diff --git a/lib/samly.ex b/lib/samly.ex
index e390abf..601e6e8 100644
--- a/lib/samly.ex
+++ b/lib/samly.ex
@@ -59,4 +59,9 @@ defmodule Samly do
   def get_attribute(%Assertion{} = assertion, name) do
     Map.get(assertion.computed, name) || Map.get(assertion.attributes, name)
   end
+
+  def logout(conn) do
+    conn
+    |> Conn.delete_session("samly_assertion_key")
+  end
 end
diff --git a/lib/samly/idp_data.ex b/lib/samly/idp_data.ex
index 0aa662c..96d382f 100644
--- a/lib/samly/idp_data.ex
+++ b/lib/samly/idp_data.ex
@@ -62,26 +62,30 @@ defmodule Samly.IdpData do
           valid?: boolean()
         }
 
-  @entdesc "md:EntityDescriptor"
-  @idpdesc "md:IDPSSODescriptor"
+  @entsdesc "EntitiesDescriptor"
+  @entdesc "EntityDescriptor"
+  @idpdesc "IDPSSODescriptor"
   @signedreq "WantAuthnRequestsSigned"
-  @nameid "md:NameIDFormat"
-  @keydesc "md:KeyDescriptor"
-  @ssos "md:SingleSignOnService"
-  @slos "md:SingleLogoutService"
+  @nameid "NameIDFormat"
+  @keydesc "KeyDescriptor"
+  @ssos "SingleSignOnService"
+  @slos "SingleLogoutService"
   @redirect "urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect"
   @post "urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST"
 
   @entity_id_selector ~x"//#{@entdesc}/@entityID"sl
-  @nameid_format_selector ~x"//#{@entdesc}/#{@idpdesc}/#{@nameid}/text()"s
   @req_signed_selector ~x"//#{@entdesc}/#{@idpdesc}/@#{@signedreq}"s
-  @sso_redirect_url_selector ~x"//#{@entdesc}/#{@idpdesc}/#{@ssos}[@Binding = '#{@redirect}']/@Location"s
-  @sso_post_url_selector ~x"//#{@entdesc}/#{@idpdesc}/#{@ssos}[@Binding = '#{@post}']/@Location"s
-  @slo_redirect_url_selector ~x"//#{@entdesc}/#{@idpdesc}/#{@slos}[@Binding = '#{@redirect}']/@Location"s
-  @slo_post_url_selector ~x"//#{@entdesc}/#{@idpdesc}/#{@slos}[@Binding = '#{@post}']/@Location"s
-  @signing_keys_selector ~x"//#{@entdesc}/#{@idpdesc}/#{@keydesc}[@use != 'encryption']"l
-  @enc_keys_selector ~x"//#{@entdesc}/#{@idpdesc}/#{@keydesc}[@use = 'encryption']"l
-  @cert_selector ~x"./ds:KeyInfo/ds:X509Data/ds:X509Certificate/text()"s
+
+
+  defp entity_by_id_selector(id), do: ~x"/#{@entsdesc}/#{@entdesc}[@entityID = '#{id}'][1]" # TODO some EntityDescriptor are prefixed with "md:"
+  # These functions work on EntityDescriptor element
+  defp sso_redirect_url_selector, do: ~x"/#{@entdesc}/#{@idpdesc}/#{@ssos}[@Binding = '#{@redirect}']/@Location"s
+  defp sso_post_url_selector, do: ~x"/#{@entdesc}/#{@idpdesc}/#{@ssos}[@Binding = '#{@post}']/@Location"s
+  defp slo_redirect_url_selector, do: ~x"/#{@entdesc}/#{@idpdesc}/#{@slos}[@Binding = '#{@redirect}']/@Location"s
+  defp slo_post_url_selector, do: ~x"/#{@entdesc}/#{@idpdesc}/#{@slos}[@Binding = '#{@post}']/@Location"s
+  defp nameid_format_selector, do: ~x"/#{@entdesc}/#{@idpdesc}/#{@nameid}[1]/text()"s # TODO for now [1].
+  defp signing_keys_in_idp_selector, do: ~x"./#{@idpdesc}/#{@keydesc}[@use != 'encryption']"l
+  defp cert_selector, do: ~x"./ds:KeyInfo/ds:X509Data/ds:X509Certificate/text()"s
 
