Don't auto detect N3 format, as it's too easily confused with Turtle.

lib/rdf/n3/format.rb

@@ -22,31 +22,6 @@ class Format < RDF::Format
 
     reader { RDF::N3::Reader }
     writer { RDF::N3::Writer }
-
-    ##
-    # Sample detection to see if it matches N3 (or N-Triples or Turtle)
-    #
-    # Use a text sample to detect the format of an input file. Sub-classes implement
-    # a matcher sufficient to detect probably format matches, including disambiguating
-    # between other similar formats.
-    #
-    # @param [String] sample Beginning several bytes (~ 1K) of input.
-    # @return [Boolean]
-    def self.detect(sample)
-      !!sample.match(%r(
-        (?:@(base|prefix|keywords)) |                                   # N3 keywords
-        "{3} |                                                          # Multi-line quotes
-        "[^"]*"^^ | "[^"]*"@ |                                          # Typed/Language literals
-        (?:
-          (?:\s*(?:(?:<[^>]*>) | (?:\w*:\w+) | (?:"[^"]*"))\s*[,;]) ||
-          (?:\s*(?:(?:<[^>]*>) | (?:\w*:\w+) | (?:"[^"]*"))){3}
-        )
-      )mx) && !(
-        sample.match(%r(<(?:\/|html|rdf))i) ||                          # HTML, RDF/XML
-        sample.match(%r(^(?:\s*<[^>]*>){4}.*\.\s*$)) ||                 # N-Quads
-        sample.match(%r("@(context|subject|iri)"))                      # JSON-LD
-      )
-    end
   end
 
   # Alias for N3 format

spec/format_spec.rb

@@ -29,8 +29,8 @@
       :n3             => "@prefix foo: <bar> .\nfoo:bar = {<a> <b> <c>} .",
       :default_prefix => ':a :b :c .',
     }.each do |sym, str|
-      it "detects #{sym}" do
-        @format_class.for {str}.should == @format_class
+      it "does not detect #{sym}" do
+        expect(@format_class.for {str}).not_to eq @format_class
       end
     end
 
@@ -53,8 +53,8 @@
       :n3             => "@prefix foo: <bar> .\nfoo:bar = {<a> <b> <c>} .",
       :default_prefix => ':a :b :c .',
     }.each do |sym, str|
-      it "detects #{sym}" do
-        @format_class.detect(str).should be_true
+      it "does not detect #{sym}" do
+        expect(@format_class.detect(str)).not_to be_true
       end
     end