Questions about value expansion

Hello,

I'm curious about the value expansion implementation in the Ruby 
library, jsonld.

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

       "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? 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?

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

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

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.

Cheers,
Sean