(Last Updated 25 April 2006)

Namespace ID:
urn-6

Registration Information:

Version: 2
Date: 2006-03-18

Declared registrant of the namespace:

Name: Evan Prodromou
E-mail: evan at wikitravel.org
Affiliation: Wikitravel
Address: 1481 rue Rachel E
Montreal QC H2J 2K3
Canada

Declaration of syntactic structure:

The structure of identifiers will be as follows:

urn:<assigned number>:<language code>:place:<place name>
urn:<assigned number>:<language code>:user:<user name>
urn:<assigned number>:<language code>:subject:<topic identifier>

Here, <assigned number> is the number to be assigned. <language code> is
is a 2- or 3-letter ISO 639 language code. In the unlikely event that
a Wikitravel language version is started with a language not coded for
ISO 639, the language code will be a 4- or 5-letter code, beginning with
"x-", followed by 2 or 3 letters not used by ISO 639 and unique within this
URN scheme.

<place name> is the name of a place, in the language defined, with
boundaries as defined in the text and metadata of the corresponding
Wikitravel article. Place names can contain any printable UTF-8 character
except #<>[]|{} . Spaces are encoded as underscores ("_"), and the entire
UTF-8 string is URI encoded. The resultant encoded string has
a maximum size of 255 bytes.

<user name> is the login name of a Wikitravel user, with identical
restrictions and encoding as place names.

<topic identifier> is the name of a topic or subject with identical
restrictions and encoding as place names.

<place name>, <user name> and <topic identifier> are otherwise opaque.

Relevant ancillary documentation:

Wikitravel is a project to create an Open Content travel guide, using
the wiki technique to enable collaboration by travellers worldwide. 
Along with text, photos, and maps, the project also provides 
machine-readable metadata about content, places, and people in
Resource Definition Framework (RDF) format.

URLs for Wikitravel pages or images are used to identify each page
and image, but URNs are used to represent people, places,
and subjects. As 2006-03-02, an experimental URN namespace, "x-wikitravel",
is used.

For example, "http://wikitravel.org/en/Southern_California";
identifies the Wikitravel guide to Southern California in English and
is used for description of the guide (e.g., version numbers, parts of
the guide, contributor credits, date of creation, number of words). 
"urn:<assigned number>:en:place:Southern_California" is used to identify and
describe that area itself (e.g., population, area, cities and counties
contained, containing state, average temperature).

There is a one-to-one equivalence between travel guides and places, such
that "http://wikitravel.org/<language code>/<title>" is the URL for a
travel guide about the place identified by
"urn:<assigned number>:<language code>:place:<title>". The boundaries of the
place are defined by the editors of the travel guide, with
reference to geographical thesauruses, gazetteers, as well as common usage.
A place identified by a Wikitravel URN may or may not have an identifier
in a more formal system such as ISO 3166 or UN/LOCODE. Restrictions on use
of other identification systems for places make them inappropriate for 
an Open Content travel guide.

Similarly, Wikitravel users, who create and edit Wikitravel guides, are
identified with a user URN. Each user has a "home page", but we distinguish
a person from his or her home page to allow descriptions of both (e.g., a
user is author of his or her own home page).

Unstructured topics or "tags" are used to associate places with ideas,
activities, practices, foods, and other subjects that are difficult to
identify formally. For example, <urn:<assigned number>:en:place:Hawaii>
may be associated with "urn:<assigned number>:en:topic:surfing" and
"urn:<assigned number>:en:topic:beaches".

Wikitravel has 9 language versions at present, and several new versions
upcoming. Each language version has a distinct user database, page
database, and topic database. Some may be equivalent across languages;
for example, the person identified by "urn:<assigned number>:en:user:Evan"
is identical to the person "urn:<assigned number>:pt:user:Evan".
However, this is not necessarily the case.

Places may have equivalents, such as "urn:<assigned number>:en:place:Greece"
and "urn:<assigned number>:de:place:Griechenland". Often, these are legally-
defined countries, regions, and urban areas. On the other hand, some places
may not, and may represent local or cultural priorities of the language
community. 

