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<h1>Chapter 1: Introducing Zope</h1>
<p> This chapter explains what Zope is and who it's for. It describes in
broad strokes what you can do with Zope. You also learn about the
differences between Zope and other web application servers.</p><h2> What Is Zope?</h2>
<p> Zope is a framework for building web applications. A web application
is a computer program that users access with a web browser over the
Internet. You can also think of a web application as a dynamic web
site that provides not only static information to users but lets them
use dynamic tools to work with an application.</p><p> Web applications are everywhere, and web users work with them all the
time. Common examples of web applications are sites that let you
search the web, like <em>Yahoo</em>, collaborate on projects, like
<em>SourceForge</em>, or communicate with other people over e-mail, like
<em>HotMail</em>. All of these kinds of applications can be developed with
Zope.</p><p> So what do you get when you download Zope? You actually get a lot of
things. Zope consists of several different components that work
together to help you build web applications. Zope comes with:<dl>
<dt> A Web server</dt>
<dd>Zope comes with a built in web server that
serves content to you and your users. Of course, you may
already have an existing web server, such as <em>Apache</em> or
<em>Microsoft IIS</em> and you may not want to use Zope's. Not to
worry, Zope works with these web servers also, and any other web
server that supports the Common Gateway Interface (CGI).</dd>
<dt> A Web based interface</dt>
<dd>When you build web applications with Zope,
you use your web browser to interact with the Zope <em>management
interface</em>. This interface is a development environment that lets
you do things like create web pages, add images and documents,
connect to external relational databases and write scripts in
different languages.</dd>
<dt> An object database</dt>
<dd>When you work with Zope, you are mostly working
with objects that are stored in Zope's object database. Zope's
management interface provides a simple, familiar way to manage
objects that resembles the way many common file managers work.</dd>
<dt> Relational integration</dt>
<dd>You don't have to store your
information in Zope's object database if you don't want to,
because Zope works with other relational databases such as
<em>Oracle</em>, <em>PostgreSQL</em>, <em>Sybase</em>, <em>MySQL</em> and many others.</dd>
<dt> Scripting language support</dt>
<dd>Zope allows you to write web
applications in a number of different languages, like
<a href="http://www.python.org/">Python</a>, <a href="http://www.perl.org/">Perl</a>, and
Zope's own Document Template Markup Language (DTML).</dd>
</dl>
</p><p> These are just some of the compelling features that have made Zope so
popular for developing web applications. Perhaps Zope's best feature
of all is its friendly, open source license. This means that not only
is Zope free of cost for you to download, but you are also free to use
Zope in your own products and applications without paying royalties or
usage fees. Zope's open source license also means that all of the
"source code" for Zope is available for you to look at, understand, and
extend. Zope does not lock you into a proprietary solution that could
hold you and your web users hostage.</p><p> From a business perspective, there are three key ideas to understanding
what Zope can do for you: powerful collaboration, simple content
management, and web components. The following sections are mostly
oriented towards business people making decisions about Zope, so if you
are interested in jumping right in, skip to the next chapter, <em>Using
Zope</em>.</p><h2> Powerful Collaboration</h2>
<p> Years ago, Zope's core technologies were designed by Zope Corporation
for an Internet Service Provider that provided web pages
for newspapers. These newspapers in turn wanted to provide web
pages for <em>their</em> customers. To scale in this environment, Zope
was designed to safely delegate control to different groups of
users at any level in the web site. Safely delegating control
means considering these things:<ol>
<li> Presenting information in an easy to understand way. Most people
understand clicking on folders better than issuing database
commands, so Zope uses an interface that resembles a simple file
manager, like <em>Microsoft Windows Explorer</em> and other popular
file managers.</li>
<li> Command line tools can be difficult to use and people are
generally more comfortable using web browsers, so Zope was
designed to be used almost exclusively through a web browser.</li>
<li> Collaborative environments require tools to allow users to recover
from their mistakes and to work without interfering with each
other, so Zope has Undo, Versions, and other tools to help
people work safely together.</li>
</ol>
</p><p> These features make Zope an ideal environment for programming and
authoring web content by groups and sub-groups of users.</p><h2> Simple Content Management</h2>
<p> Many web applications are traditionally built in three layers. Data
and other information is stored in databases, the programs that drive
the behavior of the application are stored in files in one location,
and the HTML and other layout and presentation information is stored
somewhere else.</p><p> While this has advantages, it also has disadvantages. Different
kinds of tools and expertise must be used to work with the different
components. All the different components may need to have their own
kind of security and maintenance concerns. Many of these kinds of
tools are not manageable from a web browser or from simple command
line or GUI tools like FTP.</p><p> In Zope, all of these components are brought together into one
coherent system. All require a common set of services: security,
web-based management, searching, clustering, syndication and others.
