The OpenACS and LAMP represent approaches to developing large scale web enabled database applications. Both have a very strong track record of enabling developers to quickly and efficiently build websites with complex functionality while still maintaining high performance. The are significant differences between the two, however. This article attempts to address these differences and why the OpenACS is a preferred approach to developing scalable, complex web applications.
Note: This article assumes the use of a Unix-oriented operating system for both toolkits such as Linux, FreeBSD or Solaris. The use of Microsoft Windows is outside the scope of the discussion.
The OpenACS is a framework for developing web applications. It is characterized by a specific set of components around which a group of developers have spent nearly 10 years developing a stable data model and a set of business logic for reuse in user-oriented, data-centric web applications. A free and open source project released under the GNU General Public License, the OpenACS can be thought of as consisting of four components:
Web Application Server
The OpenACS uses AOLserver, a high performance web application server that has been proven in perhaps the most highly used environments on the web as it runs AOL.com, Netscape.com, MovieFone.com, Mapquest.com and other major web properties. AOLserver is a unique combination of efficient database connection pooling, native database APIs and an easy to use embedded scripting language called Tcl. This collection of features make it a very powerful rapid web development environment.
Relational Database Management System
Originally written for Oracle, the industry leading RDBMS, the OpenACS now uses either Oracle or PostgreSQL, the most advanced open source relational database. Both systems offer excellent performance, stability and features that the OpenACS community leverages to create complex data driven applications. These features include native atomic transactions, foreign key constraints and native procedural languages.
OpenACS Business Logic and Data Model
The truly unique component of the OpenACS is the time tested business logic and data model. These components have been in development and use for nearly 10 years and have seen over $50M of investment in their design, documentation and implementation. The components include a well defined and flexible templating language, extensive user registration, extremely powerful permissioning model and well considered security and authorization mechanisms. In addition, the OpenACS provides mechanisms for data input validation and automated testing among other things. These foundations provide developers with the ability to rapidly create and deploy packages such as forums, portals or a customized application.
The business logic of the OpenACS is written in Tcl, a popular scripting language that is embedded in AOLserver. Tcl is not as popular in the web development world as its "P" cousins, but it is a very well known and extensive scripting language. It is marked by a very shallow learning curve, simple syntax and excellent performance. Used, of course, by AOL for its web properties, Tcl also is heavily used in the networking world (Cisco uses it as the embedded language for its router hardware) and in the automated testing industry.
The OpenACS has a large, focused and committed community of developers and users. The community consists of individuals, corporate vendors and institutional users. Some of the users include very influential organizations such as Greenpeace International, MIT's Sloan School of Management and the E-LANE consortium - a group of organizations in Latin and Spanish speaking nations collaborating as part of a grant from the European Union. Openacs.org is the nexus for this community to develop new tools, share experience and assist one another.
Support, training, and documentation are typical points of comparison between open-source and proprietary platforms, and rightly so. In this comparison, OpenACS comes out quite well in many areas. In some cases, users have assessed the level of support and basic documentation available for free from the community as superior to that from commercial vendors or from other open-source systems.
The LAMP approach to web development is similar in scope but a different approach than the OpenACS. While the OpenACS is a framework that has a specific standard and focus, LAMP is far more open and represents many different approaches.
Apache is perhaps the most successful open source software project in the industry, running nearly two thirds of the sites on the web. It has proven itself in very demanding environments as a stable and flexible tool. It focuses on performing a single task, namely the processing of requests from web clients.
MySQL is a popular free and open source database that has gained recognition for its friendly slant towards new developers and for its performance. It is well documented and has been used in many web applications and web sites.
The final component of a LAMP system is a scripting language such as Perl, PHP or Python. Each language has a passionate and well developed community. They are all well documented and have a excellent track records where they have been used to deploy systems. Each has a module that acts as a web application server for Apache (e.g. mod_perl). Each language has a number of application frameworks that are independent but can be connected to one another fairly easily. For instance, Drupal can be connected with phpBB and OScommerce to create a CMS, bulletin board and ecommerce website.
The LAMP community is indeed very large. There is a great number of books and websites dedicated to explaining how to use various components to create an application. Orielly's onLAMP.com is one such resource.
The sheer number of companies, individual developers and other resources makes the LAMP platform secure in its longevity. A customer will not have a difficult time finding developers who are familiar with its components or developers who can become familiar with the components quickly.
AOLserver vs Apache
The comparison of AOLserver and Apache is probably better explained as the comparison of AOLserver and Apache+mod_perl+mod_dbi. In other words, AOLserver's is a clean and simple integration of the equivalent of three separate Apache products - the web server, the application server and the database connector. In addition, AOLserver's multi-threaded architecture and database connection pooling provides very efficient performance in data intensive applications.
For instance, AOL uses AOLserver in their largest properties to process requests millions of simultaneous, data intensive requests. With a very simple Tcl script calling native database APIs that can access the first available database connection in the pool, AOL can easily manage sites like Moviefone.com, DigitalCities.com and Mapquest.com
Apache plus an application server module can certainly manage a similarly large site as many have proven. However, the administrative overhead of running multiple services is not as elegant as the AOLserver architecture. There are those, however, that prefer such a separation of web and application server in what is called a "multi-tiered architecture."