Restrictions on place name are identical to MediaWiki restrictions on
page names.

http://meta.wikimedia.org/wiki/Help:Page_name

Wikitravel page names follow different rules depending on the
language version of Wikitravel, but most are adapted from the
English rules:

http://wikitravel.org/en/Wikitravel:Article_naming_conventions

Identifier uniqueness considerations:

Identifiers for users will be unique in that a user name is
assigned to a single person at account creation time and never
re-used.

Identifiers for topics will be unique in that they encompass all the
nuances of the natural-language words used for the identifiers. For
example, "urn:<assigned number>:en:subject:park" may be used for
city, state and national parks. Although one could say this is a single
identifier for multiple resources, it's more reasonable to consider
it a single identifier for one resource (the overall idea of a park) with
multiple facets (all the different kinds of parks).

Identifiers for places will be unique in that each place will be
associated with a single page, and page names are unique in the wiki
database. The geographic boundaries of a place may change with time,
as legal boundaries change (e.g., the partition of a country, region
or city), or editor agreement about "fuzzy" regions change (e.g.,
is Death Valley part of Southern California, or not? Is Poland in
Central Europe or Eastern Europe?). It may be more reasonable to
consider "Southern California" as a concept, or a space-time event,
rather than a geometric area on the surface of a sphere.

At any one time, a single place identifier will not refer
to two places. In cases where two places have the same name,
disambiguating text is added to the name to clarify which place is
referred to. For example, Paris, France is referred to as
"urn:<assigned number>:en:place:Paris", while Paris, Texas is referred
to as "urn:<assigned number>:en:place:Paris_%28Texas%29", the encoded
value of "Paris (Texas)".

Identifier persistence considerations:

Wikitravel guides are Open Content and freely redistributable under the
terms of the Creative Commons Attribution-ShareAlike 1.0 license
(http://creativecommons.org/licenses/by-sa/1.0/). The guides, individually
and as a collection, have been copied and distributed in electronic and
hardcopy form. The namespace of places, contributors and topics persists
past the existence of wikitravel.org as a domain name and as a wiki.

In other words, the definition of "urn:<assigned number>:en:place:Paris" 
as "the place described in the Wikitravel English-language guide to Paris"
is persistent as long as such a guide exists.

Process of identifier assignment:

Identifiers are assigned by the editors of Wikitravel. This loose group
has open membership.

Process for identifier resolution:

This namespace is not intended for global resolution. However, it is possible
to convert each URN into an URL for a page describing the resource identified
by that URN by the following lexical rules:

urn:<assigned number>:<language code>:place:<place name> ->
http://wikitravel.org/<language code>/<place name>

urn:<assigned number>:<language code>:user:<user name> ->
http://wikitravel.org/<language code>/User:<user name>

urn:<assigned number>:<language code>:subject:<topic identifier> ->
http://wikitravel.org/<language code>/Special:Tag/<topic identifier>

Rules for Lexical Equivalence:

Two identifiers in this namespace are equivalent if:

* the language code is identical
* the sub-namespace ("place", "user", "subject") is identical
* the <place name>, <user name>, or <topic identifier> differ only
in the case of their first character.

For example, "urn:<assigned number>:fr:place:Chine" and 
"urn:<assigned number>:fr:place:chine" are equivalent.

Conformance with URN Syntax:

There should be no problem with URN syntax conformance.

Validation mechanism:

For "place" URNs, the URN is valid if a corresponding page on
Wikitravel exists.

"user" and "subject" URNs cannot be validated.

Scope:

These identifiers are limited in usefulness to wikitravel.org users
and readers and publishers of derived versions of the guides. Some other
communities may benefit from using the "place" identifiers for other
purposes, as a standard URI format for real-world places does not
yet exist. However, the arbitrary meaning of the identifier may make it
less useful for other communities or projects.

(File Created 25 April 2006)
