diff --git a/lib/remote_storage/riak.rb b/lib/remote_storage/riak.rb
index cec809c..768de46 100644
--- a/lib/remote_storage/riak.rb
+++ b/lib/remote_storage/riak.rb
@@ -40,8 +40,11 @@ module RemoteStorage
     def get_data(user, directory, key)
       object = data_bucket.get("#{user}:#{directory}:#{key}")
 
+      server.halt 304 if server.env["HTTP_IF_NONE_MATCH"] == object.etag
+
       server.headers["Content-Type"] = object.content_type
       server.headers["Last-Modified"] = last_modified_date_for(object)
+      server.headers["ETag"] = object.etag
 
       if binary_key = object.meta["binary_key"]
         object = cs_binary_bucket.files.get(binary_key[0])
@@ -66,25 +69,34 @@ module RemoteStorage
 
     def get_directory_listing(user, directory)
       directory_object = directory_bucket.get("#{user}:#{directory}")
+
+      server.halt 304 if server.env["HTTP_IF_NONE_MATCH"] == directory_object.etag
+
       timestamp = directory_object.data.to_i
       timestamp /= 1000 if timestamp.to_s.length == 13
       server.headers["Content-Type"] = "application/json"
       server.headers["Last-Modified"] = Time.at(timestamp).to_s(:rfc822)
+      server.headers["ETag"] = directory_object.etag
 
       listing = directory_listing(user, directory)
 
       return listing.to_json
     rescue ::Riak::HTTPFailedRequest
-      server.headers["Content-Type"] = "application/json"
-      return "{}"
+      server.halt 404
     end
 
     def put_data(user, directory, key, data, content_type=nil)
       object = build_data_object(user, directory, key, data, content_type)
 
+      if required_match = server.env["HTTP_IF_MATCH"]
+        server.halt 412 unless required_match == object.etag
+      end
+
       object_exists = !object.raw_data.nil?
       existing_object_size = object_size(object)
 
+      server.halt 412 if object_exists && server.env["HTTP_IF_NONE_MATCH"] == "*"
+
       timestamp = (Time.now.to_f * 1000).to_i
       object.meta["timestamp"] = timestamp
 
@@ -96,13 +108,14 @@ module RemoteStorage
         new_object_size = object.raw_data.size
       end
 
-      response = object.store
+      object.store
 
       log_count = object_exists ? 0 : 1
       log_operation(user, directory, log_count, new_object_size, existing_object_size)
 
       update_all_directory_objects(user, directory, timestamp)
 
+      server.headers["ETag"] = object.etag
       server.halt 200
     rescue ::Riak::HTTPFailedRequest
       server.halt 422
@@ -111,6 +124,11 @@ module RemoteStorage
     def delete_data(user, directory, key)
       object = data_bucket.get("#{user}:#{directory}:#{key}")
       existing_object_size = object_size(object)
+      etag = object.etag
+
+      if required_match = server.env["HTTP_IF_MATCH"]
+        server.halt 412 unless required_match == etag
+      end
 
       if binary_key = object.meta["binary_key"]
         object = cs_binary_bucket.files.get(binary_key[0])
@@ -126,6 +144,7 @@ module RemoteStorage
       timestamp = (Time.now.to_f * 1000).to_i
       delete_or_update_directory_objects(user, directory, timestamp)
 
+      server.headers["ETag"] = etag
       server.halt riak_response[:code]
     rescue ::Riak::HTTPFailedRequest
       server.halt 404
@@ -222,8 +241,9 @@ module RemoteStorage
       sub_directories(user, directory).each do |entry|
         directory_name = entry["name"].split("/").last
         timestamp = entry["timestamp"].to_i
+        etag = entry["etag"]
 
