diff --git a/app/models/concerns/metadata/always_public_concern.rb b/app/models/concerns/metadata/always_public_concern.rb
new file mode 100644
index 00000000..40cc4b45
--- /dev/null
+++ b/app/models/concerns/metadata/always_public_concern.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+module Metadata
+  # Mixin para campos que no se pueden cifrar
+  module AlwaysPublicConcern
+    extend ActiveSupport::Concern
+
+    included do
+      # Siempre son públicos
+      #
+      # @return [Boolean]
+      def private?
+        false
+      end
+
+      private
+
+      def decrypt(value)
+        raise NotImplementedError, 'Este atributo no se cifra'
+      end
+
+      alias_method :encrypt, :decrypt
+    end
+  end
+end
diff --git a/app/models/concerns/metadata/content_concern.rb b/app/models/concerns/metadata/content_concern.rb
new file mode 100644
index 00000000..2efb6bf3
--- /dev/null
+++ b/app/models/concerns/metadata/content_concern.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+module Metadata
+  # Mixin para campos que son el contenido de un documento
+  module ContentConcern
+    extend ActiveSupport::Concern
+
+    included do
+      # Son parte del contenido
+      #
+      # @return [Boolean]
+      def front_matter?
+        false
+      end
+    end
+  end
+end
diff --git a/app/models/concerns/metadata/front_matter_concern.rb b/app/models/concerns/metadata/front_matter_concern.rb
new file mode 100644
index 00000000..883211a7
--- /dev/null
+++ b/app/models/concerns/metadata/front_matter_concern.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+module Metadata
+  # Mixin para campos que son el encabezado de un documento
+  module FrontMatterConcern
+    extend ActiveSupport::Concern
+
+    included do
+      # Son parte del encabezado
+      #
+      # @return [Boolean]
+      def front_matter?
+        true
+      end
+    end
+  end
+end
diff --git a/app/models/concerns/metadata/indexable_concern.rb b/app/models/concerns/metadata/indexable_concern.rb
new file mode 100644
index 00000000..d801642f
--- /dev/null
+++ b/app/models/concerns/metadata/indexable_concern.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module Metadata
+  # Mixin para generar atributos indexables
+  module IndexableConcern
+    extend ActiveSupport::Concern
+
+    included do
+      # Siempre indexar, a menos que sea un campo privado
+      #
+      # @return [Boolean]
+      def indexable?
+        true && !private?
+      end
+
+      # Por defecto los valores indexables son el valor actual
+      alias_method :indexable_values, :value
+    end
+  end
+end
diff --git a/app/models/concerns/metadata/non_indexable_concern.rb b/app/models/concerns/metadata/non_indexable_concern.rb
new file mode 100644
index 00000000..6cf807a7
--- /dev/null
+++ b/app/models/concerns/metadata/non_indexable_concern.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module Metadata
+  # Mixin para nunca generar atributos indexables
+  module NonIndexableConcern
+    extend ActiveSupport::Concern
+
+    included do
+      # Nunca
+      def indexable?
+        false
+      end
+
+      # Lanzar un error para poder enterarnos de la inconsistencia
+      def indexable_values
+        raise NotImplementedError, 'Este atributo no es indexable'
+      end
+    end
+  end
+end