Created Manual::About (INCOMPLETE, just a stub now)

[catagits/Catalyst-Runtime.git] / lib / Catalyst / Manual / About.pod

=head1 NAME

Catalyst::Manual::About - Basic explanation of Catalyst

=head1 DESCRIPTION

This document is a basic introduction to the I<why> of Catalyst. It does
not teach you how to write Catalyst applications; for an introduction to
that please see L<Catalyst::Manual::Intro>. Rather, it explains the
basics of what Catalyst is typically used for, and why you might want
to use Catalyst to build your applications.

=head2 What is Catalyst? The short summary

Catalyst is a web application framework. This means that you use it to
help build applications that run on the web, or that run using protocols
used for the web. Catalyst is designed to make it easy to manage the
various tasks you need to do to run an application on the web, either by
doing them itself, or by letting you "plug in" existing Perl modules
that do what you need. There are a number of things you typically do
with a web application, for example:

=over 4

=item * Interact with a web server

If you're on the web, you're relying on a web server, a program that
sends files over the web. There are a number of these, and your
application has to do the right thing to make sure that your data works
with the web server you're using. If you change your web server, you
don't want to have to rewrite your entire application to work with the
new one.

=item * Do something based on a URI

So that C<http://www.mysite.com/catalog/view/23> will go to a "view" of
item 23 in your catalog, and C<http://www.mysite.com/order_status/7582>
will display the status of order 7582, and
C<http://www.mysite.com/add_comment/?page=8> will display a form to add
a comment to page 8.

=item * Interact with a data store

You probably use a database to keep track of your information. Your
application needs an easy way to interact with your database, so you can
create, edit, and retrieve your data.

=item * Handle forms

When a user submits a form, you process it, and make sure it's been
filled in properly, and then then do something based on the
result--submitting an order, updating a record, sending e-mail, or going
back to the form if there's an error.

=item * Display results

You have an application running on the web, people need to see
things. You usually want to display things on a web browser; you will
probably be using a template system to help generate HTML code; you
might need other kinds of display, such as PDF files or RSS feeds.

=item * Manage users

You might need the concept of a "user", someone who's allowed to use
your system, and is allowed to do certain things only. Perhaps normal
users can only view or modify their own information; administrative
users can view or modify anything; normal users can only order items for
their own account; normal users can view things but not modify them;
order-processing users can send records to a different part of the
system; and so forth. You need a way of ensuring that people are who
they say they are, and that people only do the things they're allowed to
do.

=item * Develop the application itself

When you're writing or modifying the application, you want to have
access to detailed logs of what it is doing. You want to be able to
write tests to ensure that it does what it's supposed to, and that new
changes don't break the existing code.

=back

Catalyst makes it easy to do all of these tasks, and many more. It is
extremely flexible in terms of what it allows you to do, and very fast.
It has a very large number of "plugins" that interact with existing Perl
modules so that you can easily using them from within your application.

=head3 What B<isn't> Catalyst?

Catalyst is not an out-of-the-box solution that allows you to set up a
complete working e-commerce application in ten minutes. (There are,
however, several systems built on top of Catalyst that can get you very
close to a working app.) It is not designed for end users, but for
working programmers.

=head2 Some background

=head2 The MVC pattern

=head1 AUTHOR

Jesse Sheidlower, C<jester@panix.com>

=head1 SEE ALSO

L<Catalyst>, L<Catalyst::Manual::Intro>

=head1 COPYRIGHT

This program is free software, you can redistribute it and/or modify it
under the same terms as Perl itself.