Things get written under Design Issues when I have expressed them several times in various contexts. This idea hit that criterion in a W3C staff meeting in October 2000, as I had suggested it in various contexts and various times, including backstage to Ether Dyson at the Harvard Internet Society conference.

Persistent Domains - Strawman ideas on Web Architecture

Up to Design Issues.

Persistent Domains

This is a proposal to address the problems with the persistence of HTTP URIs. It introduces the concept of a datestamped domain name with associated rights and obligations of ownership.


 The problems of the lack of persistence of URIs lead to many well-known problems, including

 A second-order symptom of the problem is that there is a constant stream of proposals for new URI schemes with different, incompatible, name-lookup technology. These are often made with less attention to the real social issues surrounding persistence than HTTP/DNS, but propose to be systems otherwise similar except in having greater persistence.

The analysis

The persistence of HTTP URIs can be factored into two issues:

  1. The persistence of the opaque string which follows the domain name, and
  2. the persistence of the domain name  itself.

The first of these is an issues is of course under the control of the domain owner.  This, combined with a dearth of tools which help one run a web server with persistent URIs, has led to a vastly varying level of persistence.  Some sites understand and construct their URIs carefully, while some obviously have not thought about the problem and end up changing URIs out of thoughtlessness rather than malice. I have summarized some aspects of this problem in "Cool URIs Don't Change" .  This relies on publishers making an institutional commitment to persistence.  I have tried to lead the way with W3C's draft Persistence Policy. However, this only addresses the first element.

The second issue is summarized by ICANN chair Ester Dyson's line, You don't buy domain names, you rent them. This single meme instantly undermines any public expectation that domain names should be persistent. In principle, if  http://www.example.com/downloads today points to example.com's download page, tomorrow, it could point to anything as defined by a company which has bought, acquired though law suit or accidental expiry the domain name "example.com".   In fact, however, huge numbers of links are being made with HTTP. The planet's investment in domain names in references is huge. The technology which actually is involved in dereferencing such identifiers has become more and more sophisticated.  In practice, also, the legal weight  behind a significant organization's ownership of a domain name is considerable.  No one would dream that a legal battle microsoft.com or ietf.org would be lost to some sneaky entrepreneur.  Through the rift between trademark law and domain names is a problem, there in fact is strong legal support for an organization's ability to keep its name. But is this enough?

The Solution

I think we can do better. We can do better, if this scheme works out, on both issues.  To tackle the second, we can create domain names which are allocated once and once only, which are bought, not rented. We can simultaneously set expectations that such data will endure, that names will not be reused, and that information will be available even after organizations involved have disappeared.  The trick is the same one as used in W3C's datespace URIs (such as http://www.w3.org/2000/01/sw) and British car registration plates: to date code them. For example, let us create a series of top-level persistent domains y2000, y2001 and so on. One would only be able to acquire a .y2000 domain name  during the year 2000. Once acquired one would have it forever. In fact, the domain name would correspond forever to the information published in it. 

We could take the precaution of inserting a few rules for sanity here.  There should be some combination of due diligence to ensure you are not infringing trademark when applying for an alphanumeric name. I would like to put a limit on the number of persistent domains any company could own - or at least put those who have n in the queue ahead of those who have k<n.  There could be a convention that if you are happy with a random numeric domain 6872364.y2000 you can have one immediately and automatically.  It would be great to put some constraint on sitting on a domain without using it, and maybe on transfer of domain ownership.

To tackle the first issue, an organization wishing to enter the scheme makes necessarily a few commitments. One is that it must partake in some cooperating mirroring scheme in which other organizations or commercial services take on running mirrors of the site.  I can imagining this working, for example, as a for-pay service for consumers, or a mirror-ring system for academic institutes. There must be some form of contract which, in the event of the original publisher of the information coming to a voluntary or involuntary demise, the mirror sites will continue the service.  The documents then enter an archive state in which the original publisher loses authority to evolve the domain and the public gain rights of access. The actual contractual arrangements will in fact have to be skillfully set up. For example, there will be some information which will be just so uninteresting that no one will be prepared to pay for it in the long run, but there must be some way to give serious archival institutions (the major national libraries for example) the right to take over an archive for the public good.  However, it would be best to start with simple conditions, but allow them to be modified with experience (real and imagined - gedanken) of the system.  Other interesting things which come to mind include the mirroring of confidential access controlled documents with a 30 year timeout on the confidentiality.

