# 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 captured as part of its pickled data. These attributes thus disappear during deactivation or invalidation.