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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  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:
  1. client requests/server responses to identify the specific

parameters accepted and/or required on input requests

  1. client request/server responses to identify properties to be

returned in the result set

  1. expression of parameterized input query
  1. expression of result sets
  1. 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 ( and
 NetWords (  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:
  1. 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.
  1. 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.
  1. 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.
  1. 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

  1. 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.
  1. 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.
  1. News feeds: The resource is a press article. The common name is the


  1. 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
  1. Titles of books, movies, songs, poems, short stories, plays, or


  1. Place names
  2. Street names
  3. 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
 ( 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, could create a common name namespace of
    book titles and make it freely available to its users.
    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
 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
 Michael Mealling
 Network Solutions
 505 Huntmar Park Drive
 Herndon, VA 22070
 Phone: (770) 935-5492
 Fax: (703) 742-9552
 Nicolas Popp
 RealNames Corporation
 2 Circle Star Way
 San Carlos, CA  94070-1350
 Phone: 1-650-298-5549
 Karen Sollins
 MIT Laboratory for Computer Science
 545 Technology Sq.
 Cambridge, MA 02139
 Phone: +1 617 253 6006

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
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 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]

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