| Interface | Description | 
|---|---|
| IBaseIndex | 
 Represents the index maintained on the model. 
 | 
| IEngineContext | 
 The context of the engine is instantiated by the scope, 
 and provides information and services regarding the model the towards the engine. 
 | 
| IEngineContext.IQueryBackendInitializer | |
| IIndexingErrorListener | 
 This interface contains callbacks for various internal errors from the  
base index. | 
| IInstanceObserver | 
 Listener interface for lightweight observation of changes in edges leaving from given source instance elements. 
 | 
| IncQueryBaseIndexChangeListener | 
 Listener interface for change notifications from the IncQuery Base index. 
 | 
| Class | Description | 
|---|---|
| IncQueryScope | 
 Defines a scope for the IncQuery engine, which determines the set of model elements that query evaluation operates on. 
 |