Problem with % in URI

[dwbutler]

I have some TTL data as follows:

@prefix db: <http://dbpedia.org/resource/> .
@prefix dbm: <http://dbpedia.org/meta/> .
@prefix dbo: <http://dbpedia.org/ontology/> .

db:Michael_Jackson dbo:activeYearsEndYear "2009-01-01T00:00:00Z";
   dbo:activeYearsStartYear "1964-01-01T00:00:00Z";
   dbo:artistOf db:%28I_Can%27t_Make_It%29_Another_Day,

etc

I receive the following error when trying to parse this data with RDF::Reader.for(:n3).new(data)

   dbo:artistOf db:%28I_Can%27t_Make_It%29_Another_Day,

-------------------^
Error on line 22 at offset 19: Found '%' when parsing a pathtail. expected  | "!","expression" | "^","expression"
    from /opt/local/lib/ruby/gems/1.8/gems/rdf-n3-0.3.1.1/lib/rdf/n3/reader/parser.rb:35:in `parse'
    from /opt/local/lib/ruby/gems/1.8/gems/rdf-n3-0.3.1.1/lib/rdf/n3/reader.rb:95:in `each_statement'

I originally wrote this data using the same parser.

Any help you can provide would be greatly appreciated!

[dwbutler]

The problem only seems to happen when using prefixes. If I use full URIs, the problem goes away.

<http://dbpedia.org/resource/Michael_Jackson> <http://dbpedia.org/ontology/activeYearsEndYear> "2009-01-01T00:00:00Z";
   <http://dbpedia.org/ontology/activeYearsStartYear> "1964-01-01T00:00:00Z";
   <http://dbpedia.org/ontology/artistOf> <http://dbpedia.org/resource/%28I_Can%27t_Make_It%29_Another_Day>,

[gkellogg]

That's because in N3, QNames have a prescribed form that disallows the %-encoded URI. A QName has a prefix and a local part, both of which must be NCNames. From Namespaces [1], an NCName is composed of the following characters:

[4]     NCName      ::= (Letter | '_') (NCNameChar)*     /* An XML Name, minus the ":" */
[5]     NCNameChar  ::= Letter | Digit | '.' | '-' | '_' | CombiningChar | Extender

None of these include '%'.

The bug is in the serializer, which does not ensure that an attempt to shorten a URI to a QName ensures that the result is a valid QName. Note that RDFa uses CURIes, instead of QName, and this would be a valid CURIE. I'll update the serializer for N3 (and for RDF/XML) to do this. This should result in the following:

    @prefix db: <http://dbpedia.org/resource/> .
    @prefix dbm: <http://dbpedia.org/meta/> .
    @prefix dbo: <http://dbpedia.org/ontology/> .

    db:Michael_Jackson dbo:activeYearsEndYear "2009-01-01T00:00:00Z";
      dbo:activeYearsStartYear "1964-01-01T00:00:00Z";
      dbo:artistOf <http://dbpedia.org/resource/%28I_Can%27t_Make_It%29_Another_Day> .

[1] http://www.w3.org/TR/1999/REC-xml-names-19990114/#dt-NSDecl

[dwbutler]

Thanks for the quick response! I am not too familiar with the details of the standards, as you can see. :)

I've been experimenting a bit, and found another workaround for this. If you specify the base_uri instead of a prefix, reading and writing work without errors.

BASE_URI = URI.new("http://dbpedia.org/resource/")
repository.dump(:n3, {:prefixes => PREFIXES, :base_uri => BASE_URI})

results in:

@base <http://dbpedia.org/resource/> .
@prefix dbo: <http://dbpedia.org/ontology/> .

<Michael_Jackson> dbo:activeYearsEndYear "2009-01-01T00:00:00Z";
   dbo:activeYearsStartYear "1964-01-01T00:00:00Z";
   dbo:artistOf <%28I_Can%27t_Make_It%29_Another_Day>,

[dannybtran]

Ran into a similar issue when trying to parse data from dbpedia.org.

http://dbpedia.org/data/S'ym.n3

In the last statement on the page, the local portion of the qname contains a single-quote. No doubt, caused by the serializer on dbpedia's end. Nevertheless, it is quite frustrating.