-        listing.merge!({ "#{directory_name}/" => timestamp })
+        listing.merge!({ "#{directory_name}/" => etag })
       end
 
       directory_entries(user, directory).each do |entry|
@@ -233,20 +253,16 @@ module RemoteStorage
                     else
                       DateTime.rfc2822(entry["last_modified"]).to_time.to_i
                     end
+        etag = entry["etag"]
 
-        listing.merge!({ entry_name => timestamp })
+        listing.merge!({ entry_name => etag })
       end
 
       listing
     end
 
     def directory_entries(user, directory)
-      directory = "/" if directory == ""
-
-      user_keys = data_bucket.get_index("user_id_bin", user)
-      directory_keys = data_bucket.get_index("directory_bin", directory)
-
-      all_keys = user_keys & directory_keys
+      all_keys = user_directory_keys(user, directory, data_bucket)
       return [] if all_keys.empty?
 
       map_query = <<-EOH
@@ -256,48 +272,53 @@ module RemoteStorage
           key_name = keys.join(':');
           last_modified_date = v.values[0]['metadata']['X-Riak-Last-Modified'];
           timestamp = v.values[0]['metadata']['X-Riak-Meta']['X-Riak-Meta-Timestamp'];
+          etag = v.values[0]['metadata']['X-Riak-VTag'];
           return [{
             name: key_name,
             last_modified: last_modified_date,
             timestamp: timestamp,
+            etag: etag
           }];
         }
       EOH
 
-      map_reduce = ::Riak::MapReduce.new(client)
-      all_keys.each do |key|
-        map_reduce.add(data_bucket.name, key)
-      end
-
-      map_reduce.
-        map(map_query, :keep => true).
-        run
+      run_map_reduce(data_bucket, all_keys, map_query)
     end
 
     def sub_directories(user, directory)
-      directory = "/" if directory == ""
-
-      user_keys = directory_bucket.get_index("user_id_bin", user)
-      directory_keys = directory_bucket.get_index("directory_bin", directory)
-
-      all_keys = user_keys & directory_keys
+      all_keys = user_directory_keys(user, directory, directory_bucket)
       return [] if all_keys.empty?
 
       map_query = <<-EOH
         function(v){
           keys = v.key.split(':');
           key_name = keys[keys.length-1];
-          timestamp = v.values[0]['data']
+          timestamp = v.values[0]['data'];
+          etag = v.values[0]['metadata']['X-Riak-VTag'];
           return [{
             name: key_name,
             timestamp: timestamp,
+            etag: etag
           }];
         }
       EOH
 
+      run_map_reduce(directory_bucket, all_keys, map_query)
+    end
+
+    def user_directory_keys(user, directory, bucket)
+      directory = "/" if directory == ""
+
+      user_keys = bucket.get_index("user_id_bin", user)
+      directory_keys = bucket.get_index("directory_bin", directory)
+
+      user_keys & directory_keys
+    end
+
+    def run_map_reduce(bucket, keys, map_query)
       map_reduce = ::Riak::MapReduce.new(client)
-      all_keys.each do |key|
-        map_reduce.add(directory_bucket.name, key)
+      keys.each do |key|
+        map_reduce.add(bucket.name, key)
       end
 
       map_reduce.
diff --git a/liquor-cabinet.rb b/liquor-cabinet.rb
index 1df2e25..71eecd1 100644
--- a/liquor-cabinet.rb
+++ b/liquor-cabinet.rb
@@ -42,7 +42,8 @@ class LiquorCabinet < Sinatra::Base
     before path do
       headers 'Access-Control-Allow-Origin' => '*',
               'Access-Control-Allow-Methods' => 'GET, PUT, DELETE',
-              'Access-Control-Allow-Headers' => 'Authorization, Content-Type, Origin'
+              'Access-Control-Allow-Headers' => 'Authorization, Content-Type, Origin, If-Match, If-None-Match',
+              'Access-Control-Expose-Headers' => 'ETag'
       headers['Access-Control-Allow-Origin'] = env["HTTP_ORIGIN"] if env["HTTP_ORIGIN"]
       headers['Cache-Control'] = 'no-cache'
 
diff --git a/spec/directories_spec.rb b/spec/directories_spec.rb
index 3292017..1e5f656 100644
--- a/spec/directories_spec.rb
+++ b/spec/directories_spec.rb
@@ -19,17 +19,18 @@ describe "Directories" do
       put "/jimmy/tasks/http%3A%2F%2F5apps.com", "prettify design"
     end
 
