Standard vs. Advanced Applications
A MSN® Messenger Activity runs in a confined program space, in which the application is only allowed to use certain specific resources.
Some Activities need features in addition to the basic features or allowed resources; these additional features are called advanced capabilities. Similar to the way ActiveX® controls can be signed with additional rights, applications can be granted certain additional permissions. In the Activity API Object Model section of this documentation, features that require special permissions are labeled restricted.
Advanced capabilities are available only to applications that have undergone careful testing and have been approved by Microsoft. Even then, each capability is permitted individually. It is possible to have an application that is only allowed to read the user name of the currently logged-on user. Another application may be able to parse any incoming instant messages from a remote party. Some advanced applications will require combinations of advanced capabilities, but the majority of applications will run inside the confined program space.
For further discussion on using advanced capabilities, see Obtaining Access to Restricted Features.