across
   millions of names from multiple providers) have lead this group to
   consider the explicit requirement of supporting categories in CNRP.
   This requirement is discussed further in section 5.

4. Example of common name namespaces

   Commercial companies have already developed and deployed common name
   resolution services such as RealNames (http://www.realnames.com) and
   NetWords (http://www.netword.com).  These commercial implementations
   are mainly focused on trade names, such as company names, brands and

Popp, et al.                 Informational                      [Page 4]

RFC 2972       Context & Goals for Common Name Resolution   October 2000

   trademarks.  These services constitute a concrete example of common
   name namespaces implementation and are useful to understand the scope
   of the CNRP effort.

   CNRP is also directly targeted at directory service providers. CNRP
   is relevant to these services to increase their reach through
   integration into larger Web sites such as the search portals.  For
   example, IAtlas has developed a directory service for businesses that
   it distributes through its Web site and Inktomi.  IAtlas could
   immediately leverage CNRP to distribute their service through their
   external distribution partners.

   Directory services must not be confused with search engines.
   Directory services use highly structured information to identify a
   resource.  This information is external to the actual resource and is
   called metadata.  In contrast, search engines mainly rely on the
   content of the resource (e.g. the text of a Web page).

   CNRP plays well with directory services that present a critical piece
   of information about the resource in the form of a textual
   identifier, a title or a terse description (the common name).
   Numerous examples come instantly to mind: company names, book titles,
   people names, songs, ISBNs, and social security numbers.  In all
   cases, the common name is the natural property for users to lookup
   the resource.  The common name is always simple and intuitive: it has
   no syntax, it is multilingual, memorable and can often be guessed.

   The following list is intended to put in prospective the wide range
   of applications for CNRP:

   - Business directories (SEC, NASDAQ, E*Trade, .).  The resource is
     company information (address, products, SEC filings, stock quotes,
     etc.).  The common name is the company name.

   - White pages (BigFoot, WhoWhere, Switchboard, ...): The resource a
     person (current address, telephone numbers, email addresses,
     employer, ...).  The common name is a last name, a telephone number
     or an email address.

   - E-commerce directories: The resource is a product for sale (car,
     house, furniture, actually almost any type of consumption item).
     The common name is a brand name or a description.

   - Publishing directories: The resource is one of many things: a book,
     a poem, a CD, an MP3 download.  The common name is an ISBN, a song
     title, an artist's name. The common name is typically the title of
     a publication.

Popp, et al.                 Informational                      [Page 5]

RFC 2972       Context & Goals for Common Name Resolution   October 2000

   - Entertainment directories: The resource is an event (a movie, a
     concert, a TV show).  The common name is the name or a description
     for the event, the movie title, a rock band name, a show.

   - Yellow pages services: Here again, the resource can be very
     diverse: a house for sale, a restaurant, a car dealership or other
     type of establishment or service that can be found in the
     traditional yellow pages.  The common name can be a street address,
     the name of a business, or a description.

   - News feeds: The resource is a press article. The common name is the

   - Vertical directories: the DNS TLD categories, the ISO country

5. Private and public namespaces

   A set of common names within a category (books, news, businesses,
   etc.)  is called a common name "namespace". The term "namespace" only
   refers to the set of names.  It does not encompass the bindings or
   associations between a name and data about the name (such as a
   resource, identified by a URI).  Such bindings might be created and
   maintained by a common name resolution services. Resolution services
   may create binding that are relevant for the type of service that
   they offer.

   It is useful to distinguish between "private" and "public"
   namespaces.  A namespace is private if owned by an authority that
   controls the right to assign the names.  A namespace is private even
   if the right to assign those names is held by a neutral party.

   A namespace is public when not controlled by any single authority or
   resolution provider.  Assignment of the names is distributed.
   However, it is reasonable to expect that people who assign names will
   tend to pick names that have a minimum of collisions.  For some of
   these namespaces, there will even be mechanisms to discourage
   duplicate assignment, but all of them are inherently ambiguous.
   Public namespaces are not controlled. Examples of public namespaces

   - Titles of books, movies, songs, poems, short stories, plays, or
   - Place names
   - Street names
   - People's names

Popp, et al.                 Informational                      [Page 6]

RFC 2972       Context & Goals for Common Name Resolution   October 2000

   Because these namespaces are unbounded and open to any types of name
   assignment, they will have scalability problems.  To support these
   namespaces, CNRP must provide at least one standard mechanism to
   filter a large list of related results.  A filtering mechanism must
   allow the user to narrow the search further down to a smaller result
   set, because the common name alone may not be enough.

   One possible search filter is related to the notion of categories.
   Because categories create a structure to organize named resources,
   large resolution services are likely to support some sort of
   categorization system (whether flat or hierarchical).  Although
   categories constitute an efficient search filter, defining standard
   vocabularies for common name categories is beyond the scope of the
   protocol design.  The protocol design for CNRP should not require a
   standardized taxonomy for categories in order to be effective.  For
   example, CNRP resolution could use free-form keywords; the end-user
   would use these keywords as part of the query.  Each service would
   then be responsible for mapping the keywords to zero, one or many
   categories in their own classification.  The keywords would remain
   classification independent and different services could use different
   categorization schemes without compromising interoperability.  It
   would then be up to the service to provide its own mapping.  For
   example, let us assume that one namespace is resolving names under
   the category: "Hobby & Interests > collecting > antique > books".
   Assume that a second namespace has decided to organize the names of
   similar resources under the classification: "Arts > Humanities >
   Literature > History of Books and Printing > antiques".  Although the
   two taxonomies are different, a CNRP query specifying
   category_keywords = "antique books" would allow each service to
   identify the appropriate category.  This mechanism may ensure that
   the two result lists are small and coherent enough to be merged into
   one unique result set.  It is important to note that this approach
   would work whether the classification is hierarchical or not.