-    it "lists the objects with a timestamp of the last modification" do
+    it "lists the objects with their version" do
       get "/jimmy/tasks/"
 
       last_response.status.must_equal 200
       last_response.content_type.must_equal "application/json"
 
+      foo = data_bucket.get("jimmy:tasks:foo")
+
       content = JSON.parse(last_response.body)
       content.must_include "http://5apps.com"
       content.must_include "foo"
-      content["foo"].must_be_kind_of Integer
-      content["foo"].to_s.length.must_equal 13
+      content["foo"].must_equal foo.etag.gsub(/"/, "")
     end
 
     it "has a Last-Modifier header set" do
@@ -44,17 +45,57 @@ describe "Directories" do
       last_modified.day.must_equal now.day
     end
 
+    it "has an ETag header set" do
+      get "/jimmy/tasks/"
+
+      last_response.status.must_equal 200
+      last_response.headers["ETag"].wont_be_nil
+
+      # check that ETag stays the same
+      etag = last_response.headers["ETag"]
+      get "/jimmy/tasks/"
+      last_response.headers["ETag"].must_equal etag
+    end
+
     it "has CORS headers set" do
       get "/jimmy/tasks/"
 
       last_response.status.must_equal 200
       last_response.headers["Access-Control-Allow-Origin"].must_equal "*"
       last_response.headers["Access-Control-Allow-Methods"].must_equal "GET, PUT, DELETE"
-      last_response.headers["Access-Control-Allow-Headers"].must_equal "Authorization, Content-Type, Origin"
+      last_response.headers["Access-Control-Allow-Headers"].must_equal "Authorization, Content-Type, Origin, If-Match, If-None-Match"
+      last_response.headers["Access-Control-Expose-Headers"].must_equal "ETag"
+    end
+
+    context "when If-None-Match header is set" do
+      before do
+        get "/jimmy/tasks/"
+
+        @etag = last_response.headers["ETag"]
+      end
+
+      it "responds with 'not modified' when it matches the current ETag" do
+        header "If-None-Match", @etag
+        get "/jimmy/tasks/"
+
+        last_response.status.must_equal 304
+        last_response.body.must_be_empty
+      end
+
+      it "responds normally when it does not match the current ETag" do
+        header "If-None-Match", "FOO"
+        get "/jimmy/tasks/"
+
+        last_response.status.must_equal 200
+        last_response.body.wont_be_empty
+      end
     end
 
     context "with sub-directories" do
       before do
+        get "/jimmy/tasks/"
+        @old_etag = last_response.headers["ETag"]
+
         put "/jimmy/tasks/home/laundry", "do the laundry"
       end
 
@@ -63,12 +104,20 @@ describe "Directories" do
 
         last_response.status.must_equal 200
 
+        home = directory_bucket.get("jimmy:tasks/home")
+
         content = JSON.parse(last_response.body)
         content.must_include "foo"
         content.must_include "http://5apps.com"
         content.must_include "home/"
-        content["home/"].must_be_kind_of Integer
-        content["home/"].to_s.length.must_equal 13
+        content["home/"].must_equal home.etag.gsub(/"/, "")
+      end
+
+      it "updates the ETag of the parent directory" do
+        get "/jimmy/tasks/"
+
+        last_response.headers["ETag"].wont_be_nil
+        last_response.headers["ETag"].wont_equal @old_etag
       end
 
       context "for a different user" do
@@ -102,10 +151,11 @@ describe "Directories" do
 
