# Package org.eclipse.viatra.query.runtime.base.api

- Interface Summary
  Interface | Description
  --- | ---
  DataTypeListener | Interface for observing insertion and deletion of instances of data types.
  EMFBaseIndexChangeListener | Listener interface for change notifications from the VIATRA Base index.
  FeatureListener | Interface for observing insertion and deletion of structural feature values ("settings").
  IEClassifierProcessor<ClassType,InstanceType> |
  IEClassifierProcessor.IEClassProcessor |
  IEClassifierProcessor.IEDataTypeProcessor |
  IEMFIndexingErrorListener | This interface contains callbacks for various internal errors from the `base index`.
  InstanceListener | Interface for observing insertion / deletion of instances of EClass.
  IQueryResultSetter<KeyType,ValueType> | Setter interface for query result multimaps that allow modifications of the model through the multimap.
  IQueryResultUpdateListener<KeyType,ValueType> | Listener interface for receiving notification from `QueryResultMultimap`
  IStructuralFeatureInstanceProcessor |
  LightweightEObjectObserver | Listener interface for lightweight observation on EObject feature value changes.
  NavigationHelper | Using an index of the EMF model, this interface exposes useful query functionality, such as: Getting all the (direct or descendant) instances of a given `EClass` Inverse navigation along arbitrary `EReference` instances (heterogenous paths too) Finding model elements by attribute value (i.e.
  TransitiveClosureHelper | The class can be used to compute the transitive closure of a given emf model, where the nodes will be the objects in the model and the edges will be represented by the references between them.

- Class Summary
  Class | Description
  --- | ---
  BaseIndexOptions | The base index options indicate how the indices are built.
  LightweightEObjectObserverAdapter | Adapter class for lightweight observer which filters feature updates to a selected set of features.
  QueryResultAssociativeStore<KeyType,ValueType> |
  QueryResultMap<KeyType,ValueType> |
  ViatraBaseFactory | Factory class for the utils in the library: NavigationHelper (automatic and manual) TransitiveClosureUtil

- Enum Summary
  Enum | Description
  --- | ---
  IndexingLevel | The values of this enum denotes the level of indexing the base indexer is capable of.