How to implement searching
Search functionality (and related functionality like Activity Streams) is automatically handled for you by the core of IPS Community Suite. You simply need to indicate that your content items should be searchable by implementing the interface:
Note that you must also have implemented the ContentRouter extension.
Changes after implementation
Content will be indexed and included in search results and the activity stream. The index will automatically be updated when content is created, edited, moved, hidden, etc.