rework BasicConstraints and Extension.
diff --git a/docs/x509.rst b/docs/x509.rst
index 8024258..7eb47a3 100644
--- a/docs/x509.rst
+++ b/docs/x509.rst
@@ -280,7 +280,11 @@
.. versionadded:: 0.9
- All X.509 extensions are registered against this interface.
+ .. attribute:: oid
+
+ :type: :class:`ObjectIdentifier`
+
+ The attribute OID.
.. attribute:: critical
@@ -288,13 +292,18 @@
Determines whether a given extension is critical or not.
+ .. attribute:: value
+
+ Returns an instance of the extension type corresponding to the OID.
+
.. class:: BasicConstraints
.. versionadded:: 0.9
- Basic constraints is an X.509 extension that defines whether a given
+ Basic constraints is an X.509 extension type that defines whether a given
certificate is allowed to sign additional certificates and what path
- length restrictions may exist.
+ length restrictions may exist. It corresponds to
+ :data:`OID_BASIC_CONSTRAINTS`.
.. attribute:: ca