           last_response.status.must_equal 200
 
+          projects = directory_bucket.get("jimmy:tasks/private/projects")
+
           content = JSON.parse(last_response.body)
           content.must_include "projects/"
-          content["projects/"].must_be_kind_of Integer
-          content["projects/"].to_s.length.must_equal 13
+          content["projects/"].must_equal projects.etag.gsub(/"/, "")
         end
 
         it "updates the timestamps of the existing directory objects" do
@@ -137,10 +187,11 @@ describe "Directories" do
 
             last_response.status.must_equal 200
 
+            jaypeg = data_bucket.get("jimmy:tasks:jaypeg.jpg")
+
             content = JSON.parse(last_response.body)
             content.must_include "jaypeg.jpg"
-            content["jaypeg.jpg"].must_be_kind_of Integer
-            content["jaypeg.jpg"].to_s.length.must_equal 13
+            content["jaypeg.jpg"].must_equal jaypeg.etag.gsub(/"/, "")
           end
         end
 
@@ -157,10 +208,11 @@ describe "Directories" do
 
             last_response.status.must_equal 200
 
+            jaypeg = data_bucket.get("jimmy:tasks:jaypeg.jpg")
+
             content = JSON.parse(last_response.body)
             content.must_include "jaypeg.jpg"
-            content["jaypeg.jpg"].must_be_kind_of Integer
-            content["jaypeg.jpg"].to_s.length.must_equal 13
+            content["jaypeg.jpg"].must_equal jaypeg.etag.gsub(/"/, "")
           end
         end
       end
@@ -176,10 +228,11 @@ describe "Directories" do
 
         last_response.status.must_equal 200
 
+        laundry = data_bucket.get("jimmy:tasks/home:laundry")
+
         content = JSON.parse(last_response.body)
         content.must_include "laundry"
-        content["laundry"].must_be_kind_of Integer
-        content["laundry"].to_s.length.must_equal 13
+        content["laundry"].must_equal laundry.etag.gsub(/"/, "")
       end
     end
 
@@ -187,8 +240,7 @@ describe "Directories" do
       it "returns an empty listing" do
         get "/jimmy/documents/notfound/"
 
-        last_response.status.must_equal 200
-        last_response.body.must_equal "{}"
+        last_response.status.must_equal 404
       end
     end
 
@@ -254,12 +306,20 @@ describe "Directories" do
 
         last_response.status.must_equal 200
 
+        tasks = directory_bucket.get("jimmy:tasks")
+
         content = JSON.parse(last_response.body)
         content.must_include "root-1"
         content.must_include "root-2"
         content.must_include "tasks/"
-        content["tasks/"].must_be_kind_of Integer
-        content["tasks/"].to_s.length.must_equal 13
+        content["tasks/"].must_equal tasks.etag.gsub(/"/, "")
+      end
+
+      it "has an ETag header set" do
+        get "/jimmy/"
+
+        last_response.status.must_equal 200
+        last_response.headers["ETag"].wont_be_nil
       end
     end
 
@@ -281,6 +341,13 @@ describe "Directories" do
           content = JSON.parse(last_response.body)
           content.must_include "5apps"
         end
+
+        it "has an ETag header set" do
+          get "/jimmy/public/bookmarks/"
+
+          last_response.status.must_equal 200
+          last_response.headers["ETag"].wont_be_nil
+        end
       end
 
       context "when directly authorized for the public directory" do
@@ -323,9 +390,11 @@ describe "Directories" do
   describe "directory object" do
     describe "PUT file" do
       context "no existing directory object" do
-        it "creates a new directory object" do
+        before do
           put "/jimmy/tasks/home/trash", "take out the trash"
+        end
 
+        it "creates a new directory object" do
           object = data_bucket.get("jimmy:tasks/home:trash")
           directory = directory_bucket.get("jimmy:tasks/home")
 
