diff --git a/doc/TODO b/doc/TODO
index 8a8dcf53..ebc469ad 100644
--- a/doc/TODO
+++ b/doc/TODO
@@ -1,6 +1,13 @@
 todo:
 - expressions should be class-based, and joins too, anything _sql should be renamed
 - refactor adapter pattern
+- clean up block_given stuff
+- reorganize sql tests
+- audit unit coverage of algebra
+- break out adapters into sep modules
+- data objects
+- remove all explicit aliasing
+- blocks for joins
 - implement in memory adapter
 - implement mnesia adapter
 - joins become subselects in writes:
@@ -11,10 +18,8 @@ users.delete().where(
     ) 
 - rename externalize to derived.
 - and/or w/ predicates
-- blocks for all operations
 - result sets to attr correlation too
 - cache expiry on write
-  - rewrite of arecord querycache test in light of this
 - transactions
 - scoped writes
 - asc/desc for orderings
@@ -83,6 +88,7 @@ done:
 - rename select to where
 - rename all ion classes
 - joining with LIMIT is like aggregations!!
+- blocks for non-joins
 
 icebox:
 - #bind in Attribute and Expression should be doing a descend?
diff --git a/lib/arel/algebra/primitives/attribute.rb b/lib/arel/algebra/primitives/attribute.rb
index 5e216770..943c5b03 100644
--- a/lib/arel/algebra/primitives/attribute.rb
+++ b/lib/arel/algebra/primitives/attribute.rb
@@ -109,23 +109,23 @@ def in(array)
 
     module Expressions
       def count(distinct = false)
-        distinct ?  Expression.new(self, "DISTINCT").count :  Expression.new(self, "COUNT")
+        distinct ?  Distinct.new(self).count :  Count.new(self)
       end
 
       def sum
-        Expression.new(self, "SUM")
+        Sum.new(self)
       end
 
       def maximum
-        Expression.new(self, "MAX")
+        Maximum.new(self)
       end
 
       def minimum
-        Expression.new(self, "MIN")
+        Minimum.new(self)
       end
 
       def average
-        Expression.new(self, "AVG")
+        Average.new(self)
       end
     end
     include Expressions
diff --git a/lib/arel/algebra/primitives/expression.rb b/lib/arel/algebra/primitives/expression.rb
index b67a5e1f..98939772 100644
--- a/lib/arel/algebra/primitives/expression.rb
+++ b/lib/arel/algebra/primitives/expression.rb
@@ -1,12 +1,12 @@
 module Arel
   class Expression < Attribute
-    attributes :attribute, :function_sql, :alias, :ancestor
+    attributes :attribute, :alias, :ancestor
     deriving :==
     delegate :relation, :to => :attribute
     alias_method :name, :alias
 
-    def initialize(attribute, function_sql, aliaz = nil, ancestor = nil)
-      @attribute, @function_sql, @alias, @ancestor = attribute, function_sql, aliaz, ancestor
+    def initialize(attribute, aliaz = nil, ancestor = nil)
+      @attribute, @alias, @ancestor = attribute, aliaz, ancestor
     end
 
     def aggregation?
@@ -15,11 +15,11 @@ def aggregation?
 
     module Transformations
       def as(aliaz)
-        Expression.new(attribute, function_sql, aliaz, self)
+        self.class.new(attribute, aliaz, self)
       end
 
       def bind(new_relation)
-        new_relation == relation ? self : Expression.new(attribute.bind(new_relation), function_sql, @alias, self)
+        new_relation == relation ? self : self.class.new(attribute.bind(new_relation), @alias, self)
       end
 
       def to_attribute
@@ -28,4 +28,12 @@ def to_attribute
     end
     include Transformations
   end
+
+  class Count    < Expression; end
+  class Distinct < Expression; end
+  class Sum      < Expression; end
+  class Maximum  < Expression; end
+  class Minimum  < Expression; end
+  class Average  < Expression; end
 end
+
diff --git a/lib/arel/engines/sql/primitives.rb b/lib/arel/engines/sql/primitives.rb
index 5544d637..c4968558 100644
--- a/lib/arel/engines/sql/primitives.rb
+++ b/lib/arel/engines/sql/primitives.rb
@@ -13,12 +13,6 @@ def to_sql(formatter = Sql::WhereCondition.new(relation))
     end
   end
 
