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This Finding addresses the question of whether or not adding new names to a (published) namespace is a sound practice.
This document has been produced for review by the W3C Technical Architecture Group (TAG). This finding addresses TAG issue nameSpaceState-48.
This document is an editor's draft without any normative standing.
Additional TAG findings, both accepted and in draft state, may also be available.
The terms MUST, SHOULD, and SHOULD NOT are used in this document in accordance with [RFC 2119].
Please send comments on this finding to the publicly archived TAG mailing list www-tag@w3.org (archive).
Namespaces are a mechanism for managing names in a distributed way that greatly reduces the likelihood that two independent parties will create the same name for different resources.
The terms in a namespace are two-part identifiers consisting of a namespace name, a URI, and a local name (an NCName as defined in [XML Namespaces]). Using a URI leverages the well-understood URI allocation mechanisms of [WebArch Vol 1].
The proposed definition of a new local name “id
” in
the xml:
namespace raised a question about the identity
of a namespace. Concretely, one perspective was that the
xml:
namespace consisted of xml:space
,
xml:lang
, and xml:base
(and no other names)
because there was a point in time in which those where the only three
names from that namespace that had a defined meaning. Another
perspective was that the xml:
namespace consisted of all
possible local names and that only a finite (but flexible) number of
them are defined at any given point in time.
The publication of [xml:id] as a
Recommendation,
provides a partial answer to the question of which perspective is
correct. Adding the local name “id
” to the
xml:
namespace demonstrates that the xml:
namespace evolves according to the latter position.
The question remains, however, as to whether the former position is ever sound. This Finding takes the position that it is.
Namespaces, originally designed to provide names for XML elements and attributes, have been adopted much more broadly by the web community. They are now used not simply for elements and attributes but for function names, tokens, and identifiers for an ever expanding class of resources.
The xml:
namespace demonstrates that some namespaces
benefit from a policy that allows additional names to be defined in them
over time. This does not seem to preclude the possibility that some
namespaces would benefit from a policy that forbids such extension.
From these observations, we conclude that the following good practice
applies:
Good Practice
Specifications that define namespaces SHOULD explicitly state their policy with respect to changes in the names defined in that namespace. For namespaces that are not immutable, they SHOULD describe how names may be added (or removed) and by whom.