By bringing together all of these concepts into one manageable
system, Zope enables you to use one set of skills and one set of
tools to develop complex web applications. In addition, centralizing
our model means Zope can more easily work with other external tools,
like relational databases, GUI web editors, and other systems that
can inter-operate with Zope.</p><h2> Web Components</h2>
<p> The Web is a growing, dynamic platform. The web has evolved enough
standards and APIs that creators of services, products, and
technology can think in terms of the web as an architectural model
to develop their applications around, instead of just a means of
distributing static HTML documents to users.</p><p> Evidence of this is sprouting up in many locations. Microsoft's
<em>.NET</em> architecture envisions a world of web components running on
remote systems, providing specific services to applications around
the world. <em>Frontier</em>, by UserLand Software, pioneered a simple
web services protocol called XML-RPC to allow web components to
communicate with each other (Zope also works with XML-RPC, which
is discussed in Chapter 10, "Advanced Zope Scripting"). With web
components, the model of a person sitting in front of the browser
is no longer the only model of the web.</p><h2> Zope History</h2>
<p> In 1996 Jim Fulton, the CTO of Zope Corporation and Python guru, was
drafted to teach a class on CGI programming, despite not knowing much
about the subject. Jim studied all of the existing documentation on
CGI on his way to the class. On the way back from the class, Jim
considered what he didn't like about traditional CGI based programming
environments: its fragility, lack of object-orientation, and how it
exposes web server details. From these initial musings, the core of
Zope was written on the plane flight back from the class.</p><p> Zope Corporation went on to release three open source software
packages to support web publishing, <em>Bobo</em>, <em>Document Template</em>,
and <em>BoboPOS</em>. These package were written in Python. They have
evolved into core components of Zope providing the web ORB (Object
Request Broker), DTML scripting language, and object
database. Zope is still mostly written in Python with a few
performance-critical sections in C.</p><p> Back then, Zope Corporation had developed a commercial
application server based on their three open source components.
This product was called <em>Principia</em>. In Novermber of 1998,
investor Hadar Pedhazur convinced Zope Corporation to open
source Principia. This became Zope, which was given its own home
at <a href="http://www.zope.org/">Zope.org</a>.</p><h2> Who Can Benefit from Zope?</h2>
<p> It takes a lot of people working together to create web services.
To manage and coordinate these people on large-scale sites can be
a difficult task. We've identified some common roles in this
scenario to be aware of:<ul>
<li><em>Consumers</em> use the site to locate and work with useful content.</li>
<li><em>Business Users</em> create and manage the site's content.</li>
<li><em>Site Designers</em> create the site's look and feel.</li>
<li><em>Site Developers</em> program the site's services.</li>
<li><em>Component Developers</em> create software intended for distribution.</li>
<li><em>Administrators</em> keep the software and environment running.</li>
<li><em>Information Architects</em> make platform decisions and keep track
of the big picture.</li>
</ul>
</p><p> Zope is a platform upon which Site Developers create services to be
turned over to Site Designers and Business Users, and Component
Developers distribute new products and services for Zope users world
wide.</p><p> Zope can install Zope products that are focused on different
audiences. For instance, <em>Squishdot</em> is a popular weblog, written
in Zope, that is useful right out of the box. Squishdot users
won't necessarily see that Zope is underneath. Other Zope
products, such as Zope Corporation's <a href="http://cmf.zope.org">Content Management
Framework</a>, take the same approach,
targeting audiences that need not know of Zope's existence
underneath.</p><h2> How Can You Benefit From Zope?</h2>
<p> We've looked at the Zope philosophy and architecture, now let's
survey some of of the applications of Zope. All sites solve
different problems, but many sites tackle a set of common issues
daily. Here are some of the main uses of Zope:<dl>
<dt> To Present Dynamic Content</dt>
<dd>You want to tailor your web site's
presentation to its users, integrate information in databases
and provide users with searching. You'd also like to make your
web site automate and facilitate your business processes. Can
your web site react intelligently to visitors in order to
provide a compelling experience? Zope allows you to make every
page dynamic. It comes with facilities for personalization,
integrating information in databases and searching.</dd>
<dt> To Manage your Web Site</dt>
<dd>A small web site is easy to manage,
but a web site that serves thousands of documents, images and
files needs to provide powerful management tools. Can you manage
your site's data, business logic and presentation all in one
place? Can you keep up with your content, or is it getting out
of hand? Zope gives you simple and powerful tools for handling
gigabytes of web content. You can manage your logic,
presentation and data all from your web browser.</dd>
<dt> To Secure Your Web Site</dt>
<dd>When you deal with more than a
handful of web users, security becomes very important. It is
crucial to organize users and be able to safely delegate tasks
to them. For example, folks in your engineering department may
need to be able to manage their web pages and business logic,
designers may need to update site templates, and database
administrators need to manage database queries. Can your system
handle thousands of users, perhaps linked to your existing LDAP
or other user databases with flexible security rules? Zope
allows you to scale your site to thousands of site managers and
millions of visitors. You can simply control security policies
and safely delegate control to others.</dd>
<dt> To Provide Network Services</dt>
<dd>Right now most web sites serve
users, but soon web sites will need to serve remote computer
programs and other web sites. For example, you'd like to make
your news items automatically available to wire service web
sites. Or maybe you want to make products for sale on your site
automatically searchable from a product comparison site. Can
you leverage your existing data and business logic to create
network services or will you have to start over from scratch?
