Tool architecture

Principles

The guiding principle in the architecture for the tool is that it should be based upon a collection of loosely coupled, highly cohesive components. A component-based architecture is attractive both from the point of view of ease of developing, testing and maintainance, but also with respect to the requirement for distributed development in an open-source project.

Extension points

Eclipse defines the notion of an extension point as a way that a plug-in can be extended by other plug-ins. This allows component-wise development of tools, which in turn leads to easier development and maintainance. We envisage a small kernel component which defines extension points. Functionality can be added to the core by creating plug-ins for these extension points. Note that plug-ins can also define their own extension points.

Kernel

The kernel should consist of the XML parser, an abstract syntax class hierarchy supporting visitors and management functionality. Eclipse has a notion of builders; a builder is a plug-in which is automatically notified when a source file is modified. This allows for efficient plug-ins, since a builder can either reread the whole parse tree, or it can just fetch the changes made since the last notification. We imagine that a large part of the management functionality will be related to handling builders.

Plug-ins

We envisage that all components beyond those in the kernel will be written as plug-ins. Thus there will be a type checker plug-in, an interpreter plug-in and so on. It is possible for a plug-in to define dependencies to other plug-ins; the Eclipse platform checks these dependencies at start up and only enables a plugin if all its dependent plug-ins are available.