RE: Questions about value expansion

Hi Sean,

Now to your second mail :-)

On Friday, November 07, 2014 2:08 PM, Sean Johnson wrote:
> I'm curious about the value expansion implementation in the Ruby 
> library, jsonld.

Gregg is implementer of that library, but I'll do my best to answer your questions.



> In particular, the expanding of native types. Here's some tests from the 
> library:

In general, you should have a look at our test suite [1-2] which expresses all of this in a language-indented manner.. if you submit an implementation report, we'll include your conformance level in the official conformance report [3].


>        "native boolean" => ["foo", true,                           
> {"@value" => true}],
>        "native integer" => ["foo", 1,                              
> {"@value" => 1}],
>        "native double" =>  ["foo", 1.1e1,                          
> {"@value" => 1.1E1}],
>        "native date" =>    ["foo", Date.parse("2011-12-27"),       
> {"@value" => "2011-12-27", "@type" => RDF::XSD.date.to_s}],
>        "native time" =>    ["foo", Time.parse("10:11:12Z"),        
> {"@value" => "10:11:12Z", "@type" => RDF::XSD.time.to_s}],
>        "native dateTime" =>["foo", 
> DateTime.parse("2011-12-27T10:11:12Z"), {"@value" => 
> "2011-12-27T10:11:12Z", "@type" => RDF::XSD.dateTime.to_s}],
> 
> Why does a native date, time and dateTime get expanded to include an 
> @type, but a native integer does not?

Honestly, I have no clue... and it's difficult to figure out what's going on here since you cite this without any context.

> That seems inconsistent. And why 
> does the @type get added in this case when the spec doesn't mention 
> adding @type unless the active context includes a type mapping?

When converting from or to RDF, types sometimes get added. See

   http://www.w3.org/TR/json-ld-api/#data-round-tripping

for all details (this is obviously also expressed in the algorithms handling this).

> http://www.w3.org/TR/json-ld-api/#value-expansion

Value expansion is not one of those though :-)


> Similarly, I don't understand this value expansion behavior:
> 
>      %w(boolean integer string dateTime date time).each do |dt|
>        it "expands datatype xsd:#{dt}" do
>          expect(subject.expand_value("foo", RDF::XSD[dt])).to 
> produce({"@id" => "http://www.w3.org/2001/XMLSchema##{dt}"}, @debug)
>        end
>      end
> 
> If I'm translating the Ruby correctly, it's if the value is literally a 
> Ruby type, then expand it to an IRI pointing to the W3C XML Schema IRI 
> for the type. Again… I don't see any mention of that in the value 
> expansion portion of the spec:
> 
> http://www.w3.org/TR/json-ld-api/#value-expansion

Again, I don't know what's going on here and I don't have the time to dig into that. I would suggest to not try to reverse-engineer one of the existing implementations (that might do more than what's required) but really implement the algorithms as specified and run the official test suite.


> Thanks for the help! I'm just trying to ensure I do the right thing with 
> value expansion and I'm confused by these differences in the spec and 
> the Ruby implementation.

Then simply ignore the Ruby implementation :-) The spec is hopefully clear enough.. if not, let us know. Many more people will be able to help you with that than figuring out what a snippet of a specific implementation is doing (especially without context or links to the code).


Cheers,
Markus


[1] https://github.com/json-ld/json-ld.org/tree/master/test-suite
[2] http://json-ld.org/test-suite/
[3] http://json-ld.org/test-suite/reports/


--
Markus Lanthaler
@markuslanthaler

Received on Wednesday, 12 November 2014 22:35:14 UTC