-  class Expression < Attribute
-    def to_sql(formatter = Sql::SelectClause.new(relation))
-      formatter.expression self
-    end
-  end
-
   class Value
     def to_sql(formatter = Sql::WhereCondition.new(relation))
       formatter.value value
@@ -28,4 +22,34 @@ def format(object)
       object.to_sql(Sql::Value.new(relation))
     end
   end
+  
+  class Expression < Attribute
+    def to_sql(formatter = Sql::SelectClause.new(relation))
+      formatter.expression self
+    end
+  end
+  
+  class Count < Expression
+    def function_sql; 'COUNT' end
+  end
+  
+  class Distinct < Expression
+    def function_sql; 'DISTINCT' end
+  end
+  
+  class Sum < Expression
+    def function_sql; 'SUM' end
+  end
+  
+  class Maximum < Expression
+    def function_sql; 'MAX' end
+  end
+  
+  class Minimum < Expression
+    def function_sql; 'MIN' end
+  end
+  
+  class Average < Expression
+    def function_sql; 'AVG' end
+  end
 end
\ No newline at end of file
diff --git a/spec/arel/unit/primitives/attribute_spec.rb b/spec/arel/unit/primitives/attribute_spec.rb
index 6d0f146a..e512b40e 100644
--- a/spec/arel/unit/primitives/attribute_spec.rb
+++ b/spec/arel/unit/primitives/attribute_spec.rb
@@ -139,31 +139,31 @@ module Arel
 
       describe '#count' do
         it "manufactures a count Expression" do
-          @attribute.count.should == Expression.new(@attribute, "COUNT")
+          @attribute.count.should == Count.new(@attribute)
         end
       end
 
       describe '#sum' do
         it "manufactures a sum Expression" do
-          @attribute.sum.should == Expression.new(@attribute, "SUM")
+          @attribute.sum.should == Sum.new(@attribute)
         end
       end
 
       describe '#maximum' do
         it "manufactures a maximum Expression" do
-          @attribute.maximum.should == Expression.new(@attribute, "MAX")
+          @attribute.maximum.should == Maximum.new(@attribute)
         end
       end
 
       describe '#minimum' do
         it "manufactures a minimum Expression" do
-          @attribute.minimum.should == Expression.new(@attribute, "MIN")
+          @attribute.minimum.should == Minimum.new(@attribute)
         end
       end
 
       describe '#average' do
         it "manufactures an average Expression" do
-          @attribute.average.should == Expression.new(@attribute, "AVG")
+          @attribute.average.should == Average.new(@attribute)
         end
       end
     end
diff --git a/spec/arel/unit/primitives/expression_spec.rb b/spec/arel/unit/primitives/expression_spec.rb
index ebde55ff..92f300c4 100644
--- a/spec/arel/unit/primitives/expression_spec.rb
+++ b/spec/arel/unit/primitives/expression_spec.rb
@@ -9,13 +9,13 @@ module Arel
 
     describe Expression::Transformations do
       before do
-        @expression = Expression.new(@attribute, "COUNT")
+        @expression = Count.new(@attribute)
       end
 
       describe '#bind' do
         it "manufactures an attribute with a rebound relation and self as the ancestor" do
           derived_relation = @relation.where(@relation[:id].eq(1))
-          @expression.bind(derived_relation).should == Expression.new(@attribute.bind(derived_relation), "COUNT", nil, @expression)
+          @expression.bind(derived_relation).should == Count.new(@attribute.bind(derived_relation), nil, @expression)
         end
 
         it "returns self if the substituting to the same relation" do
@@ -25,7 +25,7 @@ module Arel
 
       describe '#as' do
         it "manufactures an aliased expression" do
-          @expression.as(:alias).should == Expression.new(@attribute, "COUNT", :alias, @expression)
+          @expression.as(:alias).should == Expression.new(@attribute, :alias, @expression)
         end
       end
 
@@ -38,7 +38,7 @@ module Arel
 
     describe '#to_sql' do
       it "manufactures sql with the expression and alias" do
-        sql = Expression.new(@attribute, "COUNT", :alias).to_sql
+        sql = Count.new(@attribute, :alias).to_sql
 
         adapter_is :mysql do
           sql.should be_like(%Q{COUNT(`users`.`id`) AS `alias`})