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Re: take 2: primer text for parseType="Literal"

From: Frank Manola <fmanola@mitre.org>
Date: Fri, 25 Jul 2003 08:05:43 -0400
Message-ID: <3F211D17.5010500@mitre.org>
To: Graham Klyne <gk@ninebynine.org>
CC: rdf core <w3c-rdfcore-wg@w3.org>

Graham Klyne wrote:

> 
> This looks good to me.  One tiny nit and one small comment:
> 
> Nit: The use of "third" in "using a third value of the rdf:parseType 
> attribute" seemed a little odd to me.  Maybe just:  'using the attribute 
> rdf:parseType="literal"'?


This may look odd because you don't have the context.  Four paragraphs 
before, in the prior section (on rdf:value), I describe "the second use" 
of rdf:parseType, rdf:parseType="Resource".  Two sections before that, 
the section on Collections introduces rdf:parseType (and notes that it 
has multiple values), in the process of introducing the first use, 
rdf:parseType="Collection".  Mentioning the third use was just to gently 
point out that this was something the reader had seen variants of before.


> 
> Comment:  it might help to underscore somehow that using 
> rdf:parseType="literal" doesn't require that the data contain markup.  
> This is implicit and clear to one who has followed this discussion, but 
> I'm not sure how clear that would be to someone coming fresh to this text.
> 
> For example, may the sentence:
> [[
> The value of the property is a typed literal, whose datatype, 
> rdf:XMLLiteral, is defined in [RDF-CONCEPTS] specifically to represent 
> fragments of XML.
> ]]
> 
> might be:
> 
> [[
> The value of the property is a typed literal, whose datatype, 
> rdf:XMLLiteral, is defined in [RDF-CONCEPTS] specifically to represent 
> fragments of XML, including character sequences that may or may not 
> include XML markup.
> ]]
> 


I agree;  this is a useful clarification.

On another issue, since we're clarifying things: in the text below, in 
discussing exclusive canonicalization, the text says:

"This causes declarations of used namspaces to be added to the fragment..."

I wonder if this wouldn't be clearer if it said:

"This causes declarations of *namespaces used in the fragment* to be 
added to the fragment..."

to distinguish namespaces used in the RDF/XML in general from those 
explicitly used in the fragment.

--Frank


> -- 
> 
> At 15:05 24/07/03 -0400, Frank Manola wrote:
> 
>> Based on Brian's last "take", I propose to put the following text in 
>> the Primer for parseType="Literal".  The typed literal given for the 
>> value of <dc:title> in the triple is that produced by the RDF 
>> Validation Service, but someone may want to check this further anyway.
>>
>> 4.5  XML Literals
>>
>> Sometimes the value of a property needs to be a fragment of XML, or 
>> text that might contain XML markup.  For example, a publisher might 
>> maintain RDF metadata that includes the titles of books and articles.  
>> While such titles are often just simple strings of characters, this is 
>> not always the case.  For instance, the titles of books on mathematics 
>> may contain mathematical formulas that could be represented using 
>> MathML [MATHML]. Titles might also include markup for other reasons, 
>> such as for Ruby annotations [RUBY], or for bidirectional rendering or 
>> special glyph variants (see, e.g., [CHARMOD]).
>>
>> RDF/XML provides a special notation to make it easy to write literals 
>> of this kind.  This is done using a third value of the rdf:parseType 
>> attribute.  Giving an element the attribute rdf:parseType="Literal" 
>> indicates that the contents of the element are to be interpreted as an 
>> XML fragment.  Example 22 illustrates the use of rdf:parseType="Literal":
>>
>> <?xml version="1.0"?>
>> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
>>    xmlns:dc="http://purl.org/dc/elements/1.1/"
>>    xml:base="http://www.example.com/books">
>>
>>   <rdf:Description rdf:ID="book12345">
>>     <dc:title rdf:parseType="Literal">
>>        <span xml:lang="en">
>>          The <em>&lt;br /&gt;</em> Element Considered Harmful.
>>        </span>
>>     </dc:title>
>>   </rdf:Description>
>>
>> </rdf:RDF>
>>
>> The RDF/XML in Example 22 describes a graph containing one triple:
>>
>> ex:book12345 <dc:title> "&lt;span xml:lang="en"&gt; The 
>> &lt;em&gt;&lt;br /&gt;&lt;/em&gt; Element Considered Harmful. 
>> &lt;/span&gt;"^^rdf:XMLLiteral .
>>
>> The rdf:parseType="Literal" attribute in the RDF/XML indicates that 
>> all the XML within the <dc:title> element is an XML fragment that is 
>> the value of the dc:title property.
>>
>> The value of the property is a typed literal, whose datatype, 
>> rdf:XMLLiteral, is defined in [RDF-CONCEPTS] specifically to represent 
>> fragments of XML.  The XML fragment is canonicalized according to the 
>> XML Exclusive Canonicalization recommendation [XML-XC14N].  This 
>> causes declarations of used namespaces to be added to the fragment, 
>> the escaping of reserved characters such as '<', '>' and '&', and 
>> possibly, the re-ordering of attributes.  Contextual attributes, such 
>> as xml:lang and xml:base are not inherited from the RDF/XML document, 
>> and, if required, must, as shown in the example, be explicitly 
>> specified in the XML fragment.
>>
>> This example illustrates that care must be taken designing RDF data.  
>> It might appear at first glance that titles are simple strings best 
>> represented as plain literals, and only later might it be discovered 
>> that some titles contain markup.  In cases where the value of a 
>> property may
>> sometimes contain markup and sometimes not, either 
>> rdf:parseType="Literal" should be used throughout, or software must 
>> handle both plain literals and rdf:XMLLiterals as values of this 
>> property.
>>
>> @@Informational References to be added:
>>
>> [RUBY] Ruby Annotations, Sawicki, M., Suignard, M., Ishikawa, M., 
>> Durst, M., Texin, T., World Wide Web Consortium, 31 May 2001.  This 
>> version is http://www.w3.org/TR/2001/REC-ruby-20010531/.  The latest 
>> version is http://www.w3.org/TR/ruby/.
>>
>> [XML-XC14N] @@use citation in Syntax
>>
>> [CHARMOD]  @@use citation in Syntax
>>
>> [MATHML] Mathematical Markup Language (MathML) Version 2.0, Carlisle, 
>> D., Ion, P., Miner, R., Poppelier, N. (Editors); Ausbrooks, R., 
>> Buswell, S., Dalmas, S., Devitt, S., Diaz, A., Hunter, R., Smith, B., 
>> Soiffer, N., Sutor, R., Watt, S. (Principal Authors), World Wide Web 
>> Consortium, 21 February 2001.  This version is 
>> http://www.w3.org/TR/2001/REC-MathML2-20010221.  The latest version is 
>> http://www.w3.org/TR/MathML2.
>>
>>
>>
>>
>> -- 
>> Frank Manola                   The MITRE Corporation
>> 202 Burlington Road, MS A345   Bedford, MA 01730-1420
>> mailto:fmanola@mitre.org       voice: 781-271-8147   FAX: 781-271-875
> 
> 
> -------------------
> Graham Klyne
> <GK@NineByNine.org>
> PGP: 0FAA 69FF C083 000B A2E9  A131 01B9 1C7A DBCA CB5E
> 


-- 
Frank Manola                   The MITRE Corporation
202 Burlington Road, MS A345   Bedford, MA 01730-1420
mailto:fmanola@mitre.org       voice: 781-271-8147   FAX: 781-271-875
Received on Friday, 25 July 2003 07:41:34 EDT

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