@@ -334,15 +403,11 @@ describe "Directories" do
         end
 
         it "sets the correct index for the directory object" do
-          put "/jimmy/tasks/home/trash", "take out the trash"
-
           object = directory_bucket.get("jimmy:tasks/home")
           object.indexes["directory_bin"].must_include "tasks"
         end
 
         it "creates directory objects for the parent directories" do
-          put "/jimmy/tasks/home/trash", "take out the trash"
-
           object = directory_bucket.get("jimmy:tasks")
           object.indexes["directory_bin"].must_include "/"
           object.data.wont_be_nil
@@ -355,10 +420,7 @@ describe "Directories" do
 
       context "existing directory object" do
         before do
-          directory = directory_bucket.new("jimmy:tasks/home")
-          directory.content_type = "text/plain"
-          directory.data = (2.seconds.ago.to_f * 1000).to_i
-          directory.store
+          put "/jimmy/tasks/home/trash", "collect some trash"
         end
 
         it "updates the timestamp of the directory" do
@@ -383,7 +445,8 @@ describe "Directories" do
 
       last_response.headers["Access-Control-Allow-Origin"].must_equal "*"
       last_response.headers["Access-Control-Allow-Methods"].must_equal "GET, PUT, DELETE"
-      last_response.headers["Access-Control-Allow-Headers"].must_equal "Authorization, Content-Type, Origin"
+      last_response.headers["Access-Control-Allow-Headers"].must_equal "Authorization, Content-Type, Origin, If-Match, If-None-Match"
+      last_response.headers["Access-Control-Expose-Headers"].must_equal "ETag"
     end
 
     context "sub-directories" do
@@ -394,7 +457,8 @@ describe "Directories" do
 
         last_response.headers["Access-Control-Allow-Origin"].must_equal "*"
         last_response.headers["Access-Control-Allow-Methods"].must_equal "GET, PUT, DELETE"
-        last_response.headers["Access-Control-Allow-Headers"].must_equal "Authorization, Content-Type, Origin"
+        last_response.headers["Access-Control-Allow-Headers"].must_equal "Authorization, Content-Type, Origin, If-Match, If-None-Match"
+        last_response.headers["Access-Control-Expose-Headers"].must_equal "ETag"
       end
     end
 
@@ -406,7 +470,8 @@ describe "Directories" do
 
         last_response.headers["Access-Control-Allow-Origin"].must_equal "*"
         last_response.headers["Access-Control-Allow-Methods"].must_equal "GET, PUT, DELETE"
-        last_response.headers["Access-Control-Allow-Headers"].must_equal "Authorization, Content-Type, Origin"
+        last_response.headers["Access-Control-Allow-Headers"].must_equal "Authorization, Content-Type, Origin, If-Match, If-None-Match"
+        last_response.headers["Access-Control-Expose-Headers"].must_equal "ETag"
       end
     end
   end
@@ -450,6 +515,31 @@ describe "Directories" do
         directory_bucket.get("jimmy:").wont_be_nil
       end
 
+      it "updates the ETag headers of all parent directories" do
+        get "/jimmy/tasks/home/"
+        home_etag = last_response.headers["ETag"]
+
+        get "/jimmy/tasks/"
+        tasks_etag = last_response.headers["ETag"]
+
+        get "/jimmy/"
+        root_etag = last_response.headers["ETag"]
+
+        delete "/jimmy/tasks/home/trash"
+
+        get "/jimmy/tasks/home/"
+        last_response.headers["ETag"].wont_be_nil
+        last_response.headers["ETag"].wont_equal home_etag
+
+        get "/jimmy/tasks/"
+        last_response.headers["ETag"].wont_be_nil
+        last_response.headers["ETag"].wont_equal tasks_etag
+
+        get "/jimmy/"
+        last_response.headers["ETag"].wont_be_nil
+        last_response.headers["ETag"].wont_equal root_etag
+      end
+
       describe "timestamps" do
         before do
           @old_timestamp = (2.seconds.ago.to_f * 1000).to_i
diff --git a/spec/permissions_spec.rb b/spec/permissions_spec.rb
index d4f7bbf..8f13a16 100644
--- a/spec/permissions_spec.rb
+++ b/spec/permissions_spec.rb
@@ -345,7 +345,7 @@ describe "Permissions" do
         it "allows GET requests" do
           get "/jimmy/public/tasks/"
 