   @type id :: binary()
 
@@ -121,9 +125,9 @@ defmodule Samly.IdpData do
   end
 
   @spec load_metadata(%IdpData{}, map()) :: %IdpData{}
-  defp load_metadata(idp_data, _opts_map) do
+  defp load_metadata(idp_data, opts_map) do
     with {:reading, {:ok, raw_xml}} <- {:reading, File.read(idp_data.metadata_file)},
-         {:parsing, {:ok, idp_data}} <- {:parsing, from_xml(raw_xml, idp_data)} do
+         {:parsing, {:ok, idp_data}} <- {:parsing, from_xml(raw_xml, idp_data, opts_map)} do
       idp_data
     else
       {:reading, {:error, reason}} ->
@@ -251,8 +255,8 @@ defmodule Samly.IdpData do
     if is_boolean(v), do: Map.put(idp_data, attr_name, v), else: idp_data
   end
 
-  @spec from_xml(binary, %IdpData{}) :: {:ok, %IdpData{}}
-  def from_xml(metadata_xml, idp_data) when is_binary(metadata_xml) do
+  @spec from_xml(binary, %IdpData{}, %{}) :: {:ok, %IdpData{}}
+  def from_xml(metadata_xml, idp_data, opts) when is_binary(metadata_xml) do
     xml_opts = [
       space: :normalize,
       namespace_conformant: true,
@@ -261,21 +265,51 @@ defmodule Samly.IdpData do
     ]
 
     md_xml = SweetXml.parse(metadata_xml, xml_opts)
-    signing_certs = get_signing_certs(md_xml)
-
-    {:ok,
-     %IdpData{
-       idp_data
-       | entity_id: get_entity_id(md_xml),
-         signed_requests: get_req_signed(md_xml),
-         certs: signing_certs,
-         fingerprints: idp_cert_fingerprints(signing_certs),
-         sso_redirect_url: get_sso_redirect_url(md_xml),
-         sso_post_url: get_sso_post_url(md_xml),
-         slo_redirect_url: get_slo_redirect_url(md_xml),
-         slo_post_url: get_slo_post_url(md_xml),
-         nameid_format: get_nameid_format(md_xml)
-     }}
+
+    entityID = case opts[:entity_id] do
+      nil -> # not provided, we assume file has only one EntityDescriptor
+        get_entity_id(md_xml)
+      e ->
+        e
+    end
+
+    entity_md_xml = get_entity_descriptor(md_xml, entityID)
+
+    
+
+    case entity_md_xml do
+      nil ->
+        {:error, :entity_not_found}
+      _ ->
+        signing_certs = get_signing_certs_in_idp(entity_md_xml)
+        IO.puts "Got #{signing_certs |> length} signing_certs from #{entityID}"
+
+        IO.puts "slo_redirect_url:"
+        slo_redirect_url = get_slo_redirect_url(entity_md_xml) |> IO.inspect
+        IO.puts "slo_post_url:"
+        slo_post_url = get_slo_post_url(entity_md_xml) |> IO.inspect
+        IO.puts "sso_redirect_url:"
+        sso_redirect_url = get_sso_redirect_url(entity_md_xml) |> IO.inspect
+        IO.puts "sso_post_url:"
+        sso_post_url = get_sso_post_url(entity_md_xml) |> IO.inspect
+
+        IO.puts "nameid_format:"
+        nameid_format = get_nameid_format(entity_md_xml) |> IO.inspect
+
+        {:ok,
+          %IdpData{
+            idp_data
+            | entity_id: entityID,
+            signed_requests: get_req_signed(md_xml),
+            certs: signing_certs,
+            fingerprints: idp_cert_fingerprints(signing_certs),
+            sso_redirect_url: sso_redirect_url,
+            sso_post_url: sso_post_url,
+            slo_redirect_url: slo_redirect_url,
+            slo_post_url: slo_post_url,
+            nameid_format: nameid_format 
+          }}
+    end
   end
 