The OpenACS community believes that the efficiency gains - in terms of stability, performance and administrative ease - of an integrated web application server we've never felt the attraction of migrating to Apache.
PostgreSQL or Oracle vs MySQL
MySQL is perhaps the most popular open source SQL database in the free and open source software world. It is marked by being very well documented, tested in various real world applications and excellent performance for web applications. The community is quite healthy and the database seems to be improving.
The OpenACS was originally developed for Oracle and so it relies heavily on database features that only recently MySQL has begun to address. These features include native transaction atomicity (that is, a command is either completed or it is not - there is no halfway), foreign keys (data that is related to another table is consistent and that consistency is always enforced) and a procedural language which assists in the writing of complex data queries. It has always been the opinion that these items, in addition to others, are so critical for the integrity of the data of the application that we will not use MySQL until all of them have been implemented as first class features.
However, MySQL has achieved a great deal of popularity despite what we consider to be serious limitations. This popularity is due to the fact that MySQL has performed exceedingly well when developers have written applications that compensate for such shortcomings, in cases where the data stored is transient or data integrity is not as critical a characteristic for the application as performance.
Luckily, there is another free and open source database called PostgreSQL that not only conforms to the principles that the OpenACS community considers critical but has proven to be as performant as MySQL in real world scenarios. It has native transaction atomicity, supports foreign keys and has a number of procedural languages to choose from, including one that is a clone of Oracle's (which helps us maintain support for both databases.) PostgreSQL also continues to prove itself in demanding environments, including running the .ORG and .INFO registries.
As a result, we feel that in using PostgreSQL for the OpenACS, we have the best of both worlds - a free and open source database that is high performance and flexible while providing us with first-class data security and integrity.
(As a note, MySQL does have support for transactions and foreign keys with an external module called InnoDB. But these features are not turned on by default and they are not native. MySQL 5 promises to change both flaws, but it is not suitable for production use at this time, neither does it fix the absence of a quality procedural language..)
The OpenACS Business Logic and Data Model vs Perl/PHP/Python
This is perhaps the most difficult comparison to make because the items are not the same. The OpenACS is a framework that is written in Tcl because AOLserver is an excellent product that happens to have Tcl as an embedded scripting language. LAMP applications are often written because the developers' have a preference for Perl, PHP or Python.
The best comparison that can be made, then, is which approach provides the most consistency, stability and maintainability for the developers. The OpenACS is a foundation upon which complex applications can be built using a shared data model and reuse of standard components like a templating system, workflow and content repository. Most importantly, the permissioning infrastructure provides a way to design, build and administer secure data driven applications.
There are many similar applications in the LAMP world (Drupal, BinaryCloud, Midgaard, Typo3) but none of them have the track record or the fundamentally sound data model as the OpenACS. Furthermore, each only addresses part of the problem, either as a content management system, as a bulletin board application or an ecommerce package.
As a result, developers in the LAMP world often find themselves developing from first principles over and over again. This means that each time they develop a new system, they design the basic data model for user registration, authentication, content management, etc and then begin gluing different tools together. Even with excellent code repositories like CPAN for Perl for Perl or PEAR for PHP these efforts are usually ad hoc. They also lack a permissioning infrastructure that can manage the overall security of the application.
For instance, taking a content management system like Drupal, a bulletin board system like phpBB and an ecommerce package like OScommerce, each of which is extremely well built in their own right, but the developer must design a way to share each respective application's idiosyncratic data representation.
The OpenACS' shared data model, templating system and service oriented model allows for developing such a system much easier. The standard data model, presentation code and information processing facilities allows the developer to quickly cobble together a stable, powerful and maintainable application. Most importantly, the well designed and tested permissioning infrastructure allows developers to build very flexible and secure data-driven applications.
OpenACS vs LAMP communities
The LAMP community as a whole certainly dwarfs the OpenACS community. Considering that LAMP represents an approach including three or four languages vs the OpenACS which is a focused community, this is not surprising.
This is certainly a strength of LAMP. The fact that it is very simple to find developers who are familiar with each tool rather than a framework is something that a user should consider when selecting a software tool. The plentiful documentation is also extremely heartening.
The OpenACS community, however, is very successful and flourishing. There are over 25 international institutions that have deployed .LRN, the free and open source course management system. There are over 20 vendors listed on the OpenACS.org home page offering commercial support. The OpenACS forums and IRC channel is very active as developers discuss ways to enhance the framework.
The LAMP approach includes hundreds or thousands of different platforms. What this means for any specific LAMP solution is that it may draw from a broader library of other programs, but the list of actually tested, integrated pieces and of dedicated developers may be much smaller. LAMP developers are fragmented across many projects, but OpenACS holds the lions share of attention for its technologies and resists community splintering remarkably well.
While the LAMP community is much larger, the OpenACS has established itself in a community of users where technical proficiency and stability is most important. Due to and for this reason, the OpenACS community is vibrant and healthy.
The author would like to thank the following people for helping with this document: Joel Aufrecht, Dave Bauer, Carl Blesius, Cesar Brea, Bruno Mattarollo and Alfred Werner.
Copyright (c) 2004 Talli Somekh
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".