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=over

=item *

data sources         (tables and joins),

=item *

database statements  (stateful objects representing stepwise building
                      of an SQL query and stepwise retrieval of results),

=item *

data rows            (lightweight hashrefs containing nothing but column
                      names and values)

=back 

=item *

simple syntax for joins, with the possibility to override default
INNER JOIN/LEFT JOIN properties, and with clever usage of Perl
multiple inheritance for simultaneous access to the methods of all
tables that participate in that join

=item *

nested, cross-database transactions

=item *

choice between 'single-schema' mode (default, more economical) 
and 'multi-schema' mode (optional, more flexible, but a little
more costly in memory)

=back


=head2 Limitations

Here are some limitations of C<DBIx::DataModel>, in comparison
with other Perl ORMs :

=over

=item no schema versioning

C<DBIx::DataModel> knows very little about the database
schema (only tables, primary and foreign keys, and possibly
some columns, if they need special 'Types'); therefore
it provides no support for schema changes (and seldom
needs to know about them).

=item no object caching nor 'dirty columns'

C<DBIx::DataModel> does not keep track of data mutations
in memory, and therefore provides no support for automatically
propagating changes into the database; the client code has to
explicitly manage C<insert> and C<update> operations.

=item no 'cascaded update' nor 'insert or update'

Cascaded inserts and deletes are supported, but not cascaded updates.
This would need 'insert or update', which is not supported.

=back


=head1 INDEX TO THE DOCUMENTATION

Although the basic principles are quite simple, there are many
details to discuss, so the documentation is quite long.
In an attempt to accommodate for different needs of readers,
the documentation has been structured as follows :

=over

=item * 

The L<DESIGN|DBIx::DataModel::Doc::Design> chapter covers the
architecture of C<DBIx::DataModel>, its main distinctive features and
the motivation for such features; it is of interest if you are
comparing various ORMs, or if you want to globally understand
how C<DBIx::DataModel> works, and what it can or cannot do.
This chapter also details the concept of 
L<statements|DBIx::DataModel::Doc::Glossary/"STATEMENT OBJECTS">.


=item *

The L<QUICKSTART|DBIx::DataModel::Doc::Quickstart> chapter
is a guided tour that 
summarizes the main steps to get started with the framework.

=item *

The L<REFERENCE|DBIx::DataModel::Doc::Reference> chapter
is a complete reference to all methods, structured along usage steps :
creating a schema, populating it with table and associations,
parameterizing the framework, and finally data retrieval and
manipulation methods.

=item *

The L<COOKBOOK|DBIx::DataModel::Doc::Cookbook> chapter
provides some recipes for common ORM tasks.

=item *

The L<INTERNALS|DBIx::DataModel::Doc::Internals> chapter
documents the internal structure of the framework, for programmers
who might be interested in extending it.


=item *

The L<GLOSSARY|DBIx::DataModel::Doc::Glossary> 
defines terms used in this documentation,
and points to the software constructs that
implement these terms.

=item *