The following is a requirements document for OpenACS 4 Subsites, part of the OpenACS 4 Kernel. The Subsites system allows one OpenACS server instance to serve multiple user communities, by enabling the suite of available OpenACS applications to be customized for defined user communities.

Many online communities are also collections of discrete subcommunities, reflecting real-world relationships. For example, a corporate intranet/extranet website serves both units within the company (e.g., offices, departments, teams, projects) and external parties (e.g., customers, partners, vendors). Subsites enable a single OpenACS instance to provide each subcommunity with its own "virtual website," by assembling OpenACS packages that together deliver a feature set tailored to the needs of the subcommunity.

The OpenACS subsite system allows a single OpenACS installation to serve multiple communities. At an implementation level this is primarily accomplished by having an application "scope" its content to a particular package instance. The request processor then figures out which package_id a particular URL references and then provides this information through the ad_conn API ([ad_conn package_id], [ad_conn package_url]).

The other piece of the subsite system is a subsite package that provides subsite admins a "control panel" for administering their subsite. This is the same package used to provide all the community core functionality available at the "main" site which is in fact simply another subsite.

The Subsites functionality is intended for use by two different classes of users:

Joe Programmer is working on the forum package and wants to make it subsite-aware. Using [ad_conn package_id], Joe adds code that only displays forum messages associated with the current package instance. Joe is happy to realize that parameter::get is already smart enough to return configuration parameters for the current package instance, and so he has to do no extra work to tailor configuration parameters to the current subsite.

Jane Admin maintains www.company.com. She learns of Joe's work and would like to set up individual forums for the Boston and Austin offices of her company. The first thing she does is use the APM to install the new forum package.

Next, Jane uses the Subsite UI to create subsites for the Boston and Austin offices. Then Jane uses the Subsite UI to create forums for each office.

Now, the Boston office employees have their own forum at http://www.company.com/offices/boston/forum, and similarly for the Austin office. At this point, the Boston and Austin office admins can customize the configurations for each of their forums, or they can just use the defaults.

A subsite API is required for programmers to ensure their packages are subsite-aware. The following functions should be sufficient for this:

10.10.0 Package creation

The system must provide an API call to create a package, and it must be possible for the context (to which the package belongs) to be specified.

10.20.0 Package deletion

The system must provide an API call to delete a package and all related objects in the subsite's context.

10.30.0 Object's package information

Given an object ID, the system must provide an API call to determine the package (ID) to which the object belongs.

10.40.0 URL from package

Given a package (ID), the system must provide an API call to return the canonical URL for that package.

10.50.0 Main subsite's package_id

The system must provide an API call to return a package ID corresponding to the main subsite's package ID (the degenerate subsite).

The Programmer's User Interface

There is no programmer's UI, other than the API described above.

The Administrator's User Interface

The UI for administrators is a set of HTML pages that are used to drive the underlying API for package instance management (i.e. adding, removing, or altering packages). It is restricted to administrators of the current subsite such that administrators can only manage their own subsites. Of course, Site-Wide Administrators can manage all subsites.