-          last_response.status.must_equal 200
+          last_response.status.must_equal 404
         end
 
         it "allows PUT requests" do
@@ -403,19 +403,19 @@ describe "Permissions" do
         end
 
         it "allows GET requests" do
-          get "/jimmy/tasks/"
+          get "/jimmy/public/tasks/"
 
-          last_response.status.must_equal 200
+          last_response.status.must_equal 404
         end
 
         it "disallows PUT requests" do
-          put "/jimmy/tasks/foo", "some text"
+          put "/jimmy/public/tasks/foo", "some text"
 
           last_response.status.must_equal 403
         end
 
         it "disallows DELETE requests" do
-          delete "/jimmy/tasks/hello"
+          delete "/jimmy/public/tasks/hello"
 
           last_response.status.must_equal 403
         end
diff --git a/spec/riak_spec.rb b/spec/riak_spec.rb
index c34a601..65bbfae 100644
--- a/spec/riak_spec.rb
+++ b/spec/riak_spec.rb
@@ -32,6 +32,11 @@ describe "App with Riak backend" do
       last_modified.year.must_equal now.year
       last_modified.day.must_equal now.day
     end
+
+    it "has an ETag header set" do
+      last_response.status.must_equal 200
+      last_response.headers["ETag"].wont_be_nil
+    end
   end
 
   describe "GET data with custom content type" do
@@ -58,19 +63,42 @@ describe "App with Riak backend" do
       object.data = "some private text data"
       object.store
 
+      @etag = object.etag
+
       auth = auth_bucket.new("jimmy:123")
       auth.data = ["documents", "public"]
       auth.store
     end
 
     describe "GET" do
-      it "returns the value" do
+      before do
         header "Authorization", "Bearer 123"
+      end
+
+      it "returns the value" do
         get "/jimmy/documents/foo"
 
         last_response.status.must_equal 200
         last_response.body.must_equal "some private text data"
       end
+
+      describe "when If-None-Match header is set" do
+        it "responds with 'not modified' when it matches the current ETag" do
+          header "If-None-Match", @etag
+          get "/jimmy/documents/foo"
+
+          last_response.status.must_equal 304
+          last_response.body.must_be_empty
+        end
+
+        it "responds normally when it does not match the current ETag" do
+          header "If-None-Match", "FOO"
+          get "/jimmy/documents/foo"
+
+          last_response.status.must_equal 200
+          last_response.body.must_equal "some private text data"
+        end
+      end
     end
 
     describe "GET nonexisting key" do
@@ -102,6 +130,10 @@ describe "App with Riak backend" do
           data_bucket.get("jimmy:documents:bar").content_type.must_equal "text/plain; charset=utf-8"
         end
 
+        it "sets the ETag header" do
+          last_response.headers["ETag"].wont_be_nil
+        end
+
         it "indexes the data set" do
           indexes = data_bucket.get("jimmy:documents:bar").indexes
           indexes["user_id_bin"].must_be_kind_of Set
@@ -197,15 +229,18 @@ describe "App with Riak backend" do
       describe "with existing content" do
         before do
           put "/jimmy/documents/archive/foo", "lorem ipsum"
-          put "/jimmy/documents/archive/foo", "some awesome content"
         end
 
         it "saves the value" do
+          put "/jimmy/documents/archive/foo", "some awesome content"
+
           last_response.status.must_equal 200
           data_bucket.get("jimmy:documents/archive:foo").data.must_equal "some awesome content"
         end
 
         it "logs the operations" do
+          put "/jimmy/documents/archive/foo", "some awesome content"
+
           objects = []
           opslog_bucket.keys.each { |k| objects << opslog_bucket.get(k) rescue nil }
 
