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   Re: [xml-dev] Can anyURI be empty?

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Joe Fawcett wrote:
 > I'm having trouble working out from
 > http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#anyURI
 > [shown at bottom of mail]
 > means that anyURI can be an empty string, can someone elucidate?

If it couldn't, it would be wrong. An empty string is a valid URI.

Bob Foster

 > Thanks
 > Joe
 > Definition:
 > 3.2.17 anyURI
 > [Definition:]   anyURI represents a Uniform Resource Identifier Reference
 > (URI). An anyURI value can be absolute or relative, and may have an 
 > fragment identifier (i.e., it may be a URI Reference). This type 
should be
 > used to specify the intention that the value fulfills the role of a 
URI as
 > defined by [RFC 2396], as amended by [RFC 2732].
 > The mapping from anyURI values to URIs is as defined in Section 5.4 
 > Attribute of [XML Linking Language] (see also Section 8 Character 
 > in URI References of [Character Model]). This means that a wide range of
 > internationalized resource identifiers can be specified when an anyURI is
 > called for, and still be understood as URIs per [RFC 2396], as amended by
 > [RFC 2732], where appropriate to identify resources.
 >   NOTE: Each URI scheme imposes specialized syntax rules for URIs in that
 > scheme, including restrictions on the syntax of allowed fragement
 > identifiers. Because it is impractical for processors to check that a 
 > is a context-appropriate URI reference, this specification follows 
the lead
 > of [RFC 2396] (as amended by [RFC 2732]) in this matter: such rules and
 > restrictions are not part of type validity and are not checked by 
 > conforming· processors. Thus in practice the above definition imposes 
 > very modest obligations on ·minimally conforming· processors.
 > Lexical representation
 > The ·lexical space· of anyURI is finite-length character sequences which,
 > when the algorithm defined in Section 5.4 of [XML Linking Language] is
 > applied to them, result in strings which are legal URIs according to [RFC
 > 2396], as amended by [RFC 2732].
 >   NOTE: Spaces are, in principle, allowed in the ·lexical space· of 
 > however, their use is highly discouraged (unless they are encoded by 
 > Constraining facets
 > anyURI has the following ·constraining facets·:
 >   a.. length
 >   b.. minLength
 >   c.. maxLength
 >   d.. pattern
 >   e.. enumeration
 >   f.. whiteSpace
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