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

- Interface Summary
  Interface | Description
  --- | ---
  IMatchUpdateListener<Match extends IPatternMatch> | An interface for low-level notifications about match appearance and disappearance.
  IPatternMatch | Generic interface for a single match of a pattern.
  IQueryGroup | Generic interface for group of query specifications.
  IQuerySpecification<Matcher extends ViatraQueryMatcher<? extends IPatternMatch>> | API interface for a VIATRA query specification.
  IRunOnceQueryEngine | A run-once query engine is used to get matches for queries without incremental support.
  ViatraQueryEngineInitializationListener | Listener interface to get notifications when a new managed engine is initialized.
  ViatraQueryEngineLifecycleListener | Listener interface for getting notification on changes in an `ViatraQueryEngine`.
  ViatraQueryMatcher<Match extends IPatternMatch> | Interface for a VIATRA Query matcher associated with a graph pattern.
  ViatraQueryModelUpdateListener | Listener interface for model changes affecting different levels of the VIATRA Query architecture.

- Class Summary
  Class | Description
  --- | ---
  AdvancedViatraQueryEngine | Advanced interface to a VIATRA incremental evaluation engine.
  GenericPatternMatch | Generic signature object implementation.
  GenericPatternMatcher | This is a generic pattern matcher for any VIATRA pattern, with "interpretative" query execution.
  GenericQueryGroup | Generic implementation of `IQueryGroup`, covering an arbitrarily chosen set of patterns.
  GenericQuerySpecification<Matcher extends GenericPatternMatcher> | This is a generic query specification for VIATRA pattern matchers, for "interpretative" query execution.
  LazyLoadingQueryGroup | Initializes a query group from a set of query providers.
  MatchUpdateAdapter<Match extends IPatternMatch> | A default implementation of `IMatchUpdateListener` that contains two match processors, one for appearance, one for disappearance.
  PackageBasedQueryGroup | Package based `BaseQueryGroup` implementation.
  ViatraQueryEngine | A Viatra Query (incremental) evaluation engine, attached to a model such as an EMF resource.
  ViatraQueryEngineManager | Global registry of active VIATRA Query Engines.
  ViatraQueryEngineOptions | This class is intended to provide options to a created `ViatraQueryEngine` instance.
  ViatraQueryEngineOptions.Builder |

- Enum Summary
  Enum | Description
  --- | ---
  IModelConnectorTypeEnum | This enum represents the possible notifier types which a model input should provide for the ui.
  ViatraQueryModelUpdateListener.ChangeLevel | Possible notification levels for changes