* constraint: The identification mechanism for the Web is
the URI.

      * constraint: Web architecture does not constrain a Web
resource to be identified by a single URI.

      * practice: Resource owners should not create arbitrarily
different URIs for the same resource.

      * practice: If a URI has been assigned to a resource,
agents SHOULD refer to the resource using the same URI, character
for character.

      * practice: Avoid URI ambiguity.

      * practice: Authors of specifications SHOULD NOT introduce
a new URI scheme when an existing scheme provides the desired
properties of identifiers and their relation to resources.

      * practice: Agents making use of URIs MUST NOT attempt to
infer properties of the referenced resource except as licensed by
relevant specifications.

      * practice: A resource owner who creates a URI with a
fragment identifier and who uses content negotiation to serve
multiple representations of the identified resource SHOULD NOT
serve representations with inconsistent fragment identifier
semantics.

      * practice: Publishers of a URI SHOULD provide
representations of the identified resource consistently and
predictably.

      * practice: Publishers of a URI SHOULD provide
representations of the identified resource.

      * practice: Format designers SHOULD provide for version
information in language instances.

      * practice: Format designers SHOULD document change
policies for XML namespaces.

      * practice: Language designers SHOULD provide mechanisms
that allow any party to create extensions that do not interfere
with conformance to the original specification.

      * practice: Language designers SHOULD specify agent
behavior in the face of unrecognized extensions.

      * practice: Language designers SHOULD design formats that
allow authors to separate content from presentation and interaction
concerns.

      * practice: Language designers SHOULD provide mechanisms
for identifying links to other resources and to portions of
representation data (via fragment identifiers).

      * practice: Language designers SHOULD provide mechanisms
that allow Web-wide linking, not just internal document
linking.

      * practice: Language designers SHOULD allow authors to use
URIs without constraining them to a limited set of URI schemes.

      * practice: Language designers SHOULD incorporate hypertext
links into a data format if hypertext is the expected user
interface paradigm.

      * practice: Language designers who create new XML
vocabularies SHOULD place all element names and global attribute
names in a namespace.

      * practice: Resource owners who publish an XML namespace
name SHOULD make available material intended for people to read and
material optimized for software agents in order to meet the needs
of those who will use the namespace vocabulary.

      * practice: Specifications that use QNames to represent
URI/local-name pairs SHOULD NOT allow both forms in attribute
values or element content where they would be indistinguishable
from URIs.

      * practice: Language designers who use QNames as
identifiers of Web resources MUST provide a mapping to URIs.

      * practice: In general, server managers SHOULD NOT assign
Internet Media Types beginning with "text/" to XML
representations.

      * practice: In general, server managers SHOULD NOT specify
the character encoding for XML data in protocol headers since the
data is self-describing.

      * principle: Silent recovery from error is harmful.

      * principle: A resource owner SHOULD assign a URI to each
resource that others will expect to refer to.

      * principle: User agents MUST NOT silently ignore
authoritative server metadata.

      * principle: Agents do not incur obligations by retrieving
a representation.