MMBase Architectural Overview
Bridge (or the MMBase Connection Interface)
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Table of Contents
MMBase is a general purpose object oriented content management system, which is implemented in Java. MMBase operates as a web-application which can be plugged-in at an application server like Tomcat, Orion, Resin, WebSphere, Jetty or IIS.
The main difference between a webserver like Apache and an application server is that an application server is capable of executing server-side functionality like programs written in Java. The application servers on which MMBase can be plugged in have to support Java and Java Server Pages.
This document provides an overview of the MMBase architecture. Each component in the architecture is described. Suggestions for further reading are given. The MMBase architecture can be subdivided into the following layers.
Database Access
MMBase Core
Security
Bridge
Plugins
MMBase is connected to a database via the JDBC interface. MMBase 1.6 supports the following relational databases.
Informix
PostgreSQL
MySQL
HSQL
Oracle
DB2
A number of features of the MMBase Database layer are:
Database transparency
Ones you've created a database and connected it to MMBase, MMBase will do the rest for you. It will take care of the creation of tables and will generate and take care of link tables. So the only SQL statements which you have to learn to being able to work with MMBase are: creating a database, making a backup of a database, restoring a database and dropping a database.
Automatic index generation
When MMBase fills your database with tables it automatically creates indices for columns, which are known to be frequently used in database queries. This will guarantee that the database layer operates in an efficient way right from the start.i
[TO DO: what do we have to say about Query and Storage? ]
MMBase is an object oriented content management system. Content is stored in objects. Objects can be connected to other objects by relations. These relations are also objects, which can also contain content. Next to containing content, objects can also have functionality. E.g. the image object has the functionality to convert and scale images. The MMBase Core provides the mapping from the relational database layer to the object oriented layer. It is capable of:
configuring objects and relations.
MMBase objects are configured by XML-configuration files called builders. These builders describe the fields an object has and its functionality. The field names for use in the Graphical User Interfaces can be stored in multiple languages to make your MMBase implementation ready for use in different languages. After a builder is placed in the MMBase installation, the corresponding table in the database is automatically created. To learn more about using builders check out the Administrators/MMBase Builder Configuration documentation . In the MMBase standard builders document under the Templaters and Designers section you can find info on the builders shipped with the MMBase release.
[TO DO: should both builder docs not be in the same section ? ]
creating objects and relations.
When an object, or node, is created the functionality added to the object can dictate that some action has to be taken. E.g. an email which is stored in MMBase is posted.
The creations of relations is a four-step procedure:
Create a builder with the fields that are necessary in the relation.
Add the relation to the list of relation definitions (RelDef)
Enter the source-relation-destination information into the list of relations types (TypeRel)
Create relations.
See the document on relations in the Information Analysts section for more information on this topic.
updating objects and relations.
MMBase contains observers that listen to changes in objects and relations. When a change occurs, an observer can carry out some appropriate actions. Most observers are used to keep the MMBase caches up to date. Examples of such MMBase caches are the cache with converted images and the query cache.
retrieving objects and relations.
When retrieving information from the database, MMBase will store the results of the database queries for future use. This cache functionality helps to speed up performance. Next to caches for database queries, MMBase also contains a cache for storing converted images for future use. These caches are totally transparent.
[TO DO: write document on Transactions and Multicast.]
MMBase offers an elaborated security layer for authorization and authentication. Authorization tells what a user is allowed to do. Authentication tells how a user can log on to an MMBase website. The security models available in MMBase 1.6 are:
Cloud Security
MMBaseusers are administrated in the MMBase object cloud. This security model offers a basic ranking system in Anonymous, Users and Admin.
An advantage of the Cloud Security are that you can do your user administration via the webinterface and that you are able to integrate the MMBase users into your object model.
Context Security
MMBase users are administrated in XML-configuration files on the file system. Users are part of Groups and Ranks. Each object in MMBase belongs to a context. The Context Security model offers an fine-grained mechanisms to specify rights of users and groups in different contexts. The model provides the possibility to define basic workflow schemes.
The Context Security is especially fit if the rights of users has to be specified on object level or if you need basic workflow functionality. A drawback of the context security model is that the user administration can not be carried out via the web interface, but one has to use the XML-configuration files.
Context Cloud Security
The Context Cloud Security provides the same functionality as the Context Security. In contrast to the Context Security, the Context Cloud security stores the authentication and authorization information in the object cloud.
The Context Security is especially fit if the rights of users has to be specified on object level or if you need basic workflow functionality. A drawback of the context security model is that the user administration can not be carried out via the web interface, but one has to use the XML-configuration files.
Basic Security
Provides the basic login functionality, where users are administrated in an file on the file system.
This security model should only be used in combination with MMBase releases before version 1.5, that operate on basis of SHTML.
No security
Although trivial, it is sometimes handy to have an MMBase installation with no authentication, no authorization or no security at all. It won't come as a surprise that MMBase supports this functionality.
To learn more about security see the The MMBase Security Framework, Installing and using Context Security, Installing and using Cloud Security in the Administrator section.
The MMBase Connection Interface handles the requests from the MMBase Plugins and passes them to the Security layer. See the Bridge (MMCI) API documentation under Templaters and Designers for more information on this topic.
There exist a growing list of plugins which add functionality to the MMBase Core. The most important plugins are listed below.
Taglib
The taglib provides a set of tags which facilitate communication between MMBase and JSP-templates. See the MMBase taglib reference and the Creating webpages with the MMBase Tag Library in the Templaters and Designers section.
One widely used tool build with the taglib are the JSP-editors for MMBase. With MMBase 1.6 to versions of the JSP-editors are included \mmeditors\jsp and \mmexamples\jsp\my_editors .
Dove
Dove facilitates communication between MMBase and XML-files. You can use Dove to build dynamic MMBase websites based on XML and XSLT. See the Dove XML API under the section developers to learn more about this topic.
An important application that uses Dove are the MMBase editwizards. The editwizards let you create task-oriented user-friendly forms, which can be a big help for editors in working with MMBase. See the Editwizards documentation under the Templaters and Designers section for more information on creating and using editwizard forms.
R-MMCI
The Remote MMBase Cloud Interface makes it possible to communicate with different MMBase installation at the same time. This powerful plugin makes it possible to share and exchange data between MMBase installations irrespective of their location. See the Remote MMBase Cloud Interface under the section Developers to find out more.
XML-importer
The XML-importer can be used to import data from XML-files into MMBase. The XML-importer provides intelligent Find and Merge scenario's. More information can be found in the XML Importer (TCP 2.0) documentation in the Developers section.
Applications
The Applications plugin provide the functionality to package MMBase websites. See the MMBase Applications documentation under the Administrator section for more information on this item.
Editwizards
The editwizards provide the functionality to define forms to edit the MMBase object cloud. Editors who do not frequently use MMBase might get lost in their MMBase object cloud, when using the default JSP editors to enter or change content, With the editwizards it is possible to build task oriented forms, which guide editors through their work. See the editwizard userguide and reference manual in the templaters section for more information on the editwizards.
This is part of the MMBase documentation.
For questions and remarks about this documentation mail to: documentation@mmbase.org