Proposal

OK folks,

In the interests of satisfying all interested parties,
I offer the following proposal for an alternative
solution to the present one, based on nothing new,
just a partial roll back to a more traditional M&S
treatment of XML literals.

Changes:

1. The datatype rdf:XMLLiteral is discarded.

2. The attribute+value rdf:parseType="Literal" is
strictly syntactic, indicating a plain literal
which is serialized in the RDF/XML instance as XML.
I.e. a literal constituting text with markup.

3. The attribute rdf:datatype can co-occur with
rdf:parseType="Literal". The combination of these two
together is similar to the present interpretation of
rdf:parseType="Literal" alone, but now requires the
explicit specification of a datatype rather than
being implicitly taken to be of type rdf:XMLLiteral.

--

Thus, given a context of

   <rdf:RDF ... xml:lang="fi">
      ...
   </rdf:RDF>

all of the following:

1. <rdf:Description rdf:about="#x">
      <ex:foo>bar</ex:foo>
   </rdf:Description>

2. <rdf:Description rdf:about="#x">
      <ex:foo rdf:parseType="Literal">bar</ex:foo>
   </rdf:Description>

3. <rdf:Description rdf:about="#x" ex:foo="bar"/>

generate the same triple:

  <#x> ex:foo "bar"@fi .

--

All of the following:

4. <rdf:Description rdf:about="#x">
      <ex:foo rdf:parseType="Literal"><xhtml:b>bar</xhtml:b></ex:foo>
   </rdf:Description>

5. <rdf:Description rdf:about="#x">
      <ex:foo>&lt;xhtml:b&gt;bar&lt;/xhtml:b&gt;</ex:foo>
   </rdf:Description>

6. <rdf:Description rdf:about="#x" ex:foo="&lt;xhtml:b&gt;bar&lt;/xhtml:b&gt;"/>

generate the same triple:

   <#x> ex:foo "<xhtml:b>bar</xhtml:b>"@fi .

--

Both of the following:

7. <rdf:Description rdf:about="#x">
      <ex:foo rdf:datatype="&ex;blargh">bar</ex:foo>
   </rdf:Description>

8. <rdf:Description rdf:about="#x">
      <ex:foo rdf:datatype="&ex;blargh" rdf:parseType="Literal">bar</ex:foo>
   </rdf:Description>

generate the same triple:

   <#x> ex:foo "bar"^^ex:blargh .

--

And both of the following:

9. <rdf:Description rdf:about="#x">
      <ex:foo rdf:datatype="&ex;blargh" rdf:parseType="Literal"><xhtml:b>bar</xhtml:b></ex:foo>
   </rdf:Description>

10.<rdf:Description rdf:about="#x">
      <ex:foo rdf:datatype="&ex;blargh">&lt;xhtml:b&gt;bar&lt;/xhtml:b&gt;</ex:foo>
   </rdf:Description>

generate the same triple:

   <#x> ex:foo "<xhtml:b>bar</xhtml:b>"^^ex:blargh .

--

Users are then free to choose between legacy M&S literals, with lang
tag, with no special distinction made in the graph regarding the
presence or absence of markup; or alternatively, typed literals
with no lang tags and likewise no distinction made in the graph regarding
the presence or absence of markup in the lexical forms.

There remains no semantic distinction between a plain literal and
an XML literal. An "XML literal" is simply a plain literal with
XML markup that is serialized as unescaped XML. Nothing more.

RDF continues to have two kinds of literals, plain and typed, and 
comparison of plain literals, regardless of the presence of markup, 
is by simple string comparison. All reference to canonicalization 
is removed from the specs -- hopefully moved to a Note addressing the 
use of RDF with datatyped literals having XML encoded lexical forms,
and including the definition of a datatype equivalent to rdf:XMLLiteral
or a similar interpretation of xsd:complexType.

Let the market and user community decide which alternative,
plain or typed literal, is best for which application.

Equivalences between plain literals and typed literals is
left to each individual specification of each datatype.

Note again, that this alternative proposal introduces nothing
substantively new to the mix. And in fact, the minor changes
to the RDF/XML syntax represent how most earlier RDF parsers
treated rdf:parseType="Literal" to begin with.

It also will allow folks to say useful things like

   <rdf:Description rdf:about="#x">
      <ex:foo rdf:datatype="&xhtml;b" rdf:parseType="Literal">
         <xhtml:b>bar</xhtml:b>
      </ex:foo>
   </rdf:Description>

i.e.

   <#foo> ex:foo "<xhtml:b>bar</xhtml:b>"^^xhtml:b .

and thus take advantage of being able to serialize those typed
XML encoded lexical forms without escaping.

--

Martin, does that meet your expectations and wishes
better than the present solution? 

If so, is the WG favorable to such a proposed change?

Regards,

Patrick

--
Patrick Stickler
Nokia, Finland
patrick.stickler@nokia.com

Received on Thursday, 10 July 2003 11:02:32 UTC