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Notifications Package

+

+ +

The Idea

+ +
+ +Every program attempts to expand until it can read mail.
+Those programs which cannot so expand are replaced by ones which can.
+ +-- Zawinski's Law + +
+ +

+ +

+ +Every web-based application attempts to expand until it can send mail.
+Those applications which cannot so expand are replaced by ones which can.
+ +-- The OpenACS Corollary to Zawinski's Law +
+ +At some point, your web application - your OpenACS package, that is - +needs to send email to your users. The usual way to do this is to: + + +

+ +The goal of the Notifications package is to provide the +following functionality: +

+ +

+ +

Use Cases

+ +There are two main actors of the notifications package: + + + +

+ +Success for this package will be gauged by how many packages choose +to use it instead of going the ns_sendmail/iteration route. + +

Web Application End-User

+ +A web application end-user can: + + +

Sample Package: Forums

+ +The Forums package will need to use notifications, specifically as +follows: + + + +

Data Types

+ +

Notification Type

+ +A notification type is a category of notifications that fit a +certain application. "Forum Notifications" is one example. It is +conceivable that one application would have more than one notification +type if it performs very different types of notifications. + +

+ +A notification type may store additional data about the notification +itself. Thus, a "notification type" is also characterized by the specific +data it must keep track of. + +

Notification Request

+ +Given a certain notification type (e.g. "Forum Notificaton"), a +notification request is an association of a party, a notification +type, and an object for which this notification type applies. + +

+ +An example would be "Ben Adida requests a Forum +Notification on OpenACS 4.x Design": +

+ +

Notification Preferences

+ +A user or party may request certain preferences on their notification +requests. Some of these preferences will be on a per request +basis. Others will be on a party-wide basis: + + + +

Notification

+ +The notification is the actual message that goes out and +summarizes information that needs to be communicated. A notification +is the result of processing all the messages for a particular +notification type, and sending them to all the parties who have +requested this notification type, using the preferences indicated. + + +

+ +

Under The Hood: OpenACS Constructs

+ +The Notification package declares an initial notification_request +OpenACS object type. This is the base type for all notification +requests. Creating a new notification type involves subtyping + +notification_request. For ease of programming, an additional +table notification_types is kept which mirrors that +acs_object_types table for all subtypes of notification_request. + +

+ +Notification messages are queued as individual OpenACS objects. A +mapping table of which notification messages have been sent to +which users is kept. Whenever the pending list of users for a +particular notification is emptied, the notification object and its +associated mapping table rows are removed. There is no need to keep a +history of these notifications (not now). + +

+ +The process for delivering a notification is implemented as a +service contract in order to enable other means of notification (IM, +SMS, snail mail - who knows!). Instead of attempting to make the +notifications package too smart, we expect packages to come up with +different notification types (i.e. short vs. long) that will fit the +type of delivery in question. A long notification sent to SMS is +probably not a good idea. But we can't expect the Notification package +to be super smart about "summarizing" information down to a smaller +message. + +

+ +Email delivery is implemented using acs-mail-lite for reliability. + +

Supplemental discussions

+

+There are some additional docs and discussions on the forums at +here and +here +

+ +

© 2002 OpenForce, Inc.