diff --git a/lib/rdf.ex b/lib/rdf.ex
index c98df3e..1c0013a 100644
--- a/lib/rdf.ex
+++ b/lib/rdf.ex
@@ -1,8 +1,6 @@
 defmodule RDF do
   alias RDF.{Vocabulary, Literal, BlankNode, Triple}
 
-  defmodule InvalidURIError, do: defexception [:message]
-
   @doc """
   Generator function for URIs from strings or term atoms of a `RDF.Vocabulary`.
 
@@ -27,7 +25,7 @@ defmodule RDF do
     if uri?(parsed_uri) do
       parsed_uri
     else
-      raise InvalidURIError, ~s(string "#{string}" is not a valid URI)
+      raise RDF.InvalidURIError, ~s(string "#{string}" is not a valid URI)
     end
   end
 
diff --git a/lib/rdf/exceptions.ex b/lib/rdf/exceptions.ex
new file mode 100644
index 0000000..47214d9
--- /dev/null
+++ b/lib/rdf/exceptions.ex
@@ -0,0 +1,48 @@
+defmodule RDF.InvalidURIError do
+  defexception [:message]
+end
+
+defmodule RDF.InvalidLiteralError do
+  defexception [:message]
+end
+
+defmodule RDF.Triple.InvalidSubjectError do
+  defexception [:subject]
+
+  def message(%{subject: subject}) do
+    "'#{inspect(subject)}' is not a valid subject of a RDF.Triple"
+  end
+end
+
+defmodule RDF.Triple.InvalidPredicateError do
+  defexception [:predicate]
+
+  def message(%{predicate: predicate}) do
+    "'#{inspect(predicate)}' is not a valid predicate of a RDF.Triple"
+  end
+end
+
+
+defmodule RDF.Vocabulary.InvalidBaseURIError do
+  defexception [:message]
+end
+
+defmodule RDF.Vocabulary.UndefinedTermError do
+  defexception [:message]
+end
+
+defmodule RDF.Vocabulary.InvalidTermError do
+  defexception [:message]
+end
+
+
+defmodule RDF.InvalidRepoURLError do
+  defexception [:message, :url]
+
+  def exception(opts) do
+    url = Keyword.fetch!(opts, :url)
+    msg = Keyword.fetch!(opts, :message)
+    msg = "invalid url #{url}, #{msg}"
+    %__MODULE__{message: msg, url: url}
+  end
+end
diff --git a/lib/rdf/literal.ex b/lib/rdf/literal.ex
index 616a5fe..4ac3f5f 100644
--- a/lib/rdf/literal.ex
+++ b/lib/rdf/literal.ex
@@ -8,8 +8,6 @@ defmodule RDF.Literal do
 
   alias RDF.{XSD, RDFS}
 
-  defmodule InvalidLiteralError, do: defexception [:message]
-
   @doc """
   Creates a new `RDF.Literal` of the given value and tries to infer an appropriate XSD datatype.
 
@@ -57,7 +55,7 @@ defmodule RDF.Literal do
 #  def new(value) when is_reference(value), do:
 
   def new(value) do
-    raise InvalidLiteralError, "#{inspect value} not convertible to a RDF.Literal"
+    raise RDF.InvalidLiteralError, "#{inspect value} not convertible to a RDF.Literal"
   end
 
   def new(value, language: language) when is_binary(value) do
diff --git a/lib/rdf/triple.ex b/lib/rdf/triple.ex
index ce274aa..acfb296 100644
--- a/lib/rdf/triple.ex
+++ b/lib/rdf/triple.ex
@@ -16,18 +16,6 @@ defmodule RDF.Triple do
   @type convertible_predicate :: predicate | atom | String.t
   @type convertible_object :: object | atom | String.t # TODO: all basic Elixir types convertible to Literals
 
-  defmodule InvalidSubjectError do
-    defexception [:subject]
-    def message(%{subject: subject}),
-      do: "'#{inspect(subject)}' is not a valid subject of a RDF.Triple"
-  end
-
-  defmodule InvalidPredicateError do
-    defexception [:predicate]
-    def message(%{predicate: predicate}),
-      do: "'#{inspect(predicate)}' is not a valid predicate of a RDF.Triple"
-  end
-
   @doc """
   Creates a `RDF.Triple` with proper RDF values.
 
