Architectural Principles

This document outlines architectural principles used in the design of plone.app.discussion.

Discussion items have a portal_type

This makes it easier to search for them and manage them using existing CMF and Plone UI constructs.

Discussion items are cataloged

It is possible to search for discussion items like any other type of content.

Discussion items are subject to workflow and permission

Moderation, anonymous commenting, and auto approve/reject should be handled using workflow states, automatic and manual transitions, and permissions.

Discussion items are light weight objects

Discussion item objects are as light weight as possible. Ideally, a discussion item should be as lightweight as a catalog brain. This may mean that we forego convenience base classes and re-implement certain interfaces. Comments should not provide the full set of dublin core metadata, though custom indexers can be used to provide values for standard catalog indexes.

Optimise for retrival speed

HTML filtering and other processing should happen on save, not on render, to make rendering quick.

Settings are stored using plone.registry

Any global setting should be stored in plone.registry records.

Forms are constructed using extensible z3c.form forms

This allows plugins (such as spam protection algorithms) to provide additional validation. It also allows integrators to write add-ons that add new fields to the comment form.

Discussion items are stored in a BTree container

This allows faster lookup and manipulation.

Discussion items are accessed using a dict-like interface

This makes iteration and manipulation more natural. Even if comments are not stored threaded, the dict interface should act as if they are, i.e. calling items() on a comment should return the replies to that comment (in order).

Discussion items are retrieved in reverse creation date order

Discussion items do not need to support explicit ordering. They should always be retrieved in reverse creation date order (most recent for). They can be stored with keys so that this is always true.

Discussion items do not need readable ids

Ids can be based on the creation date.

Discussion items send events

The usual zope.lifecycleevent and zope.container events are fired when discussion items are added, removed, or modified.