By default, the actions available to the reader are those defined in the current event, however an actions availability may also be dependent upon other actions within in a scene, or be dependent upon certain items in the inventory.  Actions may add or remove an item from the inventory.  Items can be used to synchronize events between scenes. For example, a locked door can only be opened in one scene if a key has been found in another scene.

An actions availability can be extended beyond the event in which it is defined. An actions scope can be extended to an entire scene, or even to the entire story.  For example, actions that manipulate items in the inventory can normally be done in any scene.

Items can be used as a powerful mechanism to synchronize scenes and plot progression.  IS allows for 'hidden' items, items that are not shown to the reader, but are present "behind the scenes" in the inventory.  You can add, remove and use hidden items in exactly the same way as regular items.