I don't know how best to enforce that a URI is never reallocated to something else by a publisher. Actually, I don't think it will be a long term problem, as the tools will be made such that it is not a function. ("Rename: command not known"!).  Obviously re-use would cause a big mess, as caches across the globe would run out of sync, and assumptions made by mirrors and proxies would become invalid.  Perhaps a suitable disposition for a domain whose publisher consistently flaunts the rules would be for it to be more or less automatically declared dead, and for it to pass into archive state just as though the organization had passed away. The organization can then ask for a new domain and start again - at least the first time.

A clarification of what re-using a URI means.  As I have pointed out many times, most URIs are Generic URIs. They refer to, not a fixed set of bits, but a conceptual resource whose representation may vary with (for example) time, technology, language, and so on.  This is fine, even in a persistent domain. It is in my opinion important to distinguish (and ideally independently identify with separate URIs) generic resources and any specific representation in use in a specific case.  The contractual obligations of ownership of a persistent domain could usefully include the provision of such metadata, and the allocation of a persistent URI to the actual (mime-type, octet-string) specific entity.

Obligations of persistence would have to apply across the transfer of the persistent domain. The persistent domain would be property, with (like land) rights and obligations. Transfer of the domain name would carry within it both.  Fleet Bank would not be able to buy BankBoston and simply drop support for documents bankboston.y2000 - without all public documents falling into archive state.

Another clarification.  A document in archive state has a certain general license to mirror and reproduce in unmutilated form, but the intellectual property rights remain as ever with the author. A very tempting rule (which I am not convinced of yet) is that once the original domain owner has defaulted on publishing the material, that it acquires some limited redistribution license*.  This is the Web equivalent of an implicit right to photocopy any book out of print: the publisher has deigned not to make copies, and it impedes the operation of society to prevent this erstwhile public information from being accessible.


Here is a collection of simplified rules which would form the protocol of persistent domains.

  1. Domain names *.y2000 only allocated in 2000, and so on;
  2. Some level of trademark due diligence before registration for alpha numeric names
  3. Random numeric names   123678.y2000 issued immediately but not transferable
  4. A limit on the number of persistent domain per organization would be useful
  5. Domain names owned for life and persist forever
  6. URIs may be live or frozen but not reused arbitrarily
  7. Implicit irrevocable license for 3rd parties to mirror public info now and after death
  8. The registry(-ar - whatever is the controlling authority, I forget the terminology) would be a neutral non-profit cooperative.
  9. ICANN's delegation of .y[1-9]* would be irrevocable in all time.
  10. Anyone using it would pay me $1 (just kidding! :-)

Provided these are put together with sufficient care, the system should run itself in such a way as to preserve our information world for posterity, be it represented by a consumer in a decade searching for instructions from the now-defunct manufacturer of an appliance, or by a historian in a millennium trying to figure out what on earth made us all tick way back then.


Tim Berners-Lee

First Written: 2000/10/04



Out of Print Books

Joseph Reagle points out a passage in [University System of Georgia] Regents Guide to Understanding Copyright and Educational Fair Use which explains:

4. Out-of-Print-Book SCENARIO D: A library has a book that is out of print and unavailable. The book is an important one in the professor's field that she needs for her research. QUESTION a: May the professor copy the book for her files? ANSWER: Yes. This is another example of personal use. If one engages in the fair use analysis, one finds that: (1) the purpose of the use is educational versus commercial; (2) the professor is using the book, a creative work, for research purposes; (3) copying the entire book would normally exceed the bounds of fair use, however, since the book is out of print and no longer available from any other source, the copying is acceptable; (4) finally, the copying will have no impact on the market for the book because the book is no longer available from any other source. QUESTION b: Using the same facts as explained in SCENARIO D, could the professor copy the book and place the book on reserve in the library? Could the professor scan the book into her computer and place the book onto the World Wide Web? ANSWER: If the professor placed the book on reserve in the library, the use would be considered a fair use. However, if the professor placed the book on the Web, then the use is not a fair use. Placement on the Web allows unlimited access to the book. This would affect the copyright holder's public distribution of the book. See SCENARIO R, SCENARIO T, and SCENARIO U.

Joseph points out that the courts would not necessarily accept a parallel between Web and paper distrbution. My purpose in drawing a parallel was to explain the intent, not to suggest that either action was in fact admissable under any particular jurisdiction.

Note for readers after 2100

Note for readers after 2100.  To understand this document you must first understand the situation which pertained at the dawn of M3. The anarchic chaos which reigned over the embryonic Web is often hard for students to grasp, and the fact that today's Web grew from these chaotic beginnings is a constant marvel. The reader would do well to consult McKinley's "Chaos and Fortune:Civilization from the Robber Barons to Domain Sharks" [Time-Microsoft-Murdock, 2057] for a simple sketch, and Deaton and Plim's "Social Anthropology of the pre-fusion Human" [UNArchivePress, 2068] for a more detailed analysis.