[This is preliminary documentation and subject to change.]
Just-in-time installation relies on new Microsoft installation and component management technology. This technology allows each component of an application (including the core component) to be installed only when it is actually needed. Some components can be installed locally while others run from a CD-ROM drive or network server when needed.
Using this system installation technology, your application can effectively offer as deep and broad a feature set as your market demands while keeping the small local footprint that both users and administrators appreciate. Local hard drive space is often at a premium, and the less your application requires, the happier your customers will be.
Keeping the core component of your application small also makes running it over a network, with no local copy, much more practical. The application starts more quickly, consuming less network bandwidth.
The key to taking advantage of the benefits made possible by the new installer technology is to segment your application intelligently, so that core functionality is delivered in one compact component, and a wealth of supplementary features are delivered in additional components. Wherever possible, features that will be used together should be grouped in the same component.
An additional consideration in grouping features into components is to minimize installation of features that may be removed from your application through feature-set configuration. If, for example, your application offers a group of optional "Advanced Formatting" features that feature-set configuration could remove from the user interface, then it would generally make sense to isolate these features in a component or components that would never have to be installed if the features were not enabled.
For detailed documentation about how to take advantage of this new installer technology, see Introduction to New Microsoft Installer Technology.