--- lib/A3C.pod	2008/06/19 19:05:26	205
+++ lib/A3C.pod	2008/06/19 19:52:43	207
@@ -12,6 +12,27 @@
 developing and looking into code usage (if it's not documented and tested,
 it doesn't exist) but this part is delivered as pure POD for reading pleasure.
 
+=head1 Models
+
+Models in Jifty are at perl level objects (with validation and
+canonicalization) and tables in database.
+
+For a start, we implement some magic documented in L<A3C::Record> on records
+(rows in database).
+
+Then, we need to mungle data without re-thinking SQL queries which would
+produce same results, so there is L<A3C::SQL> which produce objects that
+look like L<Jifty::Collection>s, but aren't. This allows us to switch into
+SQL in views if needed.
+
+This method is not perfect, and shouldn't be used instead of Jifty models
+just to write SQL because it doesn't do any permission checking. However,
+it's a huge help for compex C<GROUP BY> and C<JOIN> queries which are hard
+to express using L<Jifty::DBI>.
+
+If we needed to generate those queries from within program (from user data,
+for example) something like L<Fey::SQL> would be much better tool.
+
 =head1 LDAP 
 
 Implement LDAP entry and edit interface (insteresting problem since most