Clarify things around the drafts

Author: mdboom

source/basics.rst

@@ -107,6 +107,8 @@ you control, for example::
 
 The details of `id` become more apparent when you start `structuring`.
 
+|draft6|
+
 .. draft_specific::
 
     --Draft 4

source/conventions.rst

@@ -35,6 +35,27 @@ JSON in a few different languages:
     For C, you may want to consider using `Jansson
     <http://www.digip.org/jansson/>`_ to read and write JSON.
 
+Draft-specific notes
+--------------------
+
+The JSON Schema standard has been through a number of revisions or "drafts". The
+most important are Draft 6, the most recent at the time of this writing, and
+Draft 4, on which a lot of production software was built, and the draft for
+which an earlier version of this book was written.
+
+The text is written to encourage the use of Draft 6 and gives
+priority to the latest conventions and features, but where it differs from Draft
+4, those differences are highlighted in special call-outs. If you only wish to
+target Draft 6, you can safely ignore those sections.
+
+|draft6|
+
+.. draft_specific::
+
+   --Draft 4
+   This is where anything pertaining to an old draft would be mentioned.
+
+
 Examples
 --------
 

source/index.rst

@@ -24,7 +24,7 @@ validator---just yet.
 
 .. note::
 
-    This book describes JSON Schema draft 4. The most recent version is draft 7
+    This book describes JSON Schema draft 6. The most recent version is draft 7
     --- stay tuned, updates are coming! Earlier and later versions of JSON Schema
     are not completely compatible with the format described here.