@@ -68,13 +56,13 @@ defmodule RDF.Triple do
   def convert_subject(uri = %URI{}), do: uri
   def convert_subject(bnode = %BlankNode{}), do: bnode
   def convert_subject(uri) when is_atom(uri) or is_binary(uri), do: RDF.uri(uri)
-  def convert_subject(arg), do: raise InvalidSubjectError, subject: arg
+  def convert_subject(arg), do: raise RDF.Triple.InvalidSubjectError, subject: arg
 
   @doc false
   def convert_predicate(uri)
   def convert_predicate(uri = %URI{}), do: uri
   def convert_predicate(uri) when is_atom(uri) or is_binary(uri), do: RDF.uri(uri)
-  def convert_predicate(arg), do: raise InvalidPredicateError, predicate: arg
+  def convert_predicate(arg), do: raise RDF.Triple.InvalidPredicateError, predicate: arg
 
   @doc false
   def convert_object(uri)
diff --git a/lib/rdf/vocabulary.ex b/lib/rdf/vocabulary.ex
index 9d8ee08..9942f13 100644
--- a/lib/rdf/vocabulary.ex
+++ b/lib/rdf/vocabulary.ex
@@ -67,10 +67,6 @@ defmodule RDF.Vocabulary do # or RDF.URI.Namespace?
   `__base_uri__` and `__terms__` ...
   """
 
-  defmodule InvalidBaseURIError, do: defexception [:message]
-  defmodule UndefinedTermError, do: defexception [:message]
-  defmodule InvalidTermError, do: defexception [:message]
-
   defmacro __using__(opts) do
     quote bind_quoted: [opts: opts], unquote: true do
       import unquote(__MODULE__)
@@ -87,9 +83,9 @@ defmodule RDF.Vocabulary do # or RDF.URI.Namespace?
         @base_uri base_uri
       else
         :error ->
-          raise InvalidBaseURIError, "required base_uri missing"
+          raise RDF.Vocabulary.InvalidBaseURIError, "required base_uri missing"
         false  ->
-          raise InvalidBaseURIError,
+          raise RDF.Vocabulary.InvalidBaseURIError,
                   "a base_uri without a trailing '/' or '#' is invalid"
       end
 
@@ -113,7 +109,7 @@ defmodule RDF.Vocabulary do # or RDF.URI.Namespace?
           if Enum.member?(@terms, term) do
             RDF.Vocabulary.term_to_uri(@base_uri, term)
           else
-            raise UndefinedTermError,
+            raise RDF.Vocabulary.UndefinedTermError,
               "undefined term #{term} in strict vocabulary #{__MODULE__}"
           end
         end
@@ -158,7 +154,7 @@ defmodule RDF.Vocabulary do # or RDF.URI.Namespace?
     |> Enum.map(&String.reverse/1)
     |> Enum.map(&String.to_existing_atom/1) do
       [term, vocabulary] -> vocabulary.uri(term)
-      _ -> raise InvalidTermError, ""
+      _ -> raise RDF.Vocabulary.InvalidTermError, ""
     end
 
   end
diff --git a/test/unit/description_test.exs b/test/unit/description_test.exs
index 5700dab..c3c19ec 100644
--- a/test/unit/description_test.exs
+++ b/test/unit/description_test.exs
@@ -143,7 +143,7 @@ defmodule RDF.DescriptionTest do
         Description.add(description, {"not a URI", uri(EX.Object)})
       end
 
-      assert_raise RDF.Literal.InvalidLiteralError, fn ->
+      assert_raise RDF.InvalidLiteralError, fn ->
         Description.add(description, {EX.prop, self})
       end
     end
diff --git a/test/unit/graph_test.exs b/test/unit/graph_test.exs
index 2693d8c..1acb192 100644
--- a/test/unit/graph_test.exs
+++ b/test/unit/graph_test.exs
@@ -103,7 +103,7 @@ defmodule RDF.GraphTest do
       assert_raise RDF.InvalidURIError, fn ->
         Graph.add(graph, {"not a URI", EX.predicate, uri(EX.Object)})
       end
-      assert_raise RDF.Literal.InvalidLiteralError, fn ->
+      assert_raise RDF.InvalidLiteralError, fn ->
         Graph.add(graph, {EX.Subject, EX.prop, self})
       end
     end