Zope's built-in support for networking makes every Zope site a
network service. Your business logic and data can be accessed
over the web via HTTP and XML-RPC.</dd>
<dt> To Integrate Diverse Content</dt>
<dd>Your content is strewn all over
the place, in relational databases, files, web sites, FTP
archives, XML. Can you unify your data into one coherent
application? Does your system support web standards so that you
can integrate content from legacy systems and new systems that
you will add in the future? Zope supports web standards allowing
you to use your existing data, infrastructure and filesystems.</dd>
<dt> To Provide Scalability</dt>
<dd>So you struck it rich and now you're
getting more hits than you ever imagined. Now you need to handle
a dramatically greater level of traffic than before. Can you
move your site to a different database and server platform and
spread the load across multiple servers? Can your web site grow
to handle your success? Zope allows your web applications to
scale across as many machines as necessary to handle your
load. Zope makes it possible to maintain a small site that can
turn into a huge site overnight based on its "ZEO" technology
(see Chapter 13, "Scalability and ZEO" for more details).</dd>
</dl>
</p><h2> What Zope Gives You</h2>
<p> Let's take a closer look at the Zope features that allow you to
build and manage dynamic web sites.</p><dl>
<dt> Unique Management Environment</dt>
<dd>The first thing you'll notice
about Zope is that it lets you manage your site's data, logic, and
presentation right in your web browser. This means that Zope is
easy to use and is remotely administrable. Zope lets you
collaborate with others to interactively develop your web site.</dd>
<dt> Built-in Tools</dt>
<dd>Zope comes with site management tools, a web
server, a search engine, database connectivity, security and
collaboration services, and more. Out of the box, Zope gives you
everything you need to build a powerful web site.</dd>
<dt> Open Standards Support</dt>
<dd>Zope excels at gluing together diverse
data because of its support for open standards. Zope supports
Internet standards including SQL, ODBC, XML, DOM, FTP, HTTP,
FastCGI, XML-RPC, SOAP, and more.</dd>
<dt> Open Source Licensing</dt>
<dd>With Zope you don't just get an
application, you get the source and a community. Since Zope is
open source you are not held hostage by a single vendor; you're
free to use, distribute and adapt Zope to fit your needs. Zope
also benefits from an active user and developer community. The
community improves Zope's support, audits Zope's security, fixes
bugs, and adds features.</dd>
<dt> Extensibility</dt>
<dd>Zope can be extended in many directions. Third
party applications can be easily created and distributed. The
Zope community has produced hundreds of Zope add-ons for
everything from credit card processing to web discussions.</dd>
</dl>
<h2> Zope Alternatives</h2>
<p> There are many tools available to help you build web
applications. Early in the history of the web, simple web
applications were built almost exclusively with CGI programs
written in Perl or other languages. Now there are a host of
options ranging from open source frameworks like PHP, to
commercial options such as Allaire's Cold Fusion, Java application
servers, and Vignette's Story Server.</p><p> Zope offers a unique mix of features, some similar to, and some very
different from, features offered by other web application tools. Zope
is easy to use, open source, powerful, and provides support for many
different kinds of applications. Here is a short list of common web
tool drawbacks and Zope's advantages:<ul>
<li>Some tools do not offer a simple file manager like user interface,
and are hard to use. Zope has a simple user interface.</li>
<li>Some tools require complex configuration. Zope is easy to install
and requires no configuration before you begin using it.</li>
<li>Some tools require using unfamiliar and proprietary
development tools. Zope works with any standards-compliant
web browser and no other tools will be required to use this
book.</li>
<li>Some tools don't scale as well as Zope does to handle large
numbers of developers and users. Zope has a consistent,
powerful user management system that can scale to many users
with unique, easily managed privileges.</li>
<li>Finally most closed-source, commercial tools don't let you extend,
customize, and redistribute them. Zope is open source.</li>
</ul>
</p><h2> Zope Community</h2>
<p> Zope was one of the first tools of its kind to become open source.
Since opening up the code to Zope, the user base has grown
tremendously.</p><p> The Zope community consists of Zope users and developers. Many of
the community members are professionals such as consultants,
developers and web masters, investing their time and money into
supporting Zope. Others are students and curious hackers, learning
how to use a cool new tool. The community gets together
occasionally at conferences but spends most of its time discussing
Zope on the many Zope mailing lists and web sites. You can find out
more about the many Zope-related mailing lists at
http://www.zope.org/Resources/MailingLists.</p><p> Now that you've learned about Zope's features and history, it's
time to start using it. In the next chapter you'll learn how to
get up and running with Zope. Since Zope is free, you can download
the latest version, and begin working immediately.</p></body>
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