[jira] [Closed] (JENA-815) RDF XML Literals

["Andy Seaborne (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/JENA-815?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Andy Seaborne closed JENA-815.
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> RDF XML Literals
> ----------------
>
>                 Key: JENA-815
>                 URL: https://issues.apache.org/jira/browse/JENA-815
>             Project: Apache Jena
>          Issue Type: Improvement
>          Components: RDF API, RDF/XML
>    Affects Versions: Jena 2.12.1
>            Reporter: Andy Seaborne
>              Labels: Jena3
>             Fix For: Jena 3.0.0
>
>
> As part of Jena3, we can (re)consider the support for RDF XML literals.
> h3. Context
> In Jena2 (and RDF 1.0) they are special (it is the required datatype).
> This is lessen in RDF 1.1.
> There is support for RDF XML Literals through the "well formedness"
> flag carried around by literals is their {{LiteralLabel}}.  It records whether
> the literal is asserting it is valid exclusive canonical XML (i.e. valid RDF XML Literal by RDF 1.0 rules).
> The flag is only relevant for RDF/XML output.
> In the RDF API I found:
> {noformat}
>    Statement.hasWellFormedXML
>    Literal.isWellFormedXML
>    Model.add(s, p, o, flag)
>    Model.createLiteral
> {noformat}
> Except for tests, {{Literal.isWellFormedXML}} is only called from
> the RDF/XML writer (class Unparser) and {{Statement.hasWellFormedXML}} isn't called at all.
> The flag effects whether the RDF/XML writer includes the literal as
> {{parseType='literal'}} and inlines the XML, so you get nicely nested structures, or whether it used {{datatype=rdf:XMLLIteral}} and writes
> the lexical form encoded.
> The flag is set when a literal is created (see {{LiteralLabel.setValue}}).
> h3. Possible changes
> h4. Leave as-is.
> h4. Remove from RDF API, retain in Node.
> # Deprecate for Jena2 the RDF API operations exposing the well-formedness flag.
> # The {{Unparser}} needs to unwrap the node from the literal and test the "XML directly" flag.
> h4. Remove RDF XML Literals as specially handled in Node.
> # Deprecate for Jena2 the RDF API operations exposing the well-formedness flag.
> # At Jena3, remove the well-formed ness flag in Node
> # The {{Unparser}} needs to test a literal before output.
> # Don't set/test in {{LiteralLabel.setValue}}.
> This is cleaner architecturally, but at the expense of parsing at output.
> *Note*
> There is a whole, separate discussion about whether {{Node}} 
> ought to be value-supporting or not (i.e. moved to the RDF API).  
> It should at least be delayed until needed to avoid overhead.
> h3. Examples
> Input (TTL): Legal RDF/XML Literal:
> {noformat}
> :x :property "<a></a>"^^rdf:XMLLiteral .
> {noformat}
> Output:
> {noformat}
>   <rdf:Description rdf:about="http://example/x">
>     <property rdf:parseType="Literal"><a></a></property>
>   </rdf:Description>
> {noformat}
> Input (TTL): Illegal RDF/XML Literal:
> {noformat}
> :x :property "<a>"^^rdf:XMLLiteral .
> {noformat}
> Output:
> {noformat}
> <rdf:Description rdf:about="http://example/x">
>     <property rdf:datatype="http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral"
>     >&lt;a&gt;</property>
> {noformat}



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