@@ -220,22 +255,74 @@ describe "App with Riak backend" do
           update_entry.indexes["user_id_bin"].must_include "jimmy"
         end
 
-        describe "when no serializer is registered for the given content-type" do
-          before do
-            header "Content-Type", "text/html; charset=UTF-8"
-            put "/jimmy/documents/html", '<html></html>'
-            put "/jimmy/documents/html", '<html><body></body></html>'
-          end
+        it "changes the ETag header" do
+          old_etag = last_response.headers["ETag"]
+          put "/jimmy/documents/archive/foo", "some awesome content"
 
-          it "saves the value" do
+          last_response.headers["ETag"].wont_be_nil
+          last_response.headers["ETag"].wont_equal old_etag
+        end
+
+        describe "when If-Match header is set" do
+          it "allows the request if the header matches the current ETag" do
+            old_etag = last_response.headers["ETag"]
+            header "If-Match", old_etag
+
+            put "/jimmy/documents/archive/foo", "some awesome content"
             last_response.status.must_equal 200
-            data_bucket.get("jimmy:documents:html").raw_data.must_equal "<html><body></body></html>"
+
+            get "/jimmy/documents/archive/foo"
+            last_response.body.must_equal "some awesome content"
           end
 
-          it "uses the requested content type" do
-            data_bucket.get("jimmy:documents:html").content_type.must_equal "text/html; charset=UTF-8"
+          it "fails the request if the header does not match the current ETag" do
+            header "If-Match", "WONTMATCH"
+
+            put "/jimmy/documents/archive/foo", "some awesome content"
+            last_response.status.must_equal 412
+
+            get "/jimmy/documents/archive/foo"
+            last_response.body.must_equal "lorem ipsum"
           end
         end
+
+        describe "when If-None-Match header is set" do
+          before do
+            header "If-None-Match", "*"
+          end
+
+          it "fails when the document already exists" do
+            put "/jimmy/documents/archive/foo", "some awesome content"
+
+            last_response.status.must_equal 412
+
+            get "/jimmy/documents/archive/foo"
+            last_response.body.must_equal "lorem ipsum"
+          end
+
+          it "succeeds when the document does not exist" do
+            put "/jimmy/documents/archive/bar", "my little content"
+
+            last_response.status.must_equal 200
+          end
+        end
+      end
+
+      describe "exsting content without serializer registered for the given content-type" do
+        before do
+          header "Content-Type", "text/html; charset=UTF-8"
+          put "/jimmy/documents/html", '<html></html>'
+          put "/jimmy/documents/html", '<html><body></body></html>'
+        end
+
+        it "saves the value" do
+          last_response.status.must_equal 200
+          data_bucket.get("jimmy:documents:html").raw_data.must_equal "<html><body></body></html>"
+        end
+
+        it "uses the requested content type" do
+          data_bucket.get("jimmy:documents:html").content_type.must_equal "text/html; charset=UTF-8"
+        end
       end
 
       describe "public data" do
@@ -282,13 +369,23 @@ describe "App with Riak backend" do
             last_response.body.must_equal @image
           end
 
-          # it "indexes the binary set" do
-          #   indexes = binary_bucket.get("jimmy:documents:jaypeg").indexes
-          #   indexes["user_id_bin"].must_be_kind_of Set
-          #   indexes["user_id_bin"].must_include "jimmy"
+          it "responds with an ETag header" do
+            last_response.headers["ETag"].wont_be_nil
+            etag = last_response.headers["ETag"]
 
-          #   indexes["directory_bin"].must_include "documents"
-          # end
+            get "/jimmy/documents/jaypeg"
+
+            last_response.headers["ETag"].wont_be_nil
+            last_response.headers["ETag"].must_equal etag
+          end
+
+          it "changes the ETag when updating the file" do
+            old_etag = last_response.headers["ETag"]
+            put "/jimmy/documents/jaypeg", @image
+
+            last_response.headers["ETag"].wont_be_nil
+            last_response.headers["ETag"].wont_equal old_etag
+          end
 
           it "logs the operation" do
             objects = []
@@ -322,14 +419,6 @@ describe "App with Riak backend" do
             last_response.status.must_equal 200
             last_response.body.must_equal @image
           end
-
-          # it "indexes the binary set" do
-          #   indexes = binary_bucket.get("jimmy:documents:jaypeg").indexes
-          #   indexes["user_id_bin"].must_be_kind_of Set
-          #   indexes["user_id_bin"].must_include "jimmy"
-
-          #   indexes["directory_bin"].must_include "documents"
-          # end
         end
       end
 
@@ -376,24 +465,33 @@ describe "App with Riak backend" do
     describe "DELETE" do
       before do
         header "Authorization", "Bearer 123"
-        delete "/jimmy/documents/foo"
       end
 
-      it "removes the key" do
-        last_response.status.must_equal 204
-        lambda {
-          data_bucket.get("jimmy:documents:foo")
-        }.must_raise Riak::HTTPFailedRequest
-      end
+      describe "basics" do
+        before do
+          delete "/jimmy/documents/foo"
+        end
 
-      it "logs the operation" do
-        objects = []
-        opslog_bucket.keys.each { |k| objects << opslog_bucket.get(k) rescue nil }
+        it "removes the key" do
+          last_response.status.must_equal 204
+          lambda {
+            data_bucket.get("jimmy:documents:foo")
+          }.must_raise Riak::HTTPFailedRequest
+        end
 
-        log_entry = objects.select{|o| o.data["count"] == -1}.first
-        log_entry.data["size"].must_equal(-22)
-        log_entry.data["category"].must_equal "documents"
-        log_entry.indexes["user_id_bin"].must_include "jimmy"
+        it "logs the operation" do
+          objects = []
+          opslog_bucket.keys.each { |k| objects << opslog_bucket.get(k) rescue nil }
+
+          log_entry = objects.select{|o| o.data["count"] == -1}.first
+          log_entry.data["size"].must_equal(-22)
+          log_entry.data["category"].must_equal "documents"
+          log_entry.indexes["user_id_bin"].must_include "jimmy"
+        end
+
+        it "sets the ETag header" do
+          last_response.headers["ETag"].wont_be_nil
+        end
       end
 
       context "non-existing object" do
@@ -401,10 +499,39 @@ describe "App with Riak backend" do
           delete "/jimmy/documents/foozius"
         end
 
+        it "responds with 404" do
+          last_response.status.must_equal 404
+        end
+
         it "doesn't log the operation" do
           objects = []
           opslog_bucket.keys.each { |k| objects << opslog_bucket.get(k) rescue nil }
-          objects.select{|o| o.data["count"] == -1}.size.must_equal 1
+          objects.select{|o| o.data["count"] == -1}.size.must_equal 0
+        end
+      end
+
+      context "when an If-Match header is given" do
+        it "allows the request if it matches the current ETag" do
+          get "/jimmy/documents/foo"
+          old_etag = last_response.headers["ETag"]
+          header "If-Match", old_etag
+
+          delete "/jimmy/documents/foo"
+          last_response.status.must_equal 204
+
+          get "/jimmy/documents/foo"
+          last_response.status.must_equal 404
+        end
+
+        it "fails the request if it does not match the current ETag" do
+          header "If-Match", "WONTMATCH"
+
+          delete "/jimmy/documents/foo"
+          last_response.status.must_equal 412
+
+          get "/jimmy/documents/foo"
+          last_response.status.must_equal 200
+          last_response.body.must_equal "some private text data"
         end
       end