   Although this suggestion has merit, it is fair to say that it remains
   unproven.  In particular, it is unclear that the category_keywords
   property would guarantee full interoperability across resolution
   services.  In any case, free form keywords for specifying categories
   is just one of several possible ways of limiting the scope of a
   query.  Although the specific mechanisms are not agreed upon a this
   time, CNRP will provide at least one standard mechanism for limiting

6. Distributors/integrators of common name resolution services

   We anticipate two main categories of distributors for common
   namespaces.  The first category is made of the Web portals such as
   search engines (Yahoo, MSN, Lycos, Infoseek, AltaVista, ...).  A

Popp, et al.                 Informational                      [Page 7]

RFC 2972       Context & Goals for Common Name Resolution   October 2000

   common name resolution service will typically address only one very
   specialized aspect of search (company names or book titles or people
   names, ..).  This type of focused lookup service is a useful
   complement to generic search.  Hence, portals are likely to integrate
   several types of common name services.  CNRP solves the difficult
   problem of integrating multiple external independent services within
   one Web site.  Today, the lack of standardization in performance
   requirements and query interface leads to loose integration (co-
   branded pages hosted on virtual domains) or maintenance problems
   (periodical data dumps).  CNRP is aimed at solving some of these
   issues. CNRP facilitates the deployment of embedded services by
   creating a common interface to all common name services.

   The second category of distributors is made of the Web browser
   companies. Netscape's smart browsing
   (http://home.netscape.com/communicator/v4.5/index.html#smart) and
   Microsoft's IE5 auto-search features
   demonstrate that the two dominant Web browser companies understand
   the value of navigation and search from the command line of the
   browser.  It is very clear how this command line could be used as the
   main user interface to common name resolution services through CNRP.
   In many ways, it is actually the most natural user interface to
   resolve a common name.  For this strategic component of the browser's
   user interface to remain truly open to all common name resolution
   services, it is key that there exists a standard resolution protocol
   (and a service discovery mechanism).  CNRP will give users access to
   the largest selection of services and providers and the ability to
   select a specific resolution service over another.  To preserve the
   user from proprietary implementations, the existence of CNRP is a

7. Example of cost recovery models for maintenance of namespaces

   The following discussion of possible business models for common name
   namespaces is intended to prove that they are commercially viable,
   hence that CNRP will be used in the market place.  This section
   presents 5 different cost recovery models.

   a. Licensing the lookup service

      In such model, the owner of the database owner licenses the data
      and the resolution service to a portal.  This is a proven model.
      For example, Looksmart (a directory service) recently licensed all
      their data to MSN.  Another possibility is to sell access to the
      service directly to the user.  For some vertical type of common

Popp, et al.                 Informational                      [Page 8]

RFC 2972       Context & Goals for Common Name Resolution   October 2000

      names service (e.g. patent search), it is also conceivable that a
      specific type of users (e.g., lawyers) would be willing to pay for
      accessing a precise resolution service.

   b. Sharing revenue generated by banner advertising

      In this model, the database owner licenses his infrastructure
      (data and resolution service) to a portal.  Prepaid banner ads are
      placed on the result pages.  The revenue is shared between the
      resolution service provider and the portal that hosts the pages.

   c. Selling the names (charge the customer a fee for subscribing a

      This is a proven business model as well (NSI, GOTO, RealNames,
      Netword, for of the name has a large user reach (search engines
      sell keywords for instance).

   d. Value added service

      Another model is to build a common name as a free added value
      service in order to make a core service more compelling to users.
      For example, Amazon.com could create a common name namespace of
      book titles and make it freely available to its users.  Amazon.com
      would not make any money from the resolution service per se.
      However, it would indirectly since the service would help the
      users find hence buy more books from Amazon.com.

   e. "Some-strings-attached" free names

      A namespace may give users a name for free in exchange for
      something else (capturing the user's profile that can be sold to
      merchants, capturing the user's email address in order to send
      advertising emails, etc.).

8. Security and Intellectual Property Rights Considerations

   This document describes the goals of a system for multi-valued
   Internet identifiers.  This document does not discuss resolution;
   thus questions of secure or authenticated resolution mechanisms are
   out of scope.  It does not address means of validating the integrity
   or authenticating the source or provenance of Common Names.  Issues
   regarding intellectual property rights associated with objects
   identified by the various Common Names are also beyond the scope of
   this document, as are questions about rights to the databases that
   might be used to construct resolvers.

Popp, et al.                 Informational                      [Page 9]

RFC 2972       Context & Goals for Common Name Resolution   October 2000

9. Authors' Addresses

   Larry Masinter
   AT&T Labs
   75 Willow Road
   Menlo Park, CA 94025

   Phone: +1 650 463 7059
   EMail: LMM@acm.org

   Michael Mealling
   Network Solutions
   505 Huntmar Park Drive
   Herndon, VA 22070

   Phone: (770) 935-5492
   Fax: (703) 742-9552
   EMail: michaelm@netsol.com

   Nicolas Popp
   RealNames Corporation
   2 Circle Star Way
   San Carlos, CA  94070-1350

   Phone: 1-650-298-5549
   EMail: nico@realnames.com

   Karen Sollins
   MIT Laboratory for Computer Science
   545 Technology Sq.
   Cambridge, MA 02139

   Phone: +1 617 253 6006
   EMail: sollins@lcs.mit.edu

Popp, et al.                 Informational                     [Page 10]

RFC 2972       Context & Goals for Common Name Resolution   October 2000

10. Full Copyright Statement

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an


   Funding for the RFC Editor function is currently provided by the
   Internet Society.

Popp, et al.                 Informational                     [Page 11]