# Package org.eclipse.incquery.runtime.extensibility

- Class Summary
  Class | Description
  --- | ---
  IncQueryRuntimeConstants | Utility class for IncQuery runtime constants, such as extension point identifiers.
  PQueryExtensionFactory | An extension factory to access PQuery instances from Query Specifications.
  QueryBackendRegistry | A registry component for storing all known query backend factories.
  QuerySpecificationRegistry | Registry for generated query specifications contributed via the plug-in mechanism.
  SingletonExtensionFactory | Factory to register a static singleton instance in an extension point.