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Network Working Group                                            N. PoppRequest for Comments: 2972                         RealNames CorporationCategory: Informational                                      M. Mealling                                                       Network Solutions                                                             L. Masinter                                                               AT&T Labs                                                              K. Sollins                                                                     MIT                                                            October 2000Context and Goals for Common Name ResolutionStatus 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.Abstract   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   <http://lists.internic.net/archives/cnrp-ietf.html>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 reasonablePopp, 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 viaPopp, 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 conditionsPopp, 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   descriptions.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 insection 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 andPopp, 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     headline.   - Vertical directories: the DNS TLD categories, the ISO country     codes.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   are:   - Titles of books, movies, songs, poems, short stories, plays, or     compilations   - Place names   - Street names   - People's namesPopp, 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   scope.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, ...).  APopp, 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   (http://www.microsoft.com/windows/Ie/Features/AutoSearch/default.asp)   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   prerequisite.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 commonPopp, 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      name)      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 20009. Authors' Addresses   Larry Masinter   AT&T Labs   75 Willow Road   Menlo Park, CA 94025   Phone: +1 650 463 7059   EMail: LMM@acm.orghttp://larry.masinter.net   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.eduPopp, et al.                 Informational                     [Page 10]

RFC 2972       Context & Goals for Common Name Resolution   October 200010. 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   English.   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   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Popp, et al.                 Informational                     [Page 11]