ACS 4 Kernel Documentation

by Pete Su

Introduction

Compared to its predecessors, version 4 of the ArsDigita Community System (ACS) has a much more structured organization, i.e. the most significant change is found at the system architecture level, reflected in the following hierarchy:

• The ACS 4 Kernel, which handles system-wide necessities such as metadata, security, users and groups, subsites, and package management and deployment.
• The ACS 4 Core, which comprises all the other packages that ship with the kernel and are most frequently needed by users, such as templating, bboard, and user registration/management. The packages tend to be developed and distributed with the kernel.
• ACS 4 Application packages, which typically provide user-level web services built on top of the Kernel and Core. Such packages include those built by ArsDigita as well as external contributors. Application packages are developed separately from the Kernel, and are typically released independently of it.

This document provides a high level overview of the kernel package. Documentation for the other packages can be found elsewhere.

Kernel Components

Overviews for each of the Kernel components are below, with links to more detailed information:

• Precompiler Requirements

  The Precompiler provides a mechanism for extending the Java language to make using SQL within JSP pages easier.

• Object System

  The object system data model and API defines general mechanisms for application data and metadata storage that unifies many ad-hoc coding conventions that were used in ACS 3.x. The model defines a notion of object identifiers for naming application objects in a uniform way. In addition, object types and relation types generalize various mechanisms that we used in the 3.x user/groups system to provide more flexible data modelling. Finally, object contexts replace the old notion of scoping in ACs 3.x with a more uniform and general mechanism.

• Permissions

  The ACS 4 permissions system builds on the object model to generalize the scoping and general permissions mechanisms in ACS 3.x. Object contexts replace scope, and a data model and API supporting a hierarchy of permissions on objects replaces the "flat" data model in general permissions.

• Groups

  The new groups data model extends the old model in many ways. First, it introduces a new abstraction called a party that can represent either a person or a group. Groups then contain parties, and are thus form a hierarchy instead of being flat.

• Subsites

  Subsites provides a way to partition an ACS system up into one or more relatively autonomous pieces, each of which acts like a single web site.

• ACS Package Manager

  APM provides the ACS with a general mechanism for defining, installing, and managing independent components called packages.

In addition, the kernel defines the following extensions and APIs in AOLserver:

• Security and Sessions

  This provides low level support for secure session management and password checking.

• The Request Processor

  This is an extension of the standard aolserver request processing pipeline that provides authentication, authorization, and the ability to mount many different pageroots into one url space. The request processor also supports the developer support package.

• DB API

  This is an API layered on top of the standard aolserver database API. It provides automatic handle management, a nice interface to Oracle bind variables, and convenience functions for dealing with transactions and database errors.

• tcl Documentation

  This document describes extensions to tcl that help make our code more self documenting.

• Bootstrapping ACS

  How ACS bootstraps itself.

Pete Su
Last Modified: index.html,v 1.1 2001/01/21 01:38:17 bquinn Exp