# Glossary

activation
  Moving an object from the `GHOST` state to the `UPTODATE` state, load its pickled data from its jar.
data manager
  The object responsible for storing and loading an object’s pickled data in a backing store. Also called a jar.
deactivation
  Moving an object from the `UPTODATE` state to the `GHOST` state, discarding its pickled data.
ghost
  An object whose pickled data has not yet been loaded from its jar. Accessing or mutating any of its attributes causes that data to be loaded, which is referred to as activation.
invalidation
  Moving an object from either the `UPTODATE` state or the `CHANGED` state to the `GHOST` state, discarding its pickled data.
jar
  Alias for data manager: short for “pickle jar”, because it traditionally holds the pickled data of persistent objects.
object cache
  An MRU cache for objects associated with a given data manager.
pickled data
  The serialized data of a persistent object, stored in and retrieved from a backing store by a data manager.
volatile attribute
  Attributes of a persistent object which are not caputured as part of its pickled data. These attributes thus disappear during deactivation or invalidation.