[ZDP] Zope Architecture

Martijn Pieters mj@antraciet.nl
Wed, 19 May 1999 14:00:08 +0200

At 12:43 19/05/99 , Tom Deprez wrote:
>Added another picture to chapter II.3. I received this one from Paul.
>Thanks Paul! But, now I'm confused again :-( (sorry!). In this picture, we
>see ZServer... I thought ZServer was Medusa (or ZopeHTTPServer), seems I'm
>wrong again here. What are the tasks of ZServer?

ZServer is _based_ on Medusa, and is a fast architecture for publishing 
Zope. It can accept FTP and HTTP connections, so you can approach it using 
your browser or FTP client. It can also be accessed using PCGI and other 
protocols, so you could in theory place a webserver (like Medusa itself, or 
Netscape Enterprise or Apache), and have it contact ZServer for further 

>It seems that a browser is also capable for entering ZServer... Is this the
>WebDAV? PS. I've IE5 at home... how to use IE5 with WebDav?

No, WebDAV is completely handled by Zope. WebDAV is basically an extension 
to the HTTP/1.1 protocol. It uses some extra HTTP commands, like OPTIONS, 
to implement it's functionality. The problem lies in these extra commands. 
Most webservers block any command they don't recognize, instead of 
propagating the command to Zope, thus breaking WebDAV. Even Apache needs a 
small patch (if incorporated into the official Apache distribution, future 
versions of Apache will support Zope WebDAV).

IE5 includes a technology called Web Folders. This basically extends the 
Windows Explorer to support remote 'Folders', as if they were local. It 
uses either the Frontpage Extensions protocol (as used in Frontpage) or the 
WebDAV protocol to access the remote files, and create the directory views. 
You can open a Zope server URL as a Web Folder by using the File|Open 
command of IE5.0 and checking the 'Open As Web Folder' checkbox.

One big disadvantage of WebDAV is that files are still retrieved trhough 
the web using the old GET command, meaning you don't get the raw DTML from 
the server, but the rendered version that you get in the browser. WebDAV 
does provide for a source-link property on objects to find out where to get 
the source of an object, but Zope nor IE5.0 support this (yet).

>What are LDAP, IMAP for what can they be used?

LDAP stands for Lightweight Directory Access Protocol. It's used for 
simplified Directory access, and is derived from X.500, the heavyweight. 
For more information, see the LDAP FAQ:

A Directory is usually a database optimized for read-access, that stores 
it's data in a hierarchical structure. It is usually used for storing data 
about people and organizations, and providing a central database for 
enterprise wide logins.

LDAP is often used in email clients to find out email address of people, 
for example within your organization. I see you are using Eudora Light 3.0. 
If you upgrade to version 4.0, you can start using it immediately, because 
Eudora supports LDAP, and uses it to query central email databases like 
Bigfoot (http://www.bigfoot.com) and Switchboard (http://www.switchboard.com/).

IMAP stands for Internet Mail Access Protocol. It is a protocol used 
for  accessing electronic mail, kept on a central mail server. In other 
words, it  allows an email program to access remote messages as if they 
were local. You basically manage all your email on a central server, 
including creation and moving of folders. More info on this at 

DC is working on building LDAP and IMAP support into Zope. With this, you 
could for example build a Zope interface to an IMAP server, basically 
creating your own HotMail. Or you could authenticate users against a LDAP 
Directory server. You could use a LDAP server in much the same way as a 
relational database, giving web users access to the data contained within.

A good place to get your questions answered, is by using the excellent 
Search Engine/Directory of Netscape, called the Open Directory  Project:

It's contents are maintained in an Open Source manner, by over 11.000 
editors. Your's truly is editor of the Zope topic, and it's subtopics.

Martijn Pieters, Web Developer
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