adding first node

lib/arel.rb

 require 'arel/version'
 require 'arel/table'
 require 'arel/attributes'
+require 'arel/nodes'
 
 # below is deprecated
 require 'arel/sql/engine'

lib/arel/attributes/attribute.rb

 module Arel
   module Attributes
     class Attribute < Struct.new :relation, :name, :column
+      def eq other
+        Nodes::Equality.new self, other
+      end
     end
 
-    class String < Attribute; end
-    class Time < Attribute; end
+    class String  < Attribute; end
+    class Time    < Attribute; end
     class Boolean < Attribute; end
     class Decimal < Attribute; end
-    class Float < Attribute; end
+    class Float   < Attribute; end
     class Integer < Attribute; end
   end
 end

lib/arel/nodes.rb

+require 'arel/nodes/equality'

lib/arel/nodes/equality.rb

+module Arel
+  module Nodes
+    class Equality
+      attr_accessor :left, :right
+
+      def initialize left, right
+        @left  = left
+        @right = right
+      end
+    end
+  end
+end

spec/arel/attributes/attribute_spec.rb

+require 'spec_helper'
+
+module Arel
+  module Attributes
+    describe 'attribute' do
+      describe '#eq' do
+        it 'should return an equality node' do
+          attribute = Attribute.new nil, nil, nil
+          equality = attribute.eq 1
+          equality.left.should == attribute
+          equality.right.should == 1
+          equality.should be_kind_of Nodes::Equality
+        end
+      end
+    end
+  end
+end