   # @spec to_esaml_idp_metadata(IdpData.t(), map()) :: :esaml_idp_metadata
@@ -364,7 +398,7 @@ defmodule Samly.IdpData do
 
   @spec get_nameid_format(:xmlElement) :: nameid_format()
   def get_nameid_format(md_elem) do
-    case get_data(md_elem, @nameid_format_selector) do
+    case get_data(md_elem, nameid_format_selector()) do
       "" -> :unknown
       nameid_format -> to_charlist(nameid_format)
     end
@@ -373,11 +407,10 @@ defmodule Samly.IdpData do
   @spec get_req_signed(:xmlElement) :: binary()
   def get_req_signed(md_elem), do: get_data(md_elem, @req_signed_selector)
 
-  @spec get_signing_certs(:xmlElement) :: certs()
-  def get_signing_certs(md_elem), do: get_certs(md_elem, @signing_keys_selector)
+  #@spec get_signing_certs(:xmlElement) :: certs()
+  #def get_signing_certs(md_elem), do: get_certs(md_elem, signing_keys_selector())
 
-  @spec get_enc_certs(:xmlElement) :: certs()
-  def get_enc_certs(md_elem), do: get_certs(md_elem, @enc_keys_selector)
+  def get_signing_certs_in_idp(md_elem), do: get_certs(md_elem, signing_keys_in_idp_selector())
 
   @spec get_certs(:xmlElement, %SweetXpath{}) :: certs()
   defp get_certs(md_elem, key_selector) do
@@ -385,7 +418,7 @@ defmodule Samly.IdpData do
     |> xpath(key_selector |> add_ns())
     |> Enum.map(fn e ->
       # Extract base64 encoded cert from XML (strip away any whitespace)
-      cert = xpath(e, @cert_selector |> add_ns())
+      cert = xpath(e, cert_selector() |> add_ns())
 
       cert
       |> String.split()
@@ -395,16 +428,16 @@ defmodule Samly.IdpData do
   end
 
   @spec get_sso_redirect_url(:xmlElement) :: url()
-  def get_sso_redirect_url(md_elem), do: get_url(md_elem, @sso_redirect_url_selector)
+  def get_sso_redirect_url(md_elem), do: get_url(md_elem, sso_redirect_url_selector())
 
   @spec get_sso_post_url(:xmlElement) :: url()
-  def get_sso_post_url(md_elem), do: get_url(md_elem, @sso_post_url_selector)
+  def get_sso_post_url(md_elem), do: get_url(md_elem, sso_post_url_selector())
 
   @spec get_slo_redirect_url(:xmlElement) :: url()
-  def get_slo_redirect_url(md_elem), do: get_url(md_elem, @slo_redirect_url_selector)
+  def get_slo_redirect_url(md_elem), do: get_url(md_elem, slo_redirect_url_selector())
 
   @spec get_slo_post_url(:xmlElement) :: url()
-  def get_slo_post_url(md_elem), do: get_url(md_elem, @slo_post_url_selector)
+  def get_slo_post_url(md_elem), do: get_url(md_elem, slo_post_url_selector())
 
   @spec get_url(:xmlElement, %SweetXpath{}) :: url()
   defp get_url(md_elem, selector) do
@@ -425,4 +458,15 @@ defmodule Samly.IdpData do
     |> SweetXml.add_namespace("md", "urn:oasis:names:tc:SAML:2.0:metadata")
     |> SweetXml.add_namespace("ds", "http://www.w3.org/2000/09/xmldsig#")
   end
+
+  @spec get_entity_descriptor(:xmlElement, entityID :: binary()) :: :xmlElement | nil
+  defp get_entity_descriptor(md_xml, entityID) do
+    selector = entity_by_id_selector(entityID)
+    try do
+      SweetXml.xpath(md_xml, selector)
+    rescue
+      _ -> {:error, :entity_not_found}
+    end
+  end
+
 end