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openRDF.org Forum » Sesame & Rio: Help » Thread: XML/RDF parsing bug with empty literals.

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Mar 31, 2005 6:25:36 PM

yonasj
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Canada
Joined: Dec 20, 2004
Posts: 38
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XML/RDF parsing bug with empty literals.

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Hello,

I have found a bug in the RDF parsing. Here is a sample file that triggers the bug.


<?xml version="1.0"?>
<rdf:RDF
    xmlns="http://www.maketechnologies.com/BREW/UseCase#"
    xmlns:dcterms="http://purl.org/dc/terms/"
    xmlns:j.0="http://protege.stanford.edu/plugins/owl/protege#"
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema#"
    xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
    xmlns:owl="http://www.w3.org/2002/07/owl#"
    xmlns:xsa="http://www.maketechnologies.com/BREW/XSA.owl#"
    xmlns:cpas="http://brew/Domain-CPAS#"
    xmlns:daml="http://www.daml.org/2001/03/daml+oil#"
    xmlns:dc="http://purl.org/dc/elements/1.1/"
    xmlns:his="http://brew/Domain-HIS#"
  xml:base="http://www.maketechnologies.com/BREW/UseCase">

<xsa:StepList rdf:ID="RoyalState_Individual_810">
	<xsa:Step_step_number rdf:datatype="http://www.w3.org/2001/XMLSchema#string"
	></xsa:Step_step_number>
	<xsa:Step_step_number rdf:datatype="http://www.w3.org/2001/XMLSchema#string"
	>Correct</xsa:Step_step_number>
</xsa:StepList>

</rdf:RDF>

After loading this RDF into a memory repositroy using Sesame 1.1.2 an incorrect statement is created.

The correct statement is:

RoyalState_Individual_810 Step_step_number "Correct"^^http://www.w3.org/2001/XMLSchema#string

The incorrect statement is:
RoyalState_Individual_810 Step_step_number _:node0

Here a BNode is being created.

The BNode has one statement about it. That statement is:

_:node0 rdf:type http://www.w3.org/2001/XMLSchema#string

I beleive that the correct behaviour would be to create a statement where the value is a 0 length string...

Yonas.

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Mar 31, 2005 7:15:11 PM

yonasj
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Canada
Joined: Dec 20, 2004
Posts: 38
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Re: XML/RDF parsing bug with empty literals.

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BTW: You will need to disable validation.

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Apr 1, 2005 9:05:42 AM

arjohn
OpenRDF project lead

The Netherlands
Joined: Jan 23, 2004
Posts: 1289
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Re: XML/RDF parsing bug with empty literals.

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The W3C RDF Validation Service accepts this data as legal RDF. I'll look into it.
----------------------------------------
Arjohn Kampman, OpenRDF project lead, Aduna

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Apr 1, 2005 2:02:16 PM

arjohn
OpenRDF project lead

The Netherlands
Joined: Jan 23, 2004
Posts: 1289
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Re: XML/RDF parsing bug with empty literals.

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It looks like Sesame's parser is right according to a spec, but I find this very strange. Probably, this is an error in the RDF/XML specification. I'll contact the editors of the spec to find out what is the right thing to do.
----------------------------------------
Arjohn Kampman, OpenRDF project lead, Aduna

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Apr 4, 2005 10:11:21 PM

uSeRNaMe
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Joined: Dec 23, 2004
Posts: 2
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Re: XML/RDF parsing bug with empty literals.

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I have experienced this problem as well; it seems that Protege produces RDF like yonasj has posted.

I've modified the RdfXmlParser class to accomodate this:


private void _processPropertyElt(String namespaceURI, String localName, String qName, Atts atts, boolean isEmptyElt)
		throws SAXException
	{
...
        // parseType == null
	else if (isEmptyElt) {
	            
            Att datatype = atts.getAtt(RDF.NAMESPACE, "datatype");
            
            // empty element without an rdf:parseType attribute
	    if (atts.size() == 0) {
		// element had no attributes, or only the optional rdf:ID
		NodeElement subject = (NodeElement)_peekStack(1);
		Literal lit = _createLiteral("", _xmlLang, null);
		_reportStatement(subject.getResource(), propURI, lit);
		_handleReification(lit);
	     }
	     else if( atts.size() == 1 && datatype != null ){
                
                NodeElement subject = (NodeElement)_peekStack(1);
                Literal lit = _createLiteral("", _xmlLang, datatype.getValue());
                _reportStatement(subject.getResource(), propURI, lit);
                _handleReification(lit);
            }

            else {
...
}

I believe this fix is spec-compliant and solves this issue.

Please find the source attached in full.
----------------------------------------

RdfXmlParser.java (39344 bytes) (Download Count: 24) (RdfXmlParser.java - support for empty literals with rdf:datatype defined)

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Apr 5, 2005 10:49:43 AM

arjohn
OpenRDF project lead

The Netherlands
Joined: Jan 23, 2004
Posts: 1289
Status: Offline

Re: XML/RDF parsing bug with empty literals.

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Issue has been logged as [RIO-14]. Error in the specification has been reported on the www-rdf-comments mailing list: http://lists.w3.org/Archives/Public/www-rdf-comments/2005AprJun/0000.html
----------------------------------------
Arjohn Kampman, OpenRDF project lead, Aduna

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Apr 5, 2005 1:44:03 PM

arjohn
OpenRDF project lead

The Netherlands
Joined: Jan 23, 2004
Posts: 1289
Status: Offline

Re: XML/RDF parsing bug with empty literals.

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A fix for this issue is included in Sesame 1.1.3 and Rio 1.0.3, which have just been uploaded to sourceforge.net.

@uSeRNaMe: thanks for the code. I checked in a slightly modified version of the code to fix this issue.
----------------------------------------
Arjohn Kampman, OpenRDF project lead, Aduna

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