[dotNetRDF-develop] NullReferenceException in RdfaParser

[Broekstra, J. <jee...@wu...>]

Hi there,

I have just started trying out DotNetRDF, and sofar am very impressed. Great work!

However, I have ran into a problem. I am trying to use the RdfaParser in a simple test project, but get a NullReferenceException:

System.NullReferenceException was unhandled
  Message="Object reference not set to an instance of an object."
  Source="dotNetRDF"
  StackTrace:
       at VDS.RDF.Triple..ctor(INode subj, INode pred, INode obj)
       at VDS.RDF.Parsing.RdfAParser.ProcessElement(RdfAParserContext context, RdfAEvaluationContext evalContext, HtmlNode currElement)
       at VDS.RDF.Parsing.RdfAParser.ProcessElement(RdfAParserContext context, RdfAEvaluationContext evalContext, HtmlNode currElement)
       at VDS.RDF.Parsing.RdfAParser.ProcessElement(RdfAParserContext context, RdfAEvaluationContext evalContext, HtmlNode currElement)
       at VDS.RDF.Parsing.RdfAParser.ProcessElement(RdfAParserContext context, RdfAEvaluationContext evalContext, HtmlNode currElement)
       at VDS.RDF.Parsing.RdfAParser.ProcessElement(RdfAParserContext context, RdfAEvaluationContext evalContext, HtmlNode currElement)
       at VDS.RDF.Parsing.RdfAParser.ProcessElement(RdfAParserContext context, RdfAEvaluationContext evalContext, HtmlNode currElement)
       at VDS.RDF.Parsing.RdfAParser.ProcessElement(RdfAParserContext context, RdfAEvaluationContext evalContext, HtmlNode currElement)
       at VDS.RDF.Parsing.RdfAParser.ProcessElement(RdfAParserContext context, RdfAEvaluationContext evalContext, HtmlNode currElement)
       at VDS.RDF.Parsing.RdfAParser.ProcessElement(RdfAParserContext context, RdfAEvaluationContext evalContext, HtmlNode currElement)
       at VDS.RDF.Parsing.RdfAParser.Parse(RdfAParserContext context)
       at VDS.RDF.Parsing.RdfAParser.Load(IGraph g, StreamReader input)
       at DotNetRDFTest.Program.Main(String[] args) in D:\Documents\Visual Studio 2008\Projects\DotNetRDFTest\Program.cs:line 24

The code I am executing is quite simple:

	Graph g = new Graph();
	RdfAParser parser = new RdfAParser();

	StreamReader reader = new StreamReader(WebRequest.Create("http://www.wurvoc.org/vocabularies/om-1.6/Kelvin_scale").GetResponse().GetResponseStream());

			
	parser.Load(g, reader);

The exception occurs on the parser.Load. 

It may be that the RDFa document I am parsing contains syntax errors (I've generated it myself, but I'm still struggling a bit with the exact RDFa syntax). Regardless, it seems to me that the parser should handle unexpected content more gracefully than with a NRE :)

Is this a bug in the parser, or am I doing something wrong in invoking it?

Cheers,

Jeen

PS using DotNetRDF 0.2.2 alpha and .Net 3.5. Also included a ref to the HtmlAgilityPack.
-- 
dr. J. Broekstra
Wageningen UR, Food & Biobased Research
Intelligent Systems group
P.O. Box 17, 6700 AA Wageningen
Wageningen Campus, Building 118, Bornse Weilanden 9, 6708 WG Wageningen
Tel. +31 (0)317 480145
http://www.fbresearch.nl/InformationManagement