Re: N3.js 0.4.0 with TriG / N-Triples / N-Quads compatibility

The "Media Types" information for N3.js could be updated here:
http://www.w3.org/community/rdfjs/wiki/Comparison_of_RDFJS_libraries#Parsing_libraries

On Fri, Jan 2, 2015 at 2:58 AM, Ruben Verborgh <ruben.verborgh@ugent.be>
wrote:

> Dear all,
>
> Yesterday, I released version 0.4.0 of the N3.js library,
> which, in addition to Turtle, now also parses and writes
> N-Triples, and the quad formats TriG and N-Quads.
> This message gives some insight in how it was build.
> Source code at https://github.com/RubenVerborgh/N3.js.
>
>
> RDF 1.1 SERIALIZATIONS INTRODUCTION
>
> If you are not entirely familiar with the RDF 1.1 specifications,
> below is a preview of what the 4 syntaxes look like.
>
> # N-Triples
>   <http://ex.org/#Tom> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <
> http://ex.org/#Cat>.
>   <http://ex.org/#Tom> <http://www.ex.org/#label> "Tom".
>
> # Turtle
>   @prefix ex: <http://ex.org/#>.
>   ex:Tom a ex:Cat;
>            ex:label "Tom".
>
> # N-Quads
>   <http://ex.org/#Tom> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <
> http://ex.org/#Cat> <http://ex.org/cartoons>.
>   <http://ex.org/#Tom> <http://www.ex.org/#label> "Tom" <
> http://ex.org/cartoons>.
>
> # TriG
>   @prefix ex: <http://ex.org/#>.
>   ex:cartoons {
>     ex:Tom a ex:Cat;
>            ex:label "Tom".
>   }
>
> As you can see, N-Triples and Turtle encode triples;
> N-Quads and TriG encode quads, i.e., triples with a graph.
> Also, Turtle is a superset of N-Triples: anything that is valid N-Triples
> is valid Turtle.
> TriG is also a superset of Turtle, and N-Quads is a superset of N-Triples.
> Unfortunately, TriG is not a superset of N-Quads,
> as TriG and N-Quads use different syntaxes to encode graphs.
>
> Every serialization format comes with positive and negative tests
> to verify whether a parser is compatible:
> http://www.w3.org/TR/rdf11-testcases/
>
>
> IMPLEMENTATION IN N3.JS
>
> Version 0.3.0 of N3.js provided a streaming Turtle parser,
> consisting of a lexer component and an actual parser component.
> Lexer and parser have been written exclusively by hand,
> in order to realize the streaming behavior at maximum performance.
> As a result, simply writing 3 new parsers was not a viable option.
> Note that, even though Turtle is a superset of N-Triples,
> a spec-compatible N-Triples parser must reject non-N-Triples documents.
>
> Instead, I opted to write a lexer and parser that recognize
> the (artificial) superset of TriG and N-Quads;
> that is, the entire example document in this message
> can be converted into quads by the parser,
> even though there is no standard that encompasses it.
>
> In order to pass the specification tests,
> I then added restricted modes to the parser for each subset.
> For instance, for both N-Triples and N-Quads,
> the lexer errors for '@prefix' tokens.
> That way, I can maintain one single, fast codebase.
>
> One could of course argue that the N-Triples / N-Quads syntax
> can be lexed and parsed more easily (line by line),
> and thus faster than with such a hybrid parser.
> Yet in my experience, parsing an N-Triples document
> is slower than its Turtle equivalent (if all features are used),
> because Turtle documents simply contain less characters.
> So the speed we could gain by a simple dedicated parser
> is probably lost anyway due to the size difference.
>
>
> WHAT THIS MEANS FOR RDF-JS DEVELOPERS
>
> Until now, the only way to deal with multiple RDF graphs in JavaScript
> was using the JSON-LD format, since Turtle doesn't have quads.
> N3.js 0.4.0 brings direct access to quad-centric formats.
>
>
> Enjoy!
>
> Ruben
>