These are terms that are often used in the Shared Dictionary Explainer.

Shared Dictionary (object and instance)

A shared dictionary instance is a hierarchical key/value data structure that can be distributed across a variety of machines and/or processes. An instance connects to (or creates) a Shared Dictionary server located at a particular URL. All data added, created or deleted on a shared dictionary instance is automatically sent and stored on the server, which in turn will selectively pass on that data to other shared dictionary instances that subscribed to particular key patterns.

Shared Dictionary Server

A shared dictionary server is the first shared dictionary instance opened at a particular network location. All other instances that connect to it will:

  • propagate their key/value pairs to the server.
  • tell the server what key patterns they are subscribed to.

The server will store the subscription patterns on a per client bases, and will use that information to propagate added, changed and/or deleted data to the shared dictionary instances that subscribed to a particular key patterns.

Key/value entry

A key/value pair within the shared dictionary.


An instance of a Subscription object, it is used to ensure that associated entries in the shared dictionary are kept up to date.


An event generated by the system when a subscribed to entry is changed, added, or removed. The notification event contains a “reason” field that explains why the notification was sent, be that changed, added, or removed. Otherwise, there